Will the 3.4l cyl.heads fit the 3.6 block?

I know that the timing chains are different. I'm just figuring out my options for building a "better" engine. And calculating the possible cost's for engine build. Hp aim is some where near 100hp/liter so in this case 360hp. I wan't the engine to have good low end torque, so that's why the larger displacement. I'm in no rush with this one, and hope to hear some opinions how to achieve the hp goal. Car must be N/A so no turbos etc. (registration problems)

Maybe (and probably) a stupid question, but why not go for a fairly simple X51 upgrade to the 3,6 with possibly upped compression to get the last 15 or so hp out of it ?

I think that I need new ecu and wiring harness for the X51? How much would the X51 conversion cost? Like I said ,I'm open to suggestions.

What do you have now? year ? model ?

Oh, 1998 C2 manual. Engine that I have now in the car is in good condition, so that's why I have no rush with this one. When I bought the car, I thought that I will drive it about 4-5years and trade to 997. But now that I have drove with it about 10k miles in 8 months, I think that I will keep this. Plans are to paint the car riviera blue and build more powerful engine for it.

Honestly though, it sounds like you want another car. Not to rain on your plans or anything like that, but whenever I find myself thinking "if only it had X and Y was different and the engine was a Z" I can fairly quickly tell myself that I'm on the wrong track and need to change cars. This goes for expensive things like new engines and colorchanges. Minorish mods are fine. Just my 2 cents and all that.

pretty sure the bolts "fit" but with the entire vario cam set up completely different, the cam held in place different, the scavenger pumps different, the chains, the lifters, the cradle, the cams and possible some other stuff I think the effort would be enormous - but I really dont know that...J.R. is the expert, call him

If you want more power and can't go with a turbo I think a larger bore (example: http://www.lnengineering.com/boxster.html ) or super charger (example: http://www.vf-engineering.com/kit_porsche_996.php ) are going to be your best bets. Of course the money you might spend on the above you might be better off selling your car and spending it towards a down payment on a turbo?

Also I would think the gains you would find from the 3.6 over the 3.4 are going to be from displacement... not the top end... (although the variocam plus system certainly adds some spank over the standard 3.4 variocam system - that's just one of the hurdles in trying to make a mutant).

logray, looking to keep the low end torque, and get better top end power. The supercharger has the same problems when tryingh to get the car thru inspection. I have built several engines before, 200 to 700 hp. NA and turbo So thats no problem for me to build this one. Nyegaard, in any other country, you would be rigth We have this nice car tax system. 996.2 cars costs around 50k eur.... thats 70k usd... So now the plan of using 10k eur to 30k car seems better idea? Allso after the build, I know what the car is Allso, I can sell the old engine after the new is ready. That will lower the total costs nicely. Ivangene, thanks I did not remember the scavenge pumps. I think that the head gasgets are the same, so the oil passings for scavengepumps might be the same. And making the adapter parts for chainsprockets is no problem. And thank you for replys, I need to find out all the options and prices for those first

Check my 3.2- 3.6 build underway thread in this forum

For the 10k euros personally I would look at the 3.4L to 3.6L big bore conversion from a company such as LN engineering. Not only do you get more displacement, but you will bulletproof the cylinder block as well. I've read a few posts where this upgrade, along with freshening up of components is worth 50-60hp over stock. So half way to your goal of 100 hp... perhaps if there is money left over camshafts and other bolt on's or ECU tuning could make up the difference?

Thanks Byprodriver, I havent seen your 3,2 build before. I think that thats the best way to proceed. If I may ask, how much did you spend on parts? And did you get the blocks ready or did some machinist do the fitting for the sleeves? logray, budget allso includes the paint job. So the engine should cost about 5 to 6k. But the engine is the first priority, becouse the arctic silver that is on my car now is in good condition. Plan is to build this engine next summer, so there is lots of time to figure out what to do Or, I might get some banger for the winter and rebuild my old engine... desicions desicions...

Speed rII, look at the link I sent to you earlier.... it describes the whole process. It's the same thing byprodriver did. $4100 US dollars if you ship to them your cylinder block. They send you the upgraded block back along with new pistons. Here's the link again... http://www.lnengineering.com/boxster.html

There's also silsleeve by Autofarm in the UK. http://www.autofarm.co.uk/engines/water_cooled/pricing 3.4 to 3.7L upgrade for 3000 euro plus another 1000 for 3.7 L pistons.

Thank you, logray. I somehow missed the links from you previous post. 3,7l tempting...

I'm dying to come up for a reason to do it on my car...

That is stage 7 for my car. My mechanic quoted it as: Full Motor build 3.4L to 3.6L, JE pistons, R/R connecting rods, Crankshaft, Ported/Polished Heads, balanced rotating assembly, custom tuning for dme. I believe rwhp was 316 or 330.

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Ok, that would take the hp level right were I would like it to be. So, now that the solution is found, I have to make the funds for it I think that I will contact the autofarm and ask for the sleeves and pistons only. I have couple of places that let me use their milling machines... Thank you everyone

I'm resurrecting this old thread in hopes that I can find some more info on putting 3.4 heads on a 3.6 block. Does anyone know what needs to be changed (specifically) to do this? I am not interested in other engine configurations. I am specifically interested in the changes required to put a 3.4 VC1 head on a 3.6 block. I will be retaining my wiring harness and cable throttle.

I never went thru this, and still running with 3,4l. If my memory serves me right, you can get the 3,6 from 3,4 just by changing the crank and rods from 3,6l to 3,4 block. Allso your IMS tube must be the one with newer chain from crank to ims. I believe that JrGordonsenior has this setup in his racecar??

Anyone know if the guide pin locations for the chain rails in the head are the same ? Combustion chambers of the 3.4 and 3.6 heads are different. So I wonder if the over bore vendors (LNE etc) have different piston designs to compensate.

Here is what I think. The boxter S 3.2, 911 3.4 and 911 3.6 engine case halves are pretty much all the same. The 3.2 engine has a smaller bore than the 3.4 and 3.6. Heads on the 3.2 and 3.4 appear to be identical. 3.6 heads are VarioCam+ yes Porsche could have varied the chamber size over a few years to mess with the compression ratio. You could look at the specs for the different engines to get the compression ratios for each MY. I think you could deck a pair of 3.4 heads to increase compression ratio but may run into problems with the limits of the camshaft chain tensioners. There is also a stroke difference between 3.4 and 3.6. The bearing cradle, IMS shaft, crank, and rods could conceviably be transplanted into a 3.2, 3.4 or 3.6 case to increase stroke. of course if you sent your stuff to LN engineering and got the 99mm bore increase with a 3.6 cradle/crank/rods in a 3.4 case with 3.4 heads you would have a 3.8 engine. I do know that from researching this that some of the oil passages on the bearing carrier assembly are different on the 3.6 than the 3.4. I am not sure if this was just a upgraded design change to account for better flow within the bearing cradle or if it would have some adverse effect. I plan on contacting Porsche to ask. I think that VC+ is a cool concept but it is way too much trouble to change the computer system to get it all to work ....key word.. correctly. Just give me more displacement and I will be happy. I know there is someone on here who went with the thicker walled 3.2 boxter case and 3.6 bearing carrier to net 3.4 (bulletproof). I wonder if they could chime in here. research the Porsche parts catalog and look at what parts are used on what years... its not always all inclusive and i think some modding might have to be done to get this to work with that... but all seems to be doable.

Thanks Amille28, I've heard a few have done exactly that. Drop the large stroke carrier into an earlier case. I'm curious about the details surrounding the pistons & combustion chambers. Sure it may work just bolting those parts together, but I'm looking for maximum power so valve clearance (high lift cams) and piston crown to combustion chamber shape matching are of concern. I have yet to find real details on what guys have done with the pistons in a 3.6 case with 3.4 heads or in an LNE type of 99mm bore (JE) 3.4 to 3.6L configuration. Do guys buy the JEs for 3.6L to get the correct pin height and then compromise on the chamber shape? or ... I've tossed a few pics in here to show those who may not be familiar with the differences between the 3.4L and 3.6L cylinder head combustion chambers. The first (left) shows a dirty 3.4L type chamber. The second a side by side of the 3.4L and 3.6L. The 3.4L has obviously had a skim cut to clean things up and custom stainless valves. I'm going through the analysis phase of a project, comparing 3.4L, 3.6L and GT3 parts. Interesting to see what the similarities are. I agree with you that the VarioCam+ isn't worth the trouble. I'll take the '99 electronics with actual cable throttle and easier to tune DME. The 3.6L valves look badly shrouded in the head. Plus the more "normal" 3.4L cams are cheaper to have ground. I also agree that displacement is the way to go. I originally wanted to keep the short stroke (78mm) of the 3.4L to get something that revs more like a GT3 (76.4mm). However after thinking about it I don't think the other engine parameters are suited to make more power up high.

We create these types of "mutants" frequently. It can be done and can have benefits, but there are things to overcome that are quite challenging. The biggest difference is the timing chains, which require case splitting to swap out. A big consideration are the valve reliefs in the pistons. You won't really know what you have to overcome until it runs for the first time. I worked through this years ago with zero assistance and it wasn't fun.

Jake is right and is the specialist on the topic. It looks like the chamber (quench) area of the 3.4 head is smaller than the 3.6. That combined with the increased stroke of the 3.6 bearing carrier assembly could and probably does lead to valve/piston clearance issues. It could be done but you would have to really research the clearances. Additionally the x51 package from porsche changes the duration and lift of the camshaft. This was a package with aluminum intakes, heads, upgraded ims. Do a search as someone posted dyno sheets with stock then stock X51. I think this franken-engine combined with a cam regrind closely watching valve lift could get you to the 360hp goal. How cool would it be to turn your 3.4 into a poor man's cup car. Downside is that the X51 was a really expensive mod and not even sold in the 3.4 version in the US. You might even be able to get a lopey cam duration that would have made Dr. Porsche throw up in his mouth a little hearing it.

Agree on the quench area comment. That's why I was asking what people have done with the piston top design. Anyone know the pin heights on the 3.4L vs 3.6L pistons? If I recall the 3.6L rods are ~3mm shorter. >> You won't really know what you have to overcome until it runs for the first time. If one were just throwing parts together I'd agree. I'm familiar with the X-51 and will not be using those components except for maybe the int & exh manifolds. There are no X-51 cams for the 3.4L US spec heads. I need to get the heads cleaned up and cc the chambers. I'll post the #s when I get to that stage. Measured the included valve angle last night. 28� just like the GT3. Bodes well for using GT3 porting data as a guide. But we'll cross that bridge when we come to it.

Check this out, good thing im kinda fluent in German. I found the OEM company that makes the camshafts and found the pdf link to their catalog. Here is all of the different durations, lifts, and even prices of the cams.... Anyways Ventilhub is the German word for lift.. you can see that there are several different cam profiles for the 3.4 engine. Looks like stock lift was 10.7mm. The words "verstellbarem Kettenrad" mean adjustible chain wheel and so it has a range on the duration. I am thinking this means the range at which the chain tensioner can vary duration. Stock 3.6 lift looks like either 11.5mm or 12.0mm the link http://www.avl-schrick.com/dat/MK/Sc...202009%20D.pdf best translator english-german dict.leo.org I'm still looking for the piston info.. seems they are made by Mahle OEM but they arent listed on their website.

What you're looking at is their motorsport catalog. And while it's fun to read it in the mother tongue (ein bisschen) you can also get a copy of the English version: http://www.avl-schrick.com/dat/MK/Sc...202011%20E.pdf Yes the pistons are Mahle. And yes the cam specs are given for "large stroke" and "small stroke" or the delta between full advance and initial timing advance. Stock lift on the 3.6L is not 12mm as that's a high lift race cam. 3.6L is either 10.7 or 11 at most. I dont have that spec with me atm. For kicks, here are the X-51 cam specs for the 3.6L X51 Cam Specs ATDC/ABDC/BBDC/BTDC Large Stroke IO, IC, EO, EC 9�/61�/50�/4� Small Stroke IO, IC, EO, EC 39�/19�/50�/4� Or 9�-39�/61�-19�/50�/4� I have been looking at Schrick, DeBilas, and FVD cam specs.

Can anyone point me to a part# of the Harmonic Dampener Porsche uses on the 997s ? Anyone making a smaller dia. or lighter harmonic dampener? I see RSS makes one but it says: Fits 997 mk1 3.8L Models Only. Need to inquire about that.

have you gotten anywhere with this. Did you ever find the piston dimensions you were looking for? Will the 3.4 vc1 head bolt on a 3.6 engine?

The 3 chain head will fit a 5 chain engine with two modifications.

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Oh heck yah... bolts right on. I spent all last winter tinkering and now I have a new large block motor with my old 3.4L heads in the car. Will be doing a set of ported heads with Ferrea valves and Schricks this winter. Here are some build pics: http://www.flickr.com/photos/apex944...7633702078228/

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Sweet build pics! That is a seriously clean workshop. Thanks for sharing. Cheers, TomF

Apex, You say it bolts right on.. are there any gotchas? Or are you being sarcastic. Its hard to tell over the internet. My engine died about a week ago and I'm working some different options. Thanks for your time. I know it seems like a stupid question.

Two holes must be drilled and tapped to facilitate this swap, and the proper head gasket will only be compatible with an altered bore size.

Did you keep the original 3.6 pistons with the heads swap?