Thread: Cam Thrust Button

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Last time I put my big block together I used a Comp cam nylon thrust button. It was about .030 to long so I removed .030 from the cam side. The button fit tight in the gear when installed. I was going to reuse the button when I put it together this time but it doesn't fit tight in the gear. The button is about .004 smaller in diameter then it was originally. It looks like instead of turning with the gear, it turned in the gear. It's button is still exactly the same length as it was when I put it together last time. There is only a small contact point on the front cover. The front cover is an Edelbrock aluminum. Solid roller cam. The engine only had about 500 miles on it. What should I do this time?

you want the button end play to be less then 010 to all most 0 .i like the button to fit in the gear tigth .but if your running a lock plate it would be ok long as its not realy bad .i just use one of the BBC Edeldrock /china die cast covers .to say that it could be better is a under statement. i used a roller type button and set it at .005 i like to keep the end play under .010 on the roller buttons to get that cover to fit and machine the right end play i had over 3 hours in to a job that only takes one hour most of the time

Thanks Pat, I had the end play at about .008 last time. I thought maybe I didn't get the button straight when I filed the extra off. However, Comp cams nylon buttons have a flange that I measured and its within .001 so I must have got it fairly straight. Have you ever had a roller type button go bad? I'm thinking about using one when I put it back together. This time I'll take the extra length off in a lathe. I work in a machine shop but they seriously frown on home projects. I'll probably have take it somewhere else.

no. i never had one i put in go bad but like any thing they could .where you would see one fail is to much end play were the bearing do not like getting hit .i use solid buttons as well. i make them out of alum or plasic cut them out on the lathe with a alum cast cover i would use a nylon button or roller .with that cover a sbc botton may work better less to cut down . rollers i take them part and face the button .then make shims if needed to fine tune the end play in .i like to drill out the 1/4 npt lifter gallery plugs to 030 the this helps with air lock .but i use it more to help throw more oil on the chain and front button and cam thrust helps keep things happy