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Clutch problems

I love my Chevy Chevette!
Posts: 10
Joined: 04/13
Posted: 04/24/13 03:12 PM


Can you help me out.

I have a brand new Mcleod Street Twin clutch, 3 finger, ceramic disks. With this system, I also purchased the SFI bell housing and aluminum fly wheel.
The  engine is a professionally built 427 small block, dino'd at 710 HP.
The trans. is a Lenco, 4 speed ST 1200
The engine and trans. have solid mounts
All parts never on road

The problem I am having is when I release the clutch, the fork vibrates so violently that it broke the pivot ball and bent the rim of the throw out bearing.
I removed the trans, removed and reinstalled the clutch, but the fork rattle was the same when I engaged the clutch,
Any suggestions on what might I might be doing wrong?  

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I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 04/24/13 06:21 PM

Sounds like the clutch fingers are not level. Do they all touch the throwout bearing evenly? Is the input shaft straight? Does the input shaft fit in the pilot bearing correctly? There also has to be some clearance between the throwout bearing and the clutch fingers when released.
I am not familiar with that clutch, does it have individual adjustments for the clutch fingers?
A Lenco is a serious transmission! Are you running this in a drag car?
I had a friend with a Pro Mod who was running a Lenco in his car. He ran so much static pressure on his clutch it was burning out the thrust facing on the rear main bearing. He thought there was a problem with the engine which I then bought from him. I had no problems with that rear main. His next engine did the exact same thing. I repeatedly said to him what the trouble was and it took him a long time before he listened.
He works as the clutch setup man for a big dollar Pro Mod team believe it or not.
They fly him to different locations, pay his expenses and a fee for his services.  

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I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 04/24/13 10:49 PM

i wonder if the BRAND new components have worn thru their grinding marks yet...

perhaps the grinding marks are serious enough to cause HORRIBLE clutch chatter..  as the ceramic discs have no marcel as i recall..   they are engaged or not engaged..

what model dual disc set up.. part number..   i don't keep track of every model clutch  out there in my head...

does it have straps from the floater plate between the discs have  to the flywheel ?? to keep it from rattling around..

you might end up having to slip the clutch a few times to break in the wear and machined surfaces..

lastly...  can you recheck the crank shaft end play...

and did you indicate the location of the bell housing vs transmission alignment ring..

if you don't have a dial indicator...

figure out the correct size thread for ONE flywheel to crank shaft bolt...    weld another bolt to its head...   with a jam nut on the bolt going thru the flywheel ... so it does not go too deep...     on the bolt sticking up thru the alignment ring.. place a NUT... and several washers... usually some fender washers with a larger diameter washer between them and another nut...   so it nut.. fender washer.. big washer fender washer nut..

set the height so the big washer is right in the middle of the bell housing alignment ring...   place a feeler gauge between the washer and the inside of the alignment ring.. lock it the upper nut.. so the big washer is held tight..

you can now.. rotate the crank and check with a feeler gauge.. the distance /alignment..  and get it really close.. don't forget.. there is a tiny amount of clearance between the main journals and main bearing bores..  0.0015 or 0.002..   perhaps more..  you can still indicate it with feeler gauges to see if you are close for under 10 bucks in nuts bolts and washers if you don't have a dial indicator set and a magnetic base..    you have spent a LOT of money on engines and transmissions.. and i am giving you the LOW buck way to indicate a bell housing.. why.. i don't know..

so. i wonder to the race engine builders  how much does the crank sit below center depending on the main clearance..   does it matter if the crank indicated with the engine horizontal.. or does it come out better with the block sitting on the bench nose down..  up on bolts sticking out of the water pump and front engine mount holes so you don't have the snout needing a hole drilled in the work  bench..

lastly.. the bearing retainer on the front of the LENCO..  how is the fit of the throw out bearing on the bearing retainer sleeve..   i know that some bellhousings have the bearing retainer and sleeve the throw out bearing slide on bolted to the bell housing ???

and lastly.. how tight does the bell housing fit the lenco with the mounting bolts loose or trial fitting.. any slde to side clearance???  should not be..  but a slip fit..


then i spotted this...

Bruno Conversion Kit

hmm.. a torque converter for a lenco transmission..  hmm...  

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