Hey guys. So I pulled my old flywheel, marked orientation, marked bolts, marked everything so I can put it back together the same way it came off. Now, I took the old flywheel and the new flywheel to a machine shop to get match balanced. Now, I wasn't sure what they needed so I brought them everything (Old and new pressure plate, clutch disk, and flywheel).

They tell me that they matched the new flywheel to the old one, and then they bolted up the pressure plate to the flywheel, and zero balanced the assembly out. Now, I'm not sure if this is right so I've been looking into things a little deeper. He told me that the flywheel can only go on one way, and that theres not 6 possible ways to bolt it up. Measuring the bolt holes, they all are equal distances apart. Theres like an alignment hole but I don't believe theres an alignment pin on the cam? If this was the case, it wouldnt have been a big deal as to markinf where the flywbeel came off of right? Then he said if it could be bolted up in 6 different positions, it wouldnt matter because the assembly is zeroed out. I was under the impression that it did matter. I really need to speak to someone who knows these motors well. I dont want to reinstall everything and have it be wrong. Thanks.

 

there's a crater machined out of the crank that will match up with the hole on the flywheel but there is no alignment dowel so you could install it in any orientation... just reinstall it with the holes matching up to be safe but if you had it all zero balanced you should be fine

 

I'm going to make my best effort to not sound like a jerk. But, I literally answered every one of these questions in your previous thread:
https://www.corvetteforum.com/forums...s7-clutch.html

An attempt at nice answers are above in BLUE

You don't have to take my word for it. If you really want to know about any of this, you can research it yourself, contact the GM engineers that worked on the C5 and C6 platforms, personnel that actually performed and still perform the hot balance at GM, the past lead NVH engineer at Milford proving grounds, and past and current corvette powertrain Engineering supervisors. That's who I talked with at length during my research. I don't know who would know "these engines" and this issue any better.

I sincerely hope your situation turns out well. It is such a pain to chase down vibrations. Where you are at right now, I would just install it as is and see what happens. Cross you fingers and hope for the best. There's a good chance it will be fine or at least something you can live with. I just hate that you probably got charged for a completely useless procedure at the machine shop.

 

Ok, so I spoke to the machine shop and he said that he matched the flywheel to the old one. He didn't balance the old assembly, he just balanced the old flywheel and then zero'd my new flywheel, and then matched it to the old. After that, he then zero'd the pressure plate out by itself. He spun the pressure plate by itself for grins and saw it wasn't zero'd perfectly so he zero'd it. After that he installed the new pressure plate to the new flywheel to confirm that the new flywheel was still the same amount "off" and he made sure it was. I do appreciate your help here and I know I've been asking many repeat questions, mainly as confirmation. Sometimes, text can be read wrong or interpreted wrong, etc. Regardless, I appreciate your help very much so and I certainly hope that this guy knows what he's doing. He's a well known engine builder in this area and I may just be relaying bad info, I'm just relaying info as I understand from what was told to me. He has 4 lamborghini motors, just did some maserati head work, did nascar for quite a while, etc. Hopefully he did it correctly and I'm just dumb and don't quite understand exactly what he did.

 

I don't think you are dumb. This is a unique issue to corvettes with manual transmissions. It has nothing to do with engines per se. This dude could be the best dang engine builder in the world, it's irrelevant to this issue. You care enough to take the time to attempt to get something matched, and that's a lot more than a lot of people do, so you're not "dumb". It's just frustrating when several things I warned about when dealing with the shop doing the balancing comes true, even after I try to spell it out step for step. Even spelling out what the shop will end up trying to do.

OK, so what you are saying now, in a nutshell, is that you now have a FW/PP combo that matches the balance of you original FW alone. Does that make sense to you? Your new combo now matches what you original flywheel did alone by itself. If your original pressure plate was zero by ITSELF, this is then a perfect situation. However, I am sure, from what you said and what they did, that they DID NOT put the original pressure plate on the machine and see what state of balance it had alone. Just to give you some perspective, the pressure plates were delivered with a balance tolerance 3 times larger than the flywheels, so chances are it is not zero by itself to the degree "required" from the hot balance.

Do you have a good relationship with this shop? Are they close enough to you that it's not a pain to get to them? Would they be willing to see what the balance of the original pressure plate is by ITSELF. They haven't touched that so it will be whatever it was from the beginning. If you do that and it is already pretty close to zero then you are good. If they are really nice, maybe they would even bolt up the original flywheel and pressure plate together and see what that balance is. That's what I advocated from the beginning. THAT'S what needs to be matched. It is encouraging that you said they bolted up the new assembly together and checked balance. That means they KNOW how to do that! You'd be surprised how may shops won't even do that. So this is all great. If you are willing to go one more time, have them check the balance of the original FW/PP assembly against the balance of the new FW/PP assembly. The new assembly currently matches the balance of just your original FW.

If they want to know WHY you are asking about this, explain it this way:
When GM does this final fine tune balancing, they mount BOTH the flywheel and the pressure plate to the engine. The engine is mounted in a balancing stand machine, outfitted with several accelerometers. They then run the engine on natural gas. YES, NATURAL GAS. How about that??!! The machine reads any imbalances and tells the operator where to install balance weights, and how many, in either the flywheel, the front damper, or both. They do this until the final total balance is within 0.5 oz-in. The engine has its own slight imbalances, the flywheel has its own slight imbalances (due to tolerances), and the pressure plate has its own slight imbalances (due to tolerances). Put them all together, you get stackups. During the balance process, when they install any weights in the flywheel, they are accounting for total imbalances from ALL the components. Not just the flywheel alone. That's why you don't just match the flywheel. You end up with a unique FW/PP combo that now goes with you own unique engine to create an entire assembly that is below that final balance tolerance.

Or, as stated before, you could install it as you currently have it. There is a good chance it will be fine. IF you have vibrations afterwards, at least you still have your stock stuff to go measure their total assembly balance, if it comes to that.

Did you or the shop look to see if you had weights in your original flywheel? Did they tell you or give you a readout of how much it was "off" from zero?

Also as previously stated, now several times, GOOD LUCK to you Sir!!
I mean that. I wouldn't take the time to write all this if I didn't care.

here is a cool article, build for LS9 engine. Same final balance procedure.

https://jalopnik.com/5371569/how-we-...-corvette-zr1/

Check out the build steps, and near the end is this :
"Since it was a shutdown week, we didn't proceed to the next step, but normally the engine would go to the balancing chamber. In the balancing chamber, the engine is hooked up to an isolation fixture which freely allows multi-axis vibration. It's then hooked up to a special ECM and a natual gas fuel source and fired. That's right, a Corvette ZR1 motors first breaths come from a clean fuel. During the engine's operation, sensors detect vibrations and calculate where to add weights on either the flywheel or the crankshaft damper to bring the engine into balance. The weights are installed and the process is repeated until it passes the test. The final step in the process is a second, intense inspection, from the assumed position of the customer at the Bowling Green Corvette factory. After it's gone over with a fine toothed comb it's off to storage awaiting the truck to Kentucky."

another cool video, build form the factory. Mentions the post build balance process just after time stamp 8:52. Notice how they say going in to cars with manual transmissions.

 

Interesting. I must have missed where you previously stated that the pressure plate and flywheel are balanced together. I was under the assumption that it was just the flywheel that gets balanced, and since the pressure plate is "zero'd" from factory, it didn't matter as long as the new flywheel is match balanced to the old flywheel. I did not realize that its the flywheel and pressure plate that matters. Unfortunately, that machine shop is two hours away and in the bay area. Trying to get there at all today would be nearly impossible, and I need the car running and driving by tomorrow night. So unfortunately it looks like I'll be taking a gamble and just using this new assembly. Let's hope it works. I trust he knows what he's doing and I'm just relaying wrong info. Lets hope for the best! Again, thank you for all your help and I do appreciate holding my hand through this. This is why I love this forum!

 

There's no sense worrying about what you can't control. You have what you have. Just install it as is and see how it goes. Chances are it will all be fine. If it is not, there are fairly painless ways to fix it, and maybe even without taking it all apart again. That would be nice. I can't stress this part enough. PLEASE PLEASE PLEASE DO NOT throw your original flywheel and pressure plate away! They will be your biggest aid in fixing it IF you have a vibration problem.

I'll ask again, did you or the shop look to see if you had any weights in your stock flywheel? Were there any? How many?