hotrodf1

Hey all,
I've read and read about clutch / flywheel balance issues, but I'm coming up short on answers.

I have an LT1 in a third gen camaro with a T56 behind it. The flywheel appears to be a factory piece. It does have 1 of the holes in the perimeter of the flywheel plugged with a pin. Supposedly you need to move this pin when installing a new flywheel.

Anyhow, I have a fairly bad vibration that I need to fix. After reading about the cheap China pressure plates that aren't balance, I figured that was my problem. A previous owner had put in one of these kits. However, the vibration is still there, even after removing the clutch and pressure plate, and reinstalling the Trans again, along with crossmember and exhaust. So it would appear something is off with the factory flywheel??

I took the trans back out and pulled the flywheel only to find that there was a bunch of crud built up inside the flywheel itself. I have since cleaned all that out and reinstalled but have yet to re fire the car with the tranny back in to see if it made a difference. The crud I scraped out didn't weigh much so I kinda doubt it's going to be the fix.

I have looked at the front balancer while it runs - and it doesn't feel like the vibration is nearly as bad at the front of the motor. Oh, initially, I ran the motor with the oil pan supported by a tranny jack (trans was out of the car) and I guess with the motor sitting on the trans jack the vibration was sent to the ground because I couldn't feel the vibrations in the car at all. So after that, I decided I needed to check for vibration with the trans in the car and crossmember supporting it like it would be.

So with the clutch and PP off, the motor "should" be smooth correct?


If I thought a new flywheel would fix it, I would spend the $70 at rockauto and move on. Kinda hate to throw money at it, especially since I think it's the original flywheel (which I gather should be vibration free). Why would it be far enough off to create this vibration?


As far as the weight "pins" in the outside of the flywheel - is there any way to determine how many / what position these should actually be in? Were these pins used to fine tune the balance of the flywheel / clutch PP during assembly ?


I should note that I have new trans and motor mounts - stock rubber style. Using the Hawks swap crossmember. Do have LTs, but I have checked for clearance they aren't hitting anything.


Vibration seems to be there whether in gear and going down the road and same now with car on jackstands in the garage and clutch and PP removed.


Any thoughts out there would be much appreciated.

Tuned Performance

iTrader: (92)

https://www.thirdgen.org/forums/tran...ion-after.html

Have you read this thread ?

jmd

iTrader: (4)

Yeah. When you get it apart, do you have a stock 91 flywheel or flex plate to throw on to try out?

The pin is a problem. Because, the Valeo pressure plates were aligned by the bolts. The stock bolts indexed to countersunk bolt holes in the flywheel. You need to make sure your bolts are threading in so the smooth section above the thread sits in the countersink bore in the flywheel. If you have "what we had in the bayou" parts, the PP may not be aligned.

jmd

iTrader: (4)

About the dual mass flywheel he doesn't have?
The tech there is excellent, for intended purpose. The flywheel in discussion there has a dynamic balance potential. The LT1 T56 flywheel is static, and should suit any 86-03 production gen I or II SBC.If it doesn't, it needs rebalanced or replaced.

hotrodf1

But the pressure plate is out of the equation. It's not even on the car at this point, trying to rule out what's going on by getting it smooth with just the flywheel. Then I will add the clutch and go from there.

I cleaned the flywheel up well and tried it again and same vibration amount.

So I tried another flywheel from my racecar (quartermaster twin disc), that I know ran smooth on my other motor (non LT1). Ended up with the same vibration as well.

So then I got crazy and tried a flexplate from a neutral balance motor and found the vibration greatly increased. Didn't run it long that way. Obviously not the right direction.

THe only thing I can think of is somewhere along the line some jackwagon put a non LT1 crank in it that was balanced for heavier pistons or something. I didn't pay attention to the casting number when I put it back together. Didn't think I needed to.

Next step pull the crank and have a shop balance the flywheel and crank?

five7kid

iTrader: (14)

Have you checked the damper?

hotrodf1

Dumb question but how would I check it? While running I don't see anything obvious. Can I just pull it temporarily and see if the vibration is better or the same??

five7kid

iTrader: (14)

Check for damage or wobble is what I was thinking. I suppose you could run the engine without it for a short time and low RPMs - never tried it, personally. Or heard of it being done.

hotrodf1

Yeah I gave it a look from under the car while it was running and didn't see anything odd. When I had the motor apart I didn't notice any rubber out of place and whatnot. Didn't know if it could somehow be out of balance. Guess I'll pop it off and try again. And here I was so proficient at tranny removal and install. Now I'm gonna have to learn a new skill lol.

I hate the thought of pulling this apart to balance it.

hotrodf1

alright finally read this. Actually quite interesting. Seems like perhaps I might be able to help my situation by adding weights in different spots. At least it can be done with the trans and all in the car. So would be fairly quick to try and determine where and how many pins to add. Should at least be able to make it better I would think. Trial and error process but it's "free"

Thanks for that link. Anyone know what size those pins are???

hotrodf1

Update:
using 1/4" rod stock sanded a bit to ease install I have been playing with the balance. Seemed that I need weight to offset the counterweight. I had 5 1 1/4" long pins directly opposite the counterweight. That helped a good bit but still not enough. Thinking I was going in the right direction the only next step was to lighten the counter weight

i did this by drilling the counterweight from under the car with a 7/16" drill right next to the oil filter. I have ended up putting 7 lightening areas and am getting very close to " good enough". I can finally rev it to 6300 without it feeling like it's going to tear itself apart. Strangely enough, I gotta be close to neutral balance b now but when I tried that it was way off.

Only took all day but it's going to be worth it.

I beleive others out there with a similar balance problem could find a nice balance using this method. It's tedious and a bit hard to determine "Better or worse " sometimes after a change. I ended up moving about 3 of the pins around to see what would make a Change for the better. Then just keep going in that direction.

Every so often I would go back to a known "good" combo to be able to compare. If there was a way to measure the amplitude of the vibration that would really help.