I have an 82-Z28 with the 305 (LG4-I Know, Whimpy).
I totally rebuilt the engine at 123,000 mi.
The problem was a worn down cam lobe on #8 exhaust. I put in all new GM valve train parts and a new GM High Performance 50 State legal cam.
After only 12,000mi. #8 Exhaust cam lobe is gone again.
Has anyone ever heard of this problem and do you have any ideas as to cause and or corrective action.

 

An unlikely suspect is the lifter bore, maybe something in there causing the lifter to hang up or something. More likely is a worn/damaged rocker arm ball/seat, or the rocker arm stud.

Might wanna make sure its getting oil too.

[This message has been edited by madmax (edited March 23, 2001).]

 

Skip,

Welcome aboard!

Max is there with good ideas (as usual). You might also want to see if the lifter bore angle is correct, in addition to the size and shape as Max advises. That is certainly not very good service from a cam lobe, and isn't normal.

The lifter body itself should be getting oil, since the galleries start at the rear end of the engine, but the cam lobe and face of the lifter may not be getting the shots from the con rod spurt holes on cylinders 7 and 8. Is it possible that the bearings, rod caps, or rods were installed with the oiling holes facing outward instead of inward?

Just a thought.

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

I've got this same prob. with my Trak Auto piece of rebuilt motor. Gone through a couple cams, same lifter too. The best suggestion i got was like above - a lifter bore issue, and perhaps honing it out would help. The only other thing i can think is that there's a prob with the oiling passage. It had a prob in stock trim and after changing heads, cam, etc. Had i known it was probably a block issue, i wouldn't have bothered to hop it up...

No worries though, a ZZ4 is in my near future!

-Rich

 

clogged oil passage feeding that lifter bore.

 

Madmax may be right. All through the 70s, one or more lifter bores in a block that weren't bored correctly was an extremely common situation. I had 2 3970010 350 blocks with this problem.

There are only 2 solutions I know of that are even remotely near practical. The obvious oneis to get a new block. The other is to have the lifter bores drilled out by a racing machine shop to use AMC lifters, which are a slightly larger diameter.

Also, it is possible that the first lifter, when it wiped out, damaged the bore.

There's no way it can be a clogged oil passage. There is one long passage that goes all the way from the bell housing flange to the timing cover, about 3/8" in diameter, that feeds all the lifters on the right bank, and a similar one on the left bank. The lifter bores intersect this passage. The ol is fed into it at the rear cam bearing and moves frontward through the block, passing around each lifter on its way forward. The entire right bank gets its oil fed to it around the narrow part of the #8 exhaust lifter.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Thanks for all the info guys. The possible causes are depressing though.
Max, I replaced all the rocker arms/ball seats and push rods with GM self aligning rockers and heavy duty push rods from the GM High Performance Catalog.
It has all new cam bearings and the block was boiled out so I don't believe the oil passages are blocked. The condition is limited to #8 exhaust. When I put it back together, I had marked all the caps and rods so I could reassemble them as they were originally. If the rods and caps are assembled wrong, they are as built from the factory.
I guess I should have gone for the ZZ4 retrofit kit as I originally planned. I thought I would save a few bucks by rebuilding and hopping up my old 305.
If the lifter bore in the block is the problem, I have wasted a lot of time and money.
If anyone has any possible fixes short of a new block, I would appreciate ideas!
Thanks Again,
-Skip