Comp Cam with all lobes measuring different???
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Teching In
Joined: Oct 2012
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Comp Cam with all lobes measuring different??? I am in the middle of rebuilding my engine, decided to mic all the lobes, and found significant variation in lobes; here is what I found from the front of the cam: .491 .497 .474 .466 .473 .471 .501 .502 .490 .492 .475 .471 .472 .473 .497 .497. The cam is a Comp Cams 08-503-8 XR276HR (SBC Cam not LS , but a lot of intelligent people on this forum) that has only about 2000-2500 miles and shows normal run in tracks that cannot be felt with your fingernail. This puts the exhaust lobe variation at .012” and .009” for the intake. I did measure the base circle of the .502 and .490 lobe and found .012” variation again which makes me think that the cam would not clean up so they ground more material off the cam. Does anyone have any explanation to why the lobes would vary so much?
I am in the current process of putting a lot of money in this engine and really hesitant to reuse it, even when it has almost no wear. The engine builder is talking with Comp, but would like to get some other opinions so I know if they are blowing smoke up my a$$. Thanks for help and input.
I am in the current process of putting a lot of money in this engine and really hesitant to reuse it, even when it has almost no wear. The engine builder is talking with Comp, but would like to get some other opinions so I know if they are blowing smoke up my a$$. Thanks for help and input.
Thread Starter
Teching In
Joined: Oct 2012
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Thanks for the link good info and a little scary, but sounds like user error too.
Endless amounts of info on here and done quite a bit of searching, but have not seen any posts about lobes differing in size.
Endless amounts of info on here and done quite a bit of searching, but have not seen any posts about lobes differing in size.
Thread Starter
Teching In
Joined: Oct 2012
Posts: 7
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After reading the other forum and after talking to couple cam grinders about the cam ramp causing the valve to possibly bounce on the seat. I decided to change cams to a different brand.
I did work with the machine shop to get the cam sent back to Comp Cams to have it CMMed and it came back out of Comp Cams tolerance. Comp Cams was willing to regrind the cam to make it right, but said I wouldn't notice the difference and that it normal for an catalog cam. I have deiced to not use any more Comp Cams products. I do give the props for admitting that the cam was out of spec though.
I did work with the machine shop to get the cam sent back to Comp Cams to have it CMMed and it came back out of Comp Cams tolerance. Comp Cams was willing to regrind the cam to make it right, but said I wouldn't notice the difference and that it normal for an catalog cam. I have deiced to not use any more Comp Cams products. I do give the props for admitting that the cam was out of spec though.
