Cam Button Noise
Thread Starter
Cruising
Joined: Dec 2011
Posts: 14
Likes: 0
Cam Button Noise
Just wondering about this one. I just started up my Big Block after a rebuild and kept hearing this scrubbbing sound near the front of the engine. Got the stethoscope out and it is coming from the front of the timing cover. The engine has a 612/612 full roller valve train. I used a cam button with the bearing. While it was adjustable it was too much of a gap with all the shims in it. So I ended up very carefully hammering in the timing cover area where the cam button rides in order to get the clearance down to .004. Its a pretty thick stock cover which took some effort to alter so I am assuming it is a pretty solid solution. But now I have this scrubbing noise at idle. I read on line to adjust cam end play to .005 - .010. I figured .004 would be Ok. Any insiught on this? Thank you.
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
0.004 should be perfect, but are you sure it had that. If your lifter bores are not drilled correctly, the cam could be walking forward under a side thrust from the cam/lifter interface. "Cam Walk" as it is known is checked during assembly process. I always TIG weld a little button pad into stock timing covers when I run a thrust button.
Are you sure your water pump isn't loading the timing cover into the cam button, if it is, you need to space it out.
Are you sure your water pump isn't loading the timing cover into the cam button, if it is, you need to space it out.
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Did you use a timing gear with a torrington bearing on the engine side. BBC tries to pull the cam through the block for some reason. In the old days we used to have to mill a recess for the bearing, now you can buy the gear with it. You can drill an oiling hole to lube it. With a cam button you may be getting some noise from there. I'd address it before you get shavings wandering around.
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
I wouldn't think you could get any noise from that button. But I would be concerned that in the process of "dimpling the cover that you distorted the cover and maybe have the chain touching the cover.
Thread Starter
Cruising
Joined: Dec 2011
Posts: 14
Likes: 0
Well I got the cover off and found the problem. The darn chain was actually lightly scrubbing the cover on three of the stamped in spots. Fortunately it was only scrubbing lightly and very little metal actually flaked off...mostly just gauled up a little. The engine only had about ten minutes on it most at idle with a few revs up to about 2500. I think when I hammered in the center with a dead blow to adjust the cam end play it must have bent the whole face of the cover in just enough to make contact. I'm going to get a new cover now but thinking of getting one that I can adjust cam end play with. Any thoughts? It might sound dumb but I really don't want to tear off the intake to take measurments and would like to get a good cover to go with this roller system anyway.
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