Engine Builder Help!!

Background- 1999 C4. I noticed metal during an oil change and discovered the IMS had started to come apart. Decided to do a complete tear down and re-sleeve with Nickies. I got the block back together and while checking the deck clearance I found the #1 piston sits uneven fore and aft (along the axis of the wrist pin) -.008� aft vs. -.016� fore. Also, the #1 and #6 cylinders have minimal deck clearance, -.001� at 12 o�clock while applying pressure at 6 o�clock. All other cylinders measuring -.008� or -.011� All measurements were taken with only the case bolts in place. Nothing else holding the bearing carrier. Is this normal, am I doing it wrong or did i screw something up? Thanks!!!

I rebuilt mine as well but I am not a builder so this is just my opinion. You are measuring thousandths of an inch. I'm not sure you can do a deck measurement on this engine with out having your headbolts torqued. You are so far down the path anyway, why not secure everything and then do your verification?

Thanks Daniel! I don�t disagree... but spending the last few months lurking around the forums has me a little nervous, to say the least, that I�m going to muck something up. I have been considering that things may not be perfectly aligned until the heads are installed, but I�m not sure how I�d check the deck clearance after they�re on. Thoughts??

are you re-using the same pistons? if so back in the same cylinders?

No, using the pistons supplied with the Re-sleeve.

The head bolt attach to the crank carrier. I expect that not having the head bolts torqued yet could make some minor differences.

Thanks... that seems logical in my mind. Maybe I�ll put the bank 2 head on and see what that does on the bank 1 side. can I entice Mr. Raby to chime in? I get to GA for work a good bit, i�d be happy to bring by some bourbon and cigars. 😁

Unfortunately he has left the forum. Last weekend he was on a beach relaxing.

Good for him, bad for me!

Call or email Charles @ LN Engineering (did you get the Nickies & Pistons/rods from him?) I'm sure he can get you sorted...

I did not get the connecting rods from LN (reusing the originals) but pistons and sleeve did come from them. I didn�t reach out to Charles, but was in communication with one of the employees. In short, he feels the deck clearance is fine but stated �we offer no assembly guidance. For further assistance in building, contact flat 6...� and would not entertain a call to discuss the issues I�m seeing. On one hand I understand. They recommend using a reputable builder and are only responsible for the work they do. I�m a little put out that the 6k I spent with them doesn�t give me a quick call, not to seek assembly guidance. I have the manuals and I�ve watched the videos. I know how it goes together... I would however, expect some guidance on what the issue could be. It�s unlikely, but the piston itself could be the culprit. But I digress... Heres my plan: I�m going to crack the case. remove the #1 & #2 pistons Swap cylinders, #1 to #2 position see if the problem follows if it does, I�ll swap connecting rods to see if it�s the piston or the rod. that�s the only thing I can imagine it would be. Maybe the rod got bent when fitting the new bushing... I�ve come to terms with the fact I get to build it again... it�s a learning process... I�ll post pictures and progress reports just in case someone has a similar issue in the future.

As a follow on to my last post. I did reach out to flat 6. I�ll leave names out to protect the innocent but spoke with a very nice man who offered some direction and most importantly, encouragement!! It can all be fixed and soon enough, I�ll be back on the curvy mountain roads!

LN Engineering Tech 139 here. Yes, Mr. Raby ended his RL support a few months ago and has no plans to return. He was on the beach a week ago, he is now somewhere on his 120 acre sanctuary trying to recuperate from Rocky Mtn Spotted Fever after being bitten by an infected tick in one of his outdoor escapades. His time is valuable, and he always charges as necessary for assistance in situations like this. We spoke to Jud at FSI this morning and he said that he gave you some good pointers, and informed you of the FSI technical fee. As LN Engineering's Advanced Technical Director, I seldom have interaction with purchasers, but I felt like this scenario demanded some of my time. I reviewed all the specs for the block deck heights and other measurements. Since there's some question marks I think these should be explored. First off, the factory connecting rods were never designed to be remanufactured. Usually the big and small end of these measure perfectly and upgraded LN/ ARP connecting rod bolts are all they need. Should they be altered, the chances of them being improperly sized, or sized incorrectly is great. The small end bushings in these rods do not wear- at all. FSI has barrels full of these rods that you could buy a matched set for a very good price, which would be a great corrective action moving forward. They very seldom use them, as they use the proprietary CP rods and LN rods that we manufacture for them. At .008" I'd question of the rod is bent, which can happen. I would strongly encourage that you invest in the Raby step by step 15 hour engine build DVD, since content about checking your work is there, and crucial. I think at worst you'll need a new set of rods, which is a cheap way out. When you hit a problem like this, just be glad. You found it before it found you, which is the outlook I was taught when being trained by the team at FSI. Let us know what you find :-) Tech 139 ATD- LN Engineering

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Love this kind and well thought out guidance. If only I had the shop and training to rebuild my own M96. Alas, I will have to use FSI or another approved when / if the time comes. It's just good to know, great to know, that there's so much expertise around the 996 series, and so many good options for upgrading, or, for me most importantly, maintaining what is essentially my dream car. I have loved the 911 since I first discovered them, I think it would have been maybe 1976 or so when I started falling in love with motorsport and Porsche. That makes sense, I was 12 or so, and my parents owned a bookstore, an independent book and magazine and LP records shop. That's where I found Road and Track magazine. And where I read the first review of the Porsche Turbo. When my dad had a heart attack, his surgeon drove a dark brown 930 turbo. I was taken for a ride in it, and never forgot that. Now I have my own 911. And you can have it when you can pry it from my cold dead hands..

@Mdelay I stand corrected. FSI just sent 6,000 pounds of stock M9X connecting rods to the scrap yard a couple of weeks ago. I was unaware of this until Jud just rang us to give us the information. With their new program only utilizing billet rods, I guess they wanted to get them out of the way. I apologize

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Thank you!! I really appreciate you taking the time to respond. This is exactly what I was looking for, someone with a solid background on these engines saying, �You might have a bent rod, maybe look at that.� Or what I was hoping to hear, �that�s totally normal, slap it together and get driving.� (A boy can dream can�t he?) Sorry to hear about Mr. Raby. Get well soon! I do want to clarify one thing, I wasn�t really asking or expecting Jake to chime in, although had he, I would have made good on my offer of bourbon and cigars! 😁 The big question now is, $499 for a used set of rods on eBay or k1 rods for $1122??? It�s only money, right?

I think I still have a couple of stock 3.4 rods if you want them.

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PM sent.

Here’s what I have: 996.103.975.01

I’ll take it! Thank you!!

I have some 3.4l rods too but my motor went boom. I figure 3 or 4 r probaly good. Lmk if u need more.

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thanks!!! I�ll let you know. I should have time this week to open it back up. I should only need one but you never know. Im also still considering the forged rods from LN. I go back and forth as to what�s necessary.

Be aware that factory rods are only sold in sets of 6. They are grouped in weight to a degree of 3 grams. I have seen rods from different engines be a much as 15 grams difference, and there is not a good place to remove that much material, so weight matching/balancing is impossible. So if you are trying to match your existing rods weight, you may need quite a few to find ONE that is close enough to match. Same as with factory pistons, they are grouped in groups of 3 grams delta. Most good race shops will weight match/balance to within .5 grams.( But remember, this is not always possible IF the original casting is too far off.)

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If you go that route, we finally got in more Carrillo rods (they are made to our spec, not the spec of the shelf M6 rods) but we will not have the more budget friendly K1 rods in until Sept due to supply chain delays.

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And just like that, more wind out of my sails. Haha.

I had time today to disassemble. The good news is the rod doesn�t appear to be bent. It looks like the bushing was not installed correctly at the machine shop. So I should be able to get another bushing and have it installed, maybe correctly this time. I�d made up my mind to just spend the money and get a set of the K1 rods until I saw Mr. Navarro�s message. I think spending another 2k on connecting rods may be over kill for my application. I�ll never track this car and it�s a cab so I don�t even drive that fast. Lol I�m open to suggestions. Sits pretty flat.

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Thanks for that info! I weighed everything thinking I�d need to make adjustments, I had One rod that was off by 1g. I was stunned at how well everything was matched.

When LN says that the small end was not engineered to be remanufactured, I would listen (in my opinion). I have a full set of 3.6 rods from my rebuild (I went with K1) but I believe they are different spec that the 3.4. If not, you can have them. You have concerns with an installed bushing already. My vote is buy new rods. But that's just my opinion.

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You can change the pin end bushings out, but the replacements from Porsche are questionable. If the rods are in spec, changing out the rod bolts for ARPs is certainly doable, but we do recommend replacing the stock rods when going to the 101mm bore size, especially if you plan on doing any performance driving events such as an autocross or HPDE.

There's a lot of consistent events on here not to trust the factory rod bolts as LN have advised. Having done so much I don't think you can have too much rod strength. Small displacement high power compared to a Chevy V8 most mean high forces on the reciprocating assembly.

Thanks to everyone! I�ve decided to get the Carrillo rods from LN. Just seems to be the best, easiest and quickest solution. At the end of the day I don�t want to feel like I�m driving a grenade every time I take her out. buy the best and only cry once!

Walking the talk to you, I ordered Carillo from LN with their 101mm Nickies sleeves, giving me the 3.4 to 3.8 in M96. I was never pressured to go Carillo over K1, but don't believe you can over engineer. A balanced built bottom end is not just insurance it feels better if you are mechanically sensitive (everone else will tell you placebo). I went with billet Oliver I beam rods in my modified LS9 (in Holden Senator - Aussie high trim Chevy SS), in collaboration with a Nationals winning builder. Given your efforts you won't regret quality parts.