Keep wiping cam lobes *and not on a Buick*

[KevinB]

A buddy of mine has a '72 'Vette with a 350. We keep wiping cam lobes (Comp Cams kits, lifters, springs and cam). We do the proper break in @ 2000 rpms for about 20 minutes, use their assembly lube and even have added GM EOS. What gives?? The last one lasted for a week The heads were just off, looking for bent valves or any other defects. They were even rebuilt this time. Proper lash has been set each time also. This time the lash was even set a little loose (Zero, the a 1/4 turn). Anyone have any ideas? It does appear that the lifters are rotating as they should.

I think we will give it one more try, then go with a roller.

 

[suicide six]

What kinda spring pressures?Could also be comps cams.What are they saying about it?

 

[turboeric]

I've heard about certain year 454 big blocks, the lifter bores not being machined right. Never heard anything about small blocks. Maybe you have the same problem. Probably better off going with a roller set up.

 

[Sleeper1987]

I've heard about certain year 454 big blocks, the lifter bores not being machined right. Never heard anything about small blocks. Maybe you have the same problem. Probably better off going with a roller set up.

Bingo, have all the lifter bores checked. We just went through this with a 73 454 with a l88 solid cam 4 cams later and 2 trips to the machine shop no one could diagnose the problem or wanted to touch it. Even a minute misaligment will cause issues under pressure the 454 the lifters rotated fine untill they had the pressure on them. JMO but would be the first place i would look.


(Im sure they are a ton of spelling errors been a long day)

 

[gofstbuick]

Are you running stock cylinder heads? I know the valves are slightly canted on my AFR heads. If you use stock push rod guides on aftermarket cylinder heads with a slight canting, ths will cause a mis alignment problem. Maybe you have a core shift problem. Is there a torrington bearing behind the timing gear and a cam button? If so, is the block machined for the torrington bearing? How did you set the valve lash? to adjust intake: turn engine until exhaust valve just begins to open; to adjust exhaust: turn engine until intake closes 2/3s of the way. Add 1/4 turn at zero lash. Is the rear plug into deep? I'm just throwing ot some ideas.

 

[KevinB]

Are you running stock cylinder heads? I know the valves are slightly canted on my AFR heads. If you use stock push rod guides on aftermarket cylinder heads with a slight canting, ths will cause a mis alignment problem. Maybe you have a core shift problem. Is there a torrington bearing behind the timing gear and a cam button? If so, is the block machined for the torrington bearing? How did you set the valve lash? to adjust intake: turn engine until exhaust valve just begins to open; to adjust exhaust: turn engine until intake closes 2/3s of the way. Add 1/4 turn at zero lash. Is the rear plug into deep? I'm just throwing ot some ideas.

The heads are camel humps (462's) not stock but close.
We have not checked the lifter bores, but have honed them out. Thanks so far for the help

 

[quickt]

Would bet that you have coil bind of the spring or retainer to guide clearance issues.

 

[tommynos]

call steve at 941-921-race...he is here in sarasota,florida and is the "best" small block builder around and currently builds the motors for the 69 camaro baldwin motion cars,one was on the summit cover..he is a close friend of mine for many years,so just tell him i had you call(Tom Burnette) and he will help you...my small block in my jaguar did that twice and it was my lifter wasnt pumping up so i thought the rocker was loose and kept tighting it and it wiped out a lobe...good luck..

 

[1ARUNEM]

If you are running double or triple springs, use a set of weak springs (or take the center spring out) to break the motor in.

I would also have the lifter bores checked..

 

[chevyII]

are the connecting rod oilers facing the camshaft?