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We have had a 454 engine rebuilt 4 times and each time after approximately 1000 miles, the cam fails. We have made sure to break the engine in properly, not to overrev, etc. etc. and each time the cam fails. This time after about 1200 miles, went to start and getting a popping sound. In times before, it would be under load before it started this, now it was just warming up. Anyone experience anything like this?
i had a problem with lifter bores to tight lifters would not rotate so cam failed I took small wheel cylinder brake hone went through all lifter bores and problem solved hope this helps........
I would check the cam bearings for alignment to oil supply ports and also look for obstructions (dirt etc.)in the oil supply galley to the cam. good luck.
I assume you're having lobe failures, is it always the same location(s) that fail(s)? If so, what location?
Regards, Mark
Is it bearings or lobes failing?
Thank you for the replies. They are lobe failures and different locations each time. We had a reputable guy to rebuild the engine and have been told the block is in excellent condition. Have replaced the distributor and untold other parts. Each time the cam would fail, we would go through the process of replacing spark plugs, wires, etc. first just to make sure. We are going to check it out this weekend and verify if it is in fact another cam failure. I'm sure we will once again be replacing plugs, etc. I appreciate you all taking the time to respond. If you think of any tips, let me know.
Well Mary, let's start with some basics. Is the cam coated with an appropriate break in lube when installed? What oil are you using during the break in period, initial fill, first change? Does the car have an oversize oil pan? How many quarts of oil are you putting in at each fill/change?
Random questions. . .
Have you checked for spring pressure, spring binding, rocker arm adjustment?
Are you using new lifters with the new cam?
Is the cam walking?
Are you breaking in the cam according to the manufacturer's instructions?
What kind of oil pressure do you get?
is your rocker geometry right should be in center of valve stem
do u have dual springs. comp tells me after i wiped a cam out
that break in should be done with the inner spring removed
It sound's to me either the valve spring's are way to strong for the cam or the cam isn't getting any oil . Make sure the oil feed cam holes aren't plugged with moly lube . Also make sure your oil pump is functioning properly and the screen isn't plugged with moly lube.:3dSMILE:
Is it the same rebuilder that has done each of these?? Big block chevy's are known for cam problems, but four in a row is a red flag for sure. If you're told the block is in excellent shape, what is he basing this observation on?? Something is wrong for sure, and it sounds like the lifters aren't turning, or not spinning enough, and the cam is going. There should be enough spash to lubricate the cam during normal driving, so the oil passages are not an issue with this problem. Sometimes a soft cam lobe or lifter is a problem, but not this many times in a row, and it's different lobes/lifters each time. If it were spring pressure, it probably wouldnt take 1000 miles for it to happen...I have wiped out cam lobes with heavy spring pressures within 15 or 20 minutes. Everyone here has brought up good questions to ask, but all of them should be a no brainer for an engine rebuilder. I hope he is doing something for you money wise???? I think it's time to look for another mechanic.
I agree if it is not oil or spring pressure, then I would definitely have the block checked by another machinist. Could it even be the line bore for the cam?