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YOUR RESEARCH1st m96.3 rebuild I just have one question...?
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There's no doubt that winter blend fuels aggregate the issue, but the root of the issue is clearly related to running clearances and piston material.
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Jake has also mentioned that the cold weather problem is due to piston/cylinder clearances that are overly tight/small.
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It's very telling that his review stated that it was the smoothest running Porsche he had ever driven.
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Performed · outcome unconfirmed
Notice that I even have the crank gears fitted during the procedure..
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Performed · outcome unconfirmed · Original poster
I feel bad for any mid life crisis dude that buys his $20k dream 996 only to find out that his $24k engine failed before his serp belt needed to be changed because he lives in up state NY..
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Suggestion
Repairing just one bore makes zero sense to me, unless you want to be doing this all again in the future and in the mean time the engine isn't going to run optimally.
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Performed · outcome unconfirmed · Original poster
I feel bad for any mid life crisis dude that buys his $20k dream 996 only to find out that his $24k engine failed before his serp belt needed to be changed because he lives in up state NY..
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Suspected cause
Being a DIYer in the 996 world is not easy (it's a piece of cake if you have a 928), Those that know (for example Raby) have a business to run so they are not willing too willing to share everything they know and that's fully understandable but the main issue is all the checkbook enthusiasts here that "drink the cool-aid" for too long and then repeat what they read on the internet as if it was their own first hand experience.
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Rennlist: 1 discussions
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Outcome without a verified action link
This is not to say that you can be religious with maintenance and still not have it happen.
I rebuilt my 1st porsche engine which is this m96 3 chain motor and I started the engine up it runs way way better than when I took it apart but I got code 22 BANK 2 exhaust can over retarded... My observation is that when the crank pully is pinned at OD... Banks 1&2 ALL the camshaft slots line up at the same time... This this right or do I have to take the bolts out of bank 2 cams spin the crank 360 back to U6 and re time bank 2?
Set cam timing on bank 1 @ TDC, and complete the process. Then, rotate the engine exactly 360 degrees back to TDC, then set the cam timing on bank 2.
Do this in no other way.
I would start from scratch and quantify timing on bank 1 as well. The first rule of engine rebuilding is to assume nothing and to quantify everything.
Once bank 1 is good, rotate the engine 360 and do bank 2. Ensure the tensioners are pumped up and also rotate the engine at least 7 times clockwise and recheck both banks before calling it good. The tools must fall into place with the crank pinned @ TDC for the timing to be spot on.
So as I understand it ALL the slits that line up the cams should NOT all be perfectly lined up as the same time. I have to line the bank 1 cams up then rotate the crank 360 and then line up bank 2 cams.. So right now I'm a whole 360 degrees on bank 2 which sounds insane but I am I only took apart bank 2...
This is a common mistake, you have phased both banks the same, making 2, 3 cylinder engines!
The offset slots should be opposite each other when timing is properly set. Let me guess, the engine only ran on bank 1 after reassembly, and while on the starter it was very difficult to turn over?
Yes that what I thought so now I have to find a way to turn the motor 360 and retime bank two easiest way possible? Idk? And yes this motor came in blowing huge clouds of smoke and slapping really badly this is my first porsche engine I've build so sorry for my ignorance your help is greatly appreciated...
This is my first experience with a porsche of any kind really... So I called every porsche parts place around with the same answer $7.5 for both cylinder halves and $718/piston... I called L&N and didn't like there price either also they were on a waiting list.... So I sent the block to my machine shop guy he bored it .030 recoated it and ordered 3 .030 Pistons from JE that were 28 grams too light so we got 28 gram heavier wrist pins put it all back together and almost had a running car!! I missed that one step tho!!!
Till the next poor guy buys it unknowingly and ends up screwed. Do the Porsche world a favor and keep working on whatever you were. So much for integrity.
^your not helping sir!!^ Jake thank you very much for your help nobody around me touches these motors not even the porsche dealer....I know that's not exactly what u wanna hear but this guy bought the car smoking at a auction which was his first mistake then said we have to fix it cheap this was the solution in all actuality it's goin to run just fine until the IMS bearing blows.. I was put on the spot and given a budget so I did what I had to do... Sorry if I made people throw up it wasn't my intention I just needed some help
And I won't help you anymore, either. I refuse to be a party to such practices.
So just pass the buck on to the next guy? At least the first guy bought it knowing it had an issue, because it was smoking, the next guy won't be so lucky. Will it be sold as a 3.7 liter? I doubt it.
The most expensive fix that can be made is the cheapest one. Just ask the guy who buys this car and it fails again. It will fail again. When he calls me, and he will call me, I'll be sure to reference this thread.
The factory cylinders are NOT coated, they are Lokasil. I don't know what you coated them with, but the chances of it working long term are slim.
This thread is going in my newsletter next week, just to prove that all these cars need a very specific engine focused PPI before purchase.
Uhhhh.....this thread turned interesting in no time. I was just about to post that I made the mistake of making mine a double 3 cylinder when I was putting it together 2.5 years ago. Noticed something was wrong when it was hard to turn the engine over by hand. Had to pull the bank 2 cam cover to re set it. If you worked on engines long enough (doesn't need to be Porsche) you will know something is off/weird when it takes stupid amount of force to crank the engine over by hand.
Jake,
In this case, what is the appropriate fix? Would it have been to have the machine shop replace the cyl. sleeves? Doesn't LN sell replacement sleeves?
Yes, but the LN fix replaces the entire cylinder. The only parent material that remains is the bottom most portion. This is only retained to assist with aligning the replacement cylinder.
Now, what really sucks about this instance is what is more than likely occurring on bank 1.
Its failing too
(I would assume based on my experience). It just hasn't showed symptoms yet, because the piston pin offset is more favorable on bank 1, than bank 2. So, more than likely all this work to bank 2 will be trumped by bank 1 at some point.
Yes, LN cylinders would fix this, BUT they cost real money and have a lead time. Neither of these things were important to the original poster, so he just half assed it back together. Now you guys see why I am so damn picky about my components. There's a lot more guys like this one out there.
These engines see cylinder failures like the one in this thread when used in cold temperatures. This year so far we've had a total of 22 engine failures logged in the system all with the same symptoms, and all were driven in cold. This is not "new" news, we've known about this for over a decade.
Jake, thank you for taking the time to continue to post these valuable pieces of insight. You clearly demonstrate a valuable member of the Porsche community.
Jake has also mentioned that the cold weather problem is due to piston/cylinder clearances that are overly tight/small. What are the chances of getting slightly smaller pistons/rings to address this problem?
Thats a band aid, IF you could get the pistons in that size. Mahle and KS will not supply these pistons to anyone other than Porsche in fear of losing their contracts.
The only proper fix is a different piston material coupled to the proper running clearances and moving away from a Lokasil bore.
What would have been wrong with using Nikasil, or another coating? Was there a reason they went with what they did? Then, at least at a high level, the piston and cylinder are the same material and heat/cool at a similar rate - are there big drawbacks in production or wear that come up with it?
Just wondering.
If there is a good thread about this or some online article please let me know, I didn't do a huge search.
Hi Jake. Long time listener, first time caller (at least to a thread you were involved with). I was just wondering what is considered "too cold" for these cars in your opinion?
Mine is stored in the winter, but once it gets in the mid 30's ill occasionally drive it.
Thanks, and sorry for the threadjack!
Search the forums for my opinions and observations on cold operation.
As far as what the factory did, only they know that. I have a lot of comments that could be made, but I won't make them.
Jake - I would run and hide from this thread! This is really going nowhere fast. If and
when
it comes time to rescue my M96 engine I plan on having it delivered to you in the Budweiser Beer Wagon with a marching band out front.
Well I would't say that so much as far as the band and a beer wagon only to Jakes shop - but that there are only a few paths to rebuilding one of these and both of those paths require the proper parts - and those parts are expensive. Like it or not.
I'm sure the OP, if they went through that much trouble to be cheap, could have also done it the correct way if the client wanted to pay for it and wait for it.
So...ummmm...what you are saying is this guy is doing it on the cheap....ummmm...because it may still work for about 10 miles....ummmm...and has no practical idea what he is doing...and ummmm...ummmm...ummmmm wtf
From what I have read and gathered they went with Locasil strictly because of cost. Nothing was wrong with using Nikasil, it was a little more expensive, if I remember correctly.
Mike
That's where I was going with it too, or that at the time they thought what they did was good enough and gave it a shot.
Sometimes you can't test for everything and anything that comes up.
Client is doing it cheap, not sure the guy has "no practical idea" as I'm sure they know how to work on engines, but maybe that they have lower morals or something and just did the work so it could go down the road.
Also, I guess that doing things like that is somewhat common (other forums I think talked about iron bores) when clients hear how much things cost.
I used to live in Boston.
Daily drive it.
Car used to be parked outside in the bitter cold winters ALL winter long
Winters get single digit Farenheit days.
Over 50K miles and NO bore scoring or cold related damages at all (I did have an IMS bearing let go but that's a different story).
My neighbor -just outside of Boston - same terribly cold winters... (who refuses to join rennlist):
parks his 996 outdoors ALL year round. Daily driver 40miles per day
Over 120K miles on the odo.
Only changes oil (mobil 1), changed an AOS, and spark plugs and air filter, brake fluid, pads.
Everything else is original including clutch and rotors. Cheapest to maintain car he's owned.
Some else wrote "It's a car - not a Faberge egg".
Jayzus.
As a lot of peeps had said already, bore scoring is going to be the next IXX paranoia.
Some people will get lucky with it, others won't. I've also known quite a few people, including people living in Norway/Sweden/Russia that have over 100k or even 200k miles on their cars driven all year round with no issues. I also have talked to quite a few shops other than Jake's to know that this does seem to happen to some people driving them in cold climates. Just like the IXX, it seems to be all over the place with no kind of rhyme or reason anyone can really gather with any amount of certainty. Some get lucky, others don't.
Just like with IXX risk mitigation, some will elect to park it during any cold winter to be on the safe side while others will continue enjoying it year round.
Oh boy, let all the threads start again....
The scoring is definitely something that has no rhyme or reason, except cold being a common denominator. We don't get these calls from Florida, or south Texas, or other warm climates. I have gotten calls from SoCal though, and Tony Callas has a failed cylinder at his shop right now in LA... I think that car came from a cold climate, he is checking now.
This only happens to the engines with forged pistons, and we know why it happens. There's no doubt that winter blend fuels aggregate the issue, but the root of the issue is clearly related to running clearances and piston material.
Once an engine gets some wear on it, and the cylinders go more oval, and the piston skirts start to wear, the components gain operating clearance and they don't die.
I had two calls today, one from a 4.8 Cayenne, the other from a 3.4 Cayman S. Neither guy had a clue what had happened when he called me, but I took the symptoms right out of their mouths once they said a few sentences. I had to keep asking the Cayman owner if he was still on the phone, because he was so quiet. He said that he just couldn't process the fact that I told him exactly what happened verbatim.
Every year the cylinder calls and posts roll in just as spring opens up. The colder the winter, the more calls we get, and the further south they come from. That no surprise as I saw zero degree here in N Georgia for the first time in my life this winter.
I haven't had an IMSB failure call in 2 weeks, but we've had at least 10 cylinder failure logs made into the ledger.
The sad part is unlike the IMSB, there's nothing that can be done to curb this failure at the present time. There was a time when this was the case with the IMSB, then we conquered it.
No preventative will help, and no oil will help. The equation is wrong and till this point I haven't figured out a true way of avoiding this failure.
Mine was driven every day, Canadian winters and tracked every summer since 2003
Every since I've had the car since new it always burnt oil and I've had to change catalytic converters every 2nd year of driving. Aprox 12k km per year.
at 76k km started tapping and noticed it burning more oil then normal, I had my idle tensioner replaced due to squealing and then noticed that sound replaced with ticking/tapping.
at 106k km, my an ignition coil went, I drove about 5km to by shop and had them all replaced, I really noticed the tapping sound from that day onward, the tapping was louder and seemed to be burning more oil, used to go through at least 1 liter a track weekend, started blue smoke under cold startup in colder weather conditions but was fine after it's warmed up. Taping would some times get quieter or stop after running it hard.
and 120k km I had it looked at, #4 scored and piston crown touching head, all cylinders had oil pooling and plugs all looked dirty liky they are burning oil. It burns lots of oil, did one track weekend after this and was adding oil every hour to top up. That was my last track day with it. Smoke every time I started it up, probably topping it up to much.
Had the car dyno'ed and it came in at the same at aprox the same other 2 other 3.6l 4S, pretty standard hp/torque for this engine and nothing special. Since that time both the other 2 4S's that were on the dyno that day did not show any sign of problems and no tapping but both have died since then and had their engine rebuilt or replaced.
Now at 134k km, burns about 2 bars per 200km. Tapping is still loud but seems to go away or can't be heard under load, just noisy at lower rpm. Lots of blue smoke under cold startup but fine after it's warmed up all though it blows smoke even under warmer weather under cold start conditions, might be because of the long intervals between driving it. Doesn't really get driven anymore.
When I do drive it, the car still pulls hard and torque is amazing for this car. I drive the crap out of it to burn out of the gas occasionally. Drive it on hour long trip and have lot of times for 30-60 seconds maybe longer right up there at redline and it just keeps going.
It's probably got over 30-50k km on it like this. no rhyme or reason
How about a simple coolant or an oil pan/sump plate heater (like the TDI guys use)? Plug it in at night, set the times to come on 2-3 hours before the morning and that's it. All one needs is an outlet to plug the cord in. The engine gets coldest when sitting over night. Once it's driven and then parked for a work day, it usually doesn't cool down as much as it does overnight. Diesels don't like cold and my DD has been a TDI for over 10 years so I have some experience with how much and engine cools down from sitting.
This is what some people have been doing but it isn't ideal nor an option for everyone.
I'm just purplexed as you have some people that have driven it over 100k+ miles in every winter for years without any symptoms and no oil loss between OCI, then you have others that's had issues even with one harsh winter. As with some Porsche owners, I suspect their maintenance like OCI might be suspect and I've found that some often try to blame the car for their lack of maintenance or attention on certain things. This is not to say that you can be religious with maintenance and still not have it happen.
no rhyme or reason...
However I do predict if this issue or the broken timing chain issues blow up, the 996 will always remain low for resale. I just don't wanna see a guy in the hood living on food stamps driving one. lol.
A real pity...
I live in a nice moderate to hot climate so my car never really sees cold weather like you guys talk about. If I did live in the colder climates I would look into some kind of engine heater, oil, water or whatever. I AM SPOILED LIVING OUT WEST.
The block heater has already been developed and was already offered. It included an external pump (also 110V) that moved the heated coolant through the engine as well, else it didn't work at all. It cost around 1500 bucks and less than 10 were ever sold.
The issue has remained that the pistons expand too quickly. In class about 6 weeks ago I was illustrating why you never build an engine in a cold room. I had one piston sitting on the bench and I grabbed it up and could not slide the piston pin into it by hand. I had an attendee how the piston in his hands for 30 seconds and the pin fell right in. Ltusler was there, ask him!
Until the other bank of cylinders fails, or until the "coating" that was used fails, or until it shakes it's self apart from poor combustion balance. Never mind that the pistons were statically weight balanced, do you actually think that the engine will have consistent combustion when every other cylinder that fires has more compression ratio, and a larger swept volume than the cylinders that fire before and after it?
The knock sensors and safety retardation have to be going crazy! Whats the rough running index on this one? I'd expect it to be triple digits!
I learned when I was a kid that anything that would turn and build compression would run, but what happens after that only time will tell.
Lots of things in this business come down to saying NO! When someone wants to cheap out on something and just pass it on to the next guy, lots of us just have to say no. No one held a gun to the head of the guy holding the wrench and made him take this job on.
What about an "oil pan" heater? Have a billet plate machined or cast to fit into the webbing of the sump plate (the other side would be flat to accept the bonded electric heater plate). These have no moving parts and work great on inline of V engines. I can't see why it wouldn't work on flat sixes (they have oil in the sump so the heat will be transferred and then the hot oil will heat the rest of the engine from the inside.
Nikasil and we had je custom make us piston and also had the skirts coated to run with the nikasil. This was not a "cheap" fix by any means the guy bought it to flip it well he not making much if anything on it now!! I do have morals I've built plenty of high dollar engines and I'm very well known in my town for doing fantastic work and trusted by all... I was given a job with a budget and this was my solution fix the cylinders that failed... If you think the engine or computer is going to notice the <.25 cube difference your nuts because I put it together and the car purrs it runs and drives like a porsche should!! The only problem I have is the construction of this engine I never heard of a $25k engine failing because it was cold out this freakin engine still had the orignal serp belt on it!! The belt lasted longer than the engine which lasted 42k miles hopefully someone at porsche got fired for this!!!
That really hurts man I do great work I know I do great work how about I sell u a table seems to be the only thing these porsche engines are good for.. The belt lasted longer than the engine its self
I think all the negative comments are because you are flipping the car. You could be unloading a disaster on someone. I would love to see how this repair works long term. Some people think the motor is going to implode. If it doesn't and you are right there would be another alternative to repair the scored cylinder problem. That would be great. If it doesn't and its your car then it's a risk you took. But flipping the car we will never know.
I want to see more of the work that was done to the engine. I don't like to jump in and judge people based on a feeling. I want to see the work they did. Being a DIYer in the 996 world is not easy (it's a piece of cake if you have a 928), Those that know (for example Raby) have a business to run so they are not willing too willing to share everything they know and that's fully understandable but the main issue is all the checkbook enthusiasts here that "drink the cool-aid" for too long and then repeat what they read on the internet as if it was their own first hand experience. This is the reason I put my engine fixing project on the Canadian forum 2.5 years ago.
What the 996 world needs is a shift in demographics (I think it will happen pretty soon because the cars are getting really cheap) where most of the owners do their own work and are more than willing to share their knowledge with everyone else. Go look at the 944 or the 928 forum, that's what being a gearhead is all about, not this crap that's going on here. After all, that's what Rennlist should be about and not just one giant advertising platform for a engine builder or two.
Like I said before we bored out past the scratches a lil before .030 and JE made custom Pistons and got it nikasiled... which I think are the same as LN Nikies right? this engine actually is quite easy to work on and build the only special tool I used was over nighted from Baums tools the wrist pin clip installer and the motor is literally held in by 4 bolts came out in < 3 hours so all in all this was a routine engine build and I've built plenty of engines all kinds of engines and even if it was a customers car I'd stand by my work and I know this fix will hold up how could it not explain?? Brand new machined cylinders and brand new forged pistons sounds solid to me as for the other side it made no slapping noises and made no smoke so only time will tell... My money is on my fix working
Are you going to offer a warranty on the rebuild that transfers to the new owner? Because that's how you show you have faith in your work. Anything less is just words.
Not an engine builder here. Just reread the thread. Bored at a volleyball tournament. But it sounds like bored out cylinders 1-3 and put in bigger pistons. Can you do this? Not specifically for a 911, but a boxer engine in general. Seems like there would be a weight difference and a power difference.
No At the end of the connecting rod everything weighs the exactly the same identical even the compression ratio was the same everything was compensated for boring it out a lot of thought when into this fix and a new engine was 24k the used engine was 14k L&N nikies were like 6k and this fix was like 3500 I think I only fix the cars infact I don't even work at the shop he calls me in it engines tough electrical diags and diesels I work at the local high school so this is the fix we came up with and we went with it and it ran beautifully
I wouldn't send a 996 to the block with 2 pistons slapping and smoking like a pig I wouldn't send a 996 to the block with a fix I didn't think would fix the car... My name isn't Roy L. Fuchs!!!!
If this were a solid method of repair then why auction the car off? The owner should be stoked!
In (a weak) defense of the OP, single cylinder repairs are somewhat common on air cooled aircraft motors. But in those situations the entire removable cylinder is overhauled/renewed, not bored out and lined.
I would also not be surprised that it ran "fine' with a mismatch cylinder. Back in the "just fill it with gear oil and put sawdust in the tranny" days my dad helped a guy take apart a ford 302 where someone had removed an entire piston and rigged it such that it ran. GM had the 8-6-4 "technology" and a five cylinder Audi, VW, Volvo idles smoothly enough.
Having just held 100% of the guts from my engine in my hands, I would be shocked off there weren't quite a bit of collateral damage from loose metal.
This guys is a wholesaler thats what he does flips cars and in this case you can just replace half the engine I called parts places they wanted $7.5 for just the cylinders and 718 for each piston I believe the parts for this fix totaled maybe 3-4k something like that and L&N wasn't that helpful this was a great idea and the only reason I shared was because I was proud of my fix and happy my engine ran beautiful after I times it up right... And the rest of the motor was cleaned out throughout and the other side looked great for the price of a head gasket we checked..
Nothing else needs to be said... Thats the kind of guy who don't give a damn about a Porsche, or the person who has been wanting one all his life, only to buy one and have it fail.
Karma is a mean bitch.
Yes but this whole thing is about me not him who cares what he does he flips cars that's what he does all I needed to know was how to time this pig up so I could take a junk porsche and make it a not junk porsche... I feel bad for any mid life crisis dude that buys his $20k dream 996 only to find out that his $24k engine failed before his serp belt needed to be changed because he lives in up state NY.. Thanks for everyone's comments the car runs great
How were the bores recoated? Again, if you did this on all 6 cylinders with recoated bores and custom pistons what is the issue? I'm just asking as I'd like to learn.
Anyone?
Ouch. That hits home. I think that is why I am so fascinated by this thread. Few more thoughts. I know I said I am not an engine builder, well I kind of lied. But I only rebuild real engines. Singe cylinder Kohler's for my Wheel Horses. All iron. Aluminum? Nikisil coating? Liners? More than one cylinder? Nope. Not me.
My problem is you have three bigger pistons on one side. Even if it's a little they have to make more power. And not sure if center of gravity of a piston matters but it has to be different. And things like clearances (which Kohler publishes and from what I have read Porsche does not) are a problem. I have learned that they make a difference. The single cylinder cast iron beasts will run with about any clearance. But the difference between running, running well, and running for years is huge.
I really would like you to keep the car and drive it. And after 20K miles come back and say I did this to the engine with these specs and the engine is perfect.
But I get it. Guys buys car for 5K non running, puts 5K into it to get it running across an auction block, sells it for 12-15K and makes a little money. New buyer drives car a while and engine blows and he gets on line and finds out this is what these engines sometimes (not often, but sometimes) do and either sells it as a non runner or fixes it right.
And we never know.
No, this isn't a new fix. Anyone with low enough standards could have done this years ago.
So, why even bore the block at all? Just find a block half from another engine and bolt it on, it doesn't even have to be the same displacement!
My experience is that IF one bore does this, the rest are right behind it. Repairing just one bore makes zero sense to me, unless you want to be doing this all again in the future and in the mean time the engine isn't going to run optimally.
Maxtegroom, please post a screen shot of the rough running index of this engine. I want to see it.
Lets do some ballpark math here. 0.030" increase (assume he meant diameter) on a 96mm piston is 1.6% increase of the swept volume. The chamber volume may have changed due to different piston crown shape. If it stays the same, the c.r. will drop. If the new piston is modified to keep the stock c.r., all bank 2 cylinder will be 1.6% more power. If the c.r. drops, this 1.6% maybe offset by the c.r. drop.
Many variables in play here but is 1.6% power difference significant in any case? I would guess that can be easily absorbed by the DMFW?
I think it will run fine with no seat of the pants difference. I think its a mickey mouse fix to a tired engine, there will be more problems. These cars require good maintenance and money to fix things properly if they are to stay as they were when new. Fixes like this lead to the car eventually becoming a track car and then after a crash or some other mishap it becomes a parts car. Until then someone who needs a bargain will buy it and drive it. Most people like that will not have the money to maintain it and wont spend unless there is no other choice. After all is said and done I think who ever owns it can do whatever he wants without any of our opinions mattering anyway. I've been in the trucking business for 48 years and have seen every mickey mouse repair that could ever be thought of. Its amazing how many actually work against all the odds.
If having specs this loose didn't matter, the bore sizes of engines could be +/- .75mm (.030) and no one would care. Thats not the case.
Yes it matters, everything matters. This is a precision machine.
I think its statistically insignificant. Yes it's not optimal (aka perfect) but it won't matter that much. How many engines run "fine" and yet have scored cylinders? The only signs are the piston slap and the smoke. To a perfectionist this, and many other things, are not a solution. As much as I like to cheap out, I would have went with the another used case half with used pistons route.
Will using a half casing from another engine create other problems? What if they don't line up perfectly e.g., rms, ims casing holes. I think the casing halves are machined together from the factory and not to be mix and match with other casings?
There are no coatings!!!!! Lokasil is not a conventional coating. Nikisil is also not a coating, it's a plating!!
Also, if the work would have been comprehensive the whole engine would have been torn down and all 6 cylinders bores the same diameter and treated the same way, using the same Pistons.
If this would have been done the 3 new Pistons would not have needed 28 gram heavier wrist pins. All 6 pistons would have matched and you would not have all the issues we've gone over here.
But that was too hard and cost too much, it was easier to just half way do the job. I see engines half way built like this all the time. It was much better before people were working with these engines. Today we see engines molested every week, a few years ago they were all virgins.
No, using block halves from two different engines is not advisable and has its share of issues. That said, it's a hell of a lot better to take those risks and experience that compromise rather than putting in mismatched Pistons. I am astonished that a few of you can even remotely understand how anything good could come from this practice.
Would you buy a car knowing it had mismatched Pistons? What if you bought one unknowingly?
Somebody will be buying one unknowingly soon and I hope like hell they are members of this forum!
The cases are line bored in the factory, the case halves are together when the various holes holes split along the centre line are machined, I would imagine if you got a bad match from another casing half you might get oil leaks as the main seals would not seat properly??
It was a cheap way to half *** fix the engine. In the long run or short run it will end up costing more than if it was done right. I hope the buyer understands about the half *** fix before he lays out his money, at least if he is aware all is fair. If I bought a car without knowing anything about 3 cylinders having different bores and heavier wrist pins to make up for lighter pistons etc there would be problems when I found out if I could still find the seller.
What if it holds up and runs fine for many years to come? At this time we don't know if it will or will bot last. Everything is a guess. The only way you would.know an engine had work like this done is if something fails and it needs to be taken apart. There is nothing you can do to the PO even if you knew he did the work. You can bark and thretten but nothing will hold up in court.
I'm quite sure that is exactly how i got here given the s*** show that i found taking my 986 apart.
Jake, if i could ask a couple of questions. My plan for engine #2 is to pick up a set of case halves and ship them to LN for sleeves. Do they check/correct the distance and alignment of the crank to IMS bore you referred to earlier? If so I'm assuming they would need my bearing carrier in hand to do so, right? Is it even possible to align bore the crank centerline of the bearing carrier? It seems very, uh, "substantial" so maybe that part is redundant.
Thanks tons for your continued input to these threads.
With a bore scoring failure is there any concern about where the actual metal from the cylinders went? I ask because it seems like something that could bite you down the road post rebuild.
Absolutely. The microscopic debris is what hurts the most, as it is suspended in the oil and delivered throughout the engine.
This engine has many things that are not in its favor. Let's remember, the guy assembling it also didn't know how to carry out the cam timing procedure.
Yeah. Runs perfect, after I gave him the silver bullet!
Damn, I really never should;d have replied to his post with any help at all!
"Damn, I really never should;d have replied to his post with any help at all!"
Jake: I have watched the progression of this post strictly due to your involvement. There was no way at the start that you could have know this was a hack job. Stop beating yourself up. As you stated, you see the "cheap" repairs in your shop all the time and that there will always be those who will try to do things on the cheap. Very frustrating for one such as you who actually knows better. It is discouraging to us all. I used to race sprint cars and if we "dropped a cylinder" the whole deal was rebuilt not just repaired! Keep doing what your doing and know that the information you share here is valuable to those who want to do it right or just to understand/learn.
Thank you.
As this fix is somewhat unconventional to these types of motors, I'd be curious as to the long term reliability myself. It's easy to speculate and guess.
I'd really like the OP to list the last few numbers of the VIN here so that any future owner that comes here with any issues(if any) can be tracked to this repair.
So what that he didn't know the cam timing procedure is unconventional? It's easy to miss if you never done an M96 engine before. If you didn't tell him how to set it up correctly, I would have.
"Damn, I really never should;d have replied to his post with any help at all! "
How does that saying go?..."The road to hell is paved with good intentions" (I think that's it, or something similar) If it's any consolation, at least you tried to do the right thing
Sure its conventional, people have been half assing mechanical things as long as mechanical things have existed. It seldom works long term.
Now, you have to understand that I grew up doing all sorts of crazy things with engines, and it was't just Porsches... I was once across the border into Mexico in my old sand rail and got it a little too hot, wiping out a cylinder. I removed that cylinder and we made our way into a small town near the border where I found a VW shop. They didn't have a 92mm cylinder and piston, but they did have a 90.5mm. Both the 90.5 and 92mm cylinder use the same outside diameter cylinder, so the case and head cuts are the same.
I returned to the buggy and commenced to wash parts with beer and reassemble them. What else are a few Marines in the desert going to have with themother than beer? After reassembling it I drove another 45 miles back to the border without any problems other than a hellacious vibration. Once back to the auto hobby shop at El Toro I repaired it the proper way.
The difference with my story and this one, is I didn't do this with the intention of selling the car, and I did it because I had no choice and no way to get home otherwise.
Again, the proper method of addressing this would have been to disassemble the entire engine and apply the same "fix' to all the cylinders. The other bank is scoring too, it just hasn't shown symptoms yet. Disassembling the entire engine would also have allowed all the debris from the failed cylinders to be removed from the rest of the engine.
Again, who in this thread would appreciate buying this car unsuspectingly (at full price) and learning later that this was done? Thats what I thought.
Am I right in saying lockasil is a cast cylinder and not a plating I think so?
Is it feasible to bore it out then re finish the surface and fit the oversized Pistons , obviously better doing both sides for balance!
The downside would be a thinner cylinder wall which would be more prone to ovality and d chunk ??
Other forums talk about the walls being right on the edge after the 3.4 engine, so boring them out would make issues worse as far as scoring - at least according to them.
I'm with you on the balance part though, only if that bank was bad. If it's good may as well save it.
That's just it, and it's not really going to cost someone that much more since those cylinders were shot anyway. Although getting into the car it would be nice to know about this fix...
What was the weight of the piston that you put into that beetle engine? Was that the reason why is shook and not so much the slightly larger displacement?
Do they sell the banks seperate or together?
It seems that the worst that would happen is the "fix" fails in a few years, should run and work ok in the mean time, and then the new owner would be in the same place with the same options. Again, as long as it's not sold as new engine or rebuilt engine then I just don't see an issue with this. Who knows, the fix could be fine and a timing chain fails...
Typically that piston is about 7gr difference.
The weight difference is one reason for the vibrations, but combustion balance equates to more.
Those who have never dynamically balanced an engine to a tolerance of .2 oz./ in. and built it up, then tore back into it and balanced every chamber volume and every deck height to the nth degree can't equate to the differences I am speaking of.
The best dynamically balanced engine will still not operate as smoothly as one that also considers combustion balancing from blueprinting.
Here's what I balanced last night, dynamic assembly from a '76 930 engine I am building this month..
I spent the money for the best balance machine I could find. The balance machine isn't everything, the machinist running it and the assembler who assembles the engine are both key players. Thats why when I build something, no one else touches any part of it.
That's nice but it's an overkill. Even the factory doesn't go to that level. Your level of expectations is higher than the factory specs so if someone does something less, it's right away not accaptable to you. Engines can and do run well without taking them to the Nth degree.
0.2os is about 5.7grams but it sounds cooler inndecimals.
That's .2 oz per inch of measured component radius. That's a big difference when dealing with something like a flywheel that's 10" diameter. To achieve this both measured planes must have an accumulative imbalance of less than the tolerance that's set by the user. In this case that's .2 oz / in.
Notice that I even have the crank gears fitted during the procedure.. When this pic was taken I was just getting ready to add the crank pulley to the rotating mass and correct it. This is t a race engine, it's just a street engine.
Now, that said, damn right the factory doesn't do this today, but they did yesterday. In fact this engine was all original and unmolested as a virgin when I got to it. Until I added the new pressure plate I didn't have to correct anything to have the unit balanced to tolerance. If I do this with an M96 we are whittling parts right off the bat.
So, if I were to build a stock engine and use two different Pistons in two different bore sizes you guys would accept that? Raise your standards people, we are working with a damn Briggs and Stratton here... Even if I was, Id still balance it. I balanced the engine for my lawnmower a couple years ago when I had to tear into it!
Overkill? I would say not... Just because most everything to day is built to "good enough to get it out the door/sell it" doesn't mean it the right way to build something. Jake has created a business model that allows him to build things to a very high standard and get paid accordingly. Kudos to him for sticking to his standards! His isn't the only way, but it's clearly the best way if you can afford it
When I first got my car I joined my chapter of PCA. I'm not really that social but I thought I would be accessing a local technical knowledge base (instead of a bunch of fender polishing doctors) that would be of help when I was elbow deep in my crank case.
I recall in my early reading where someone brought their Raby engine car to a track day and let one of the club seniors drive it. It's very telling that his review stated that it was the smoothest running Porsche he had ever driven.
That is the result of mass balancing and volume balancing exactly as he describes above.
Jake's engines may be out of my price range but I understand that he is building his reputation not on "good enough" but on the best engine you can buy.
If you can build it so that it runs good and holds up for many years then I really don't care much how you do it. The goal of repairing something (and the OP did just that) is already a compromise because a full rebuild, properly done, is always better than just fixing an old engine but it cost a lot more too.
Your OCD of balancing engines to the Nth degree is not required in every engine out there. You do it because you can't help yourself. Balancing an lawnmower engine?!?!?! Give me an Fn' break! Sure an engine should be balanced as close to perfection as possible but in many cases this is not a requirement to make them last.
What's the definition "everything today is built to good enough"?
The cars of "yesterdays" are are built to much lesser standards than today. 30 years ago cars would last half as much as they do today. 130K miles was usually the end of most cars back then. Now look at your local classifieds or go to the local junk yard as see how many miles those cars have. The air cooled 911s yesterday have/had their fair share of major problems too but because the internet wasn't around yet, we didn't hear much of it unless someone published it and that wasn't happening much.
I'm sorry I jumped on the person and said morals and cheap before hearing more about what they did.
I'd work with them in a heartbeat if they were local and some work came up. Maybe not doing what they did (since I'd more than likely find the money for new parts) but I'd trust them to put everything back together and/or be a resource if I needed help on something.
It's hard to find a shop that will do that kind of work on any engine that walks in or one off projects like this.
I've said enough.
It's a sad day when it's acceptable to mismatch bore sizes and piston materials inside the same engine. I don't care if you work on Chevys, or Porsches, that's unacceptable.
Patching something up for yourself is one thing; knowing it's being done to pass it on to another unsuspecting buyer is another.
my assumption is that this hodge-podged engine will beat itself to death eventually. more displacement in one cylinder bank is the largest of the issues. this sucks for the unassuming future owner.
This is a source reference. Confirm exact model applicability in the original material.
