Hi all, new to the board but need some knowledge.
I installed a 94 LT1 out of a Z in a landcruiser. I probably lost most readers out there. However I am a loyal chevy guy with a 91 Z. Just experimenting with my off road side. Back to my question, Engine came with 6 speed, I couldnt use it due to the need of a transfercase etc, I used a 95 chevy truck flywheel and clutch topped it off with an NV4500 transmission used in one tons. All this equipment is new. The problem- has vibration just off idle. Took everything apart had flywheel balanced to original flywheel. Assembled, still has vibration. The engine ran flawless in the Z before removal. I have replaced every electronic component and had a dealer replace the opti distributor before swapping. Are the original clutches not neutral balanced? I am using solid mounts but have used the same on built 406's with nothing like this vibration. I have never heard of such vibrations occuring as I have read on this list. The problem exists sitting still. Havent tried putting on the original flywheel just for kicks yet. I know this is different than most posts but no one else has the knowledge of LT1's. Thanks for any info or suggestions.
thanks Andy

 

Could possibly be the pilot bearing. When my car had a bad vibration it was because of a damaged pilot bearing. After a couple hundred dollars in clutch and flywheel upgrades it ended up being a $15 part that was causing the problem. Good luck.

 

Good idea. I replaced with a new nonroller bronze bushing but took the parts departments word on the fit. I never actually measured the tolerance.
Thanks Andy

 

you may also consider the aligment between the crank and the trans i am a transplanter as well and have battled all the problems a time or two. Also when you got your flywheel balanced did you take the pressure plate and clutch disk with it?

just my 2 pennies

 

After talking w/ every machinist probably 60 or so I came to the conclusion that the clutch was neutral balanced in the LT1 as well as the GM clutch I installed. The shop that performed the flywheel balance told me not to bring the clutches that it was not necessary. I was also told that the flywheel balance on an LT1 was the same external balance as the new style crank(one piece seal) as the truck 350's and V-6's of the same year models. However the shop that balanced mine said it was different slightly with new drill marks to prove it. I wonder if they knew what they were doing? probably so.
I havent tried transmission alignment. The motor is mounted solid but the transmission can flex vertically slightly. What would you suggest I will try vertical and horizontal before I drop that thing on myself again, still hurts.
Thanks Andy

 

i have found with some conversion kits that the aligment of the bellhousing is not always real good so from time to time adjustable dowels are needed.
IF you have the engine out or trans for that matter her is what id do.

Get a dial indicator with a magnetic base and set it up so the base is on the flywheel and the dial is riding on the lip where the trans bolts up. That is with the bellhousing bolted to the engine. Then spin the motor by hand. You should get no more than about .002 runnout 0 is prefered, some people consider .007 acceptable. .002 seems the majic number for the lt1. if it is off more than about .005 buy a set of aligment dowels. Jegs and Summit both have them as will most speed shops.

just my 2 pennies.

BTW are you using any power or aftermarket pullies? If you are they may be suspect. Had a bad experience with them once and hear stories all the time. Just another thought.

 

The engine is stock except for the flywheel.
If this is not an alignment issue I can adjust with the crossmember It will definitly have to come out. Just cant stand the thought of going through the engine to replace the mains. Anyway your suggestion will rule out the bell housing not being true. Funny thing is its a factory chevy bellhousing with knew drilled holes to match the tranny, could have been a problem with his alignment of the holes. I'm getting that feeling your on to something.
thanks Andy