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Old 09-04-2002, 05:43 AM
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Post Chevy Cam failures

I've recently had a couple of cam lobe failures with SBC circle track engines with flat tappet cams that I just can't figure out. I've heard the whole line about Comp Cams being soft(etc.) Well one was a Crane, the other a Reed cam. Two different engines. The break in's went normal, set the motor right at 2000-2500 for 20 minutes, plenty of lube on the lobes, (etc.) I have two thoughts/questions. Where should the lobe hit the lifter, toward the front of the block, on center, right of center? Also any thoughts on oil restrictors, my past experience's have been OK but now I'm beginning to wonder.

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Old 09-04-2002, 06:19 AM
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Was this only on one motor?
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Old 09-04-2002, 06:28 AM
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Two different motors
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Old 09-04-2002, 07:05 AM
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Engineczar,
Are the lifters turning in the bores, as they are supposed to? You can tell by looking at the wear pattern on the lifters. Also are you running very high valve spring pressures? For drag race engines I sometimes break in the cam with lighter springs, then change back to the stiff springs. Are your engines starting immediately as you first crank them, after installing cams? Cranking over excessively with the starter motor will begin the failure process. Engines primed well (including turning over by hand 2-3 revolutions, 90 degrees at a time, while priming)?
Other than that, it looks like you are breaking in the cams correctly. Hope this helps.
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Old 09-04-2002, 07:28 AM
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Due to track rules both engines required stock diameter springs. The seat pressures are in the 120-130# range for both. Tough to say on rotation at startup, the fit was good. If I take the bad lifter and turn it over and put it in the lifter bore the fit is ok and rotates easily. The worn out pattern is circular so I believe it was rotating as it wore. There's plenty of clearance between the retainer and guide also no coil bind. Both motors did have pretty aggressive profiles. Both had lift rules to follow, even though they were circle track motors the profiles were basically NHRA stocker profiles ground on tight lobe centers. This is why I'm questioning the oil resrictors.
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Old 09-04-2002, 07:55 AM
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You are right, the circular pattern on the bottom of the lifter indicates that it was turning. And your spring pressures are not excessive, soooo I don't know the answer. I have used restrictors for flat tappet and roller applications and have not experienced any problems. Good luck.

P.S. What are you using for assembly lube on the lobes and lifters? Good moly lube is the ONLY way to go here and coat BOTH the lobe and the lifter. Cam break-in needs moly lube, I still see some guys using engine assembly lube and even the white stuff (uuuugh).
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Old 09-04-2002, 09:44 AM
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Thanks, you can understand my problem. I generally use the breakin grease that Isky supplies. It's similar to Edelbrocks, Crane, and Reeds product. I didn't care for Comp Cams "Pro Lube" I found it to be too thin and dripped off the cam if the engine had to sit for any time prior to startup.
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Old 09-04-2002, 09:45 AM
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Thanks, you can understand my problem. I generally use the breakin grease that Isky supplies. It's similar to Edelbrocks, Crane, and Reeds product. I didn't care for Comp Cams "Pro Lube" I found it to be too thin and dripped off the cam if the engine had to sit for any time prior to startup.
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Old 09-04-2002, 10:14 AM
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ARE YOU PUTTING SOME ON YOUR FINGER AND COATING THE LIFTER BORE TOO? I GOT NO OTHER SUGGESTIONS.
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Old 09-04-2002, 11:28 AM
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Just on the face of the lifter. I put oil in the lifter bore and oil the OD of the lifter. My experience has been that moly on the OD of the lifter makes the lifter drag too much.
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Old 09-04-2002, 12:07 PM
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I agree, moly lube should be on the cam lobes and lifter faces. It is too heavy for the lifter bores, but Bull is right, the lifters and the lifter bores should be lubricated - I use motor oil, then pour some over the lifters after they are installed.
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Old 09-04-2002, 05:10 PM
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What kind of oiling mods have you performed on the engine? If you have a windage tray, blocked off drainage in the center of the lifter valley, or enlarged the end drain holes this can starve the cam of oil coming from the top end. You might try blocking off the end drains and force the oil to return onto the cam even though it uses some power. If your side clearance is very tight on the rods not enough oil might find it's way onto the cam, for racing you should use a heavy straight weight oil like 50Wt synthetic. Multigrades degrade under race heat and loads and won't stand up to high rpm abuse. Make sure the lifter edges are deburred well and the cam circle edges too, usually they are sharp from the factory. A few minutes with a fine grit sanding drum or honing stone helps a lot.

There are a million things that contribute to cam death but since you are seeing a complete degradation it suggests film failure. With cheater cams the lifter diameter becomes a major consideration and this is why special lifters with enlarged bases are made, they have to be installed from the bottom but solve many ramp acceleration related problems. Also if you run the engine into valve float it will destroy the cam quickly, this type of failure can be identified by spalling on the lifter face or cracking. If possible post a picture of a lifter and a cam lobe so we can see what type of metal failure you are experiencing.
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Old 09-04-2002, 06:20 PM
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[ September 04, 2002: Message edited by: hcheetwood ]</p>
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Old 09-04-2002, 06:21 PM
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This is probably a real dumb question. Are you installing new lifters with the new cam?
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Old 09-04-2002, 07:10 PM
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You're not using the oil restricters with hydraulic lifters are you? If you do they will starve the lifters.
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