I'm very tired right now, but after tearing down my block and taking it to a specialist here in the UK it looks as if my LT1 Intake Conversion has cost me the engine.

Gen1 Flat Tappet, 2pc Rear Seal...

To cut a long story short, it looks as if the distributor hole wasn't 100% perfect. Although there are no grinding marks on either Distributor Gear or the Cam gear something was making the Cam "walk" backwards/forwards.

The end result is I've got a snapped timing chain, every tooth broke off of the Crank sproket... and the casting behind the Cam sproket has been chewed away and groved. The sproket must have been grinding away at it.

I'm getting the casting re-leveled so I can use the block again, but I'm VERY concerned about using the LT1 Intake manifold again. I'm converting to a Roller Cam, retro fitted with Comp Cams Retro Roller Lifters but I don't think thats going to make any difference.

 

did you have a cam button or some other means of preventing the cam from moving? the distributor being slightly off shouldn't have caused that. they used to mount them straight up on the modded intakes till it was realized that it was creating an oil leak.

 

if the cam gear or dist. gear have unusual wear patterns on them or chunks taken off the gears i would not suspect the machining of the intake to be the cause. does the cam have unusual wear on the rear journals or are the rear cam bearings showing excessive wear on them compared to the middle and front? were your timing gears lined up properly? timing chains do fail!
i hope you do not have any other problems below,put her back together use a cam button and let her fly.....

 

I will check the cam when I get a chance. I couldn't see anything obvious though. I don't know anything about the timing gears as I'd never been into see. It seems strange that I've put probably 6,000 miles on this engine personally, and only 500 since the LT1 intake?

I'm converting to a Hyd. Roller cam with retro lifters, cam button and torring bearings. I hope this will stop any further problems.

 

i really think it was coinsidence,the parts you listed are good what about a new CLOYES double roller chain?

 

I've gone with a JEGS double roller and 9 keyway torrington bearing timing set. I've not heard anything bad about the JEGS stuff so I hope it will be OK

 

The block aligns the distributor. The intake adjusts the depth. If the distributor drops into place and the wear area on the distributor gear is centered (where the cam & distributor gear mesh), then it is OK.

A flat tappet cam has the lobes ground on a slope (front to back). This pulls the cam toward the rear of the engine and spins the lifter. The lifters are also crowned on the bottom.

RBob.

 

Was the thrust plate loose or even on there? I remember someone that rebuilt an engine without putting the plate on. Caused some severe damage.

 

Thrust plate not required for a flat tappet. Wouldn't fit the cam or block anyway.

RBob.