I need some help here.
My freshly built 383 keeps wrecking Opti Bearings.
It has wrecked the bearing on the original Opti that had 260,000 miles on it (chalked this up to many hours); it also wrecked the bushing on a brand new Accel Opti (figured was a defect) and is in the process of ruining the bearing on a new GMPP opti all within 5,000 miles.
Naturally I'm getting an oil leak out of the front cover because of this.
WTF could cause this ?
My engine has the GMPP LT4 Hotcam kit and the drive pin is actually SHORTER (NOT long) than the spec of .405 to .450; it is .320 out of the cam face as measured by dial indicator according to my engine builder/mechanic.
My original 350 (which the block/heads are used in the 383) never had an opti problem

Here are my engine specs:
Original LT1 Block bored 030 over & honed w/deck plates, Align bored Mains.
Eagle Crank/Rods, Probe Forged dished pistons; 10.5/1 CR.
Stock LT1 heads that were ported, with bowls blended, guides teardropped, new bronze guides, 3 angle valve job, decked to true surface.
Stock intake/TB.
MAC headers
GMPP LT4 hotcam kit with 1.7RR
MadZ28 tune.
Denso O2 sensors
AC R44LTS plugs.
GMPP Extreme Duty LT1 Timing Chain/Gears
Comp Cams Roller Lifters

Any help would be greatly appreciated as a new $279.00+ labor opti every 2,000 miles is unacceptable.

 

I'm guessing you have a non-vented opti?

 

No, it is a vented Opti. that uses the cam pin to drive the opti.
My Car is a 1995 Z28.

 

Something doesn't sound right. This indicates the spec is 0.620". Would a 0.320" pin even engage the back of the Opti.

http://shbox.com/ci/cam_install.html

 

I may be off on my length dimensions; I will contact my mechanic to get the length again, but I do know for sure that he said the pin on my old stock cam is a fair amount LONGER than the pin in the GMPP LT4 hot cam. On one of the wrecked distributors you can see the wear mark where the pin fits into the drive slot and it is nowhere near bottomed out; the wear mark is barely past 1/2 deep into the slot.

 

Had a mistake on those dimensions; my pin is .580 in length, not the .320 I mistakenly listed.
Supposedly the length should be .620 to .685 according to Shoebox.
Can a too short pin have any implications as long as it spins the distributor ?

Any ideas why the opti bearings keep getting biffed ?

 

Is the timing cover messed up somehow to where the opti isn't centered on the cam?? Or maybe cocked? Are you "pulling" the new opti on with the bolts? Or sliding it into place and then putting the bolts in?

 

Not sure what you mean by pulling the opti into place with the bolts....my mechanic is doing the installs.

 

I have seen people do this, the opti won't slide in to place on its own so they put the bolts in and start tightening them up till the opti is in place. It usually wrecks the opti in the process.

 

I'm almost positive he is not installing it that way....it runs for a few hundred miles or so, then the front cover starts leaking again and you can feel the shaft vibrating when running by placing your hand on the front of the cap.
Could a worn front cover possibly be doing this ?
I have another much lower mile front cover that could be used.

 

Might be worth a try, something must not be straight. Maybe the opti hole is located properly or the cover is outta whack.

 

Something isn't right here. I wonder if the persistent oil leak and the early opti failures are related. I have heard of worn or improperly installed seals leaking, but not a worn out front cover. Does your engine builder have a lot of LT1 engine rebuilding experience? Just wondering.

Is your cam dowel perpendicular with the cam surface? It needs to be within the correct height, but also must be straightly installed. I've only done a few of them so I am not sure if it is possible to install then poorly, but something is really amiss that would kill bearings that quickly.

 

The cam pin is as installed by GM in the LT4 hotcam.
The engine builder has assembled several dozen late model LT1's but specializes in circle track racing engines.
My mechanic has installed several LT1's into F & Y bodies and has replaced several Optis.

 

maybe check the depth of the hole in the end of the cam where the shaft of the opti with the o-rings on it goes? and compare it to stock? something is putting a load on the bearings and wiping them out. no way do you get 3 of the same failure in such short mileage... either the problem is one of the parts involved or on the other side of the wrench, its time to break down and measure everything.