The vibration caused by an unbalanced flywheel can be pretty significant. That's a good place to start. Frankly speaking, I'd just go out and get a stock replacement iron flywheel...aluminum is a pain in the bleep to drive.

The markings on the crank probably refer to the undersize dimensions on the cranks main and rod journals. 020/020 Vs 010/010 doesn't make a difference if the bearings are clearanced properly. If the weren't you'd get knocking noises, not a significant vibration.

My opinion is that throwing this engine away is a costly mistake. The issue is likely minor, especially since it started with a major maintenance event.

As I sit here and think about it, take a look at the exhaust. If it's touching anywhere except the mounts it can be a source of vibration. SInce the tranny was just out, who knows what could be going on down there....

Good Luck...

 

So drop the trans. take the clutch/pressure plate off. Start the engine, if the vibration is gone, it's the clutch!!! You don't have to spend any money yet.

 

NOW, you tell us. There have been threads about some replacement clutches not having the balance correct. There is also some balance markings that should be paid attention to when a clutch and flywheel is installed.

Had you spent all that money on a new engine and then put the same offending clutch on it, you would not have been very happy.

 

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The exhaust mounts are not touching, that much i can confirm. The vibration im talking about isnt loud pitched, its more of a groan/vibration in conjunction with eachother on acceleration (to be more specific)

and i can confirm that it does not do this with the clutch pressed in, only when its under a load, and its noticeable in every gear.

I was extremely frustrated with this car yesterday, thanks again to everyone for helping me pinpoint this problem i was ready to tear the thing to pieces yesterday.

now that ive got my head on straight, and elaborated further, could it still be the clutch/flywheel setup?

 

yes id have been very unhappy. Part of me still wants to replace it, just because of the fact that a new engine means, i know everything thats been done too it, granted this one is very obviously rebuilt.

 

think i would pull the trans, clutch and flywheel.. take the flywheel and clutch assembly to your local automotive machine shop and have them check the balance again..
if you have the stock flywheel take it with you to show the machine shop, that way they know the imbalance/counter balance of the flywheel..

make sure they are aware of the lt1 is not neutral balanced..

while you do that, check the pilot bearing and make sure its the correct size and check the input shaft on the transmission and make sure its correct size and also that it isnt loose..

 

im not sure what this means, LT1s are not neutrally balanced stock?

 

The LT1 uses the flywheel as part of the balance of the crankshaft. The stock flywheel will have weights on it to act as a counterbalance for the crank.

Did you replace the flywheel with the clutch or wasn't the flywheel touched when the clutch was replaced?

 

they are not neutral balanced... lt1 in stock configuration have a counter weighted flywheel/flexplate...

 

the flywheel was replaced originally with a stock clutch replacement (at the same time)
later down the road (when i did all the upgrades) i went with a barnetts racing stage 1.
keeping the old flywheel, the flywheel i ordered at the time, i thought was stock, but according to my mechanic, its aluminum and its from mexico. the vin numbers are for my car, but im starting to think the flywheel is not correctly balanced,

but why would the groaning/vibration show up AFTER i replace the clutch but dont touch the flywheel?

maybe i should just go with a completely stock flywheel and see what happens from there.?

 

ttt

 

VIN numbers are for your car? I'm confused with this statement.

Were the "new" flywheels balanced to match your stock one that was replaced?

Whatever the issue is, it sounds like it's something with the Clutch, maybe the disk threw a chunk of friction material, maybe the disk is in backwards, maybe a bad TB bearing, Maybe a bad Pilot Bearing. Whatever it is, it's something with the clutch.

 

All stock motors from '86+ with a one-piece rear main seal are internally balanced on the front and external on the rear. I would run away from any shop that doesn't already know that without you needing to tell them.

 

Bottom end 355 4-bolt main.

http://high-performance-engines.com/...duct_Code=SP34

http://high-performance-engines.com/index.shtml

 

Check to see if you have holes drilled in the sides of the pressure plate. This is how they balance it. If you don't have any, there is a good chance that your pressure plate is unbalanced and causing your vibration problems.

Read this...
https://www.camaroz28.com/forums/sho...d.php?t=663827

It documents my problems with the Autozone clutch kit. It also shows you some things about the flywheel. The damn thing(clutch plate) did feel like it was coming apart around starting at around 3-4000rpms....and got worse from that point. A Valeo kit solved my problem(the OEM manufacturer of the clutches put in our cars from GM). The LT4 knock offs from anyone other than Valeo does not appear to be balanced correctly.