62 cam lobe wipe out

[Duke W.]

Re: 62 cam lobe wipe out

Dan,

One other thing to think about is the high oil pressure could be caused by some restriction in the oil galleries that provide oil to the lifters and pushrods for up top valve guide/spring oiling.

Oil pressure is controlled by the relief spring in the oil pump housing. A restriction somewhere in the engine will not cause high oil pressure. It will just result in reduced oil flow, and if it's in the main gallery it would likely result in bearing problems.

In any failure analysis the first thing to look at is is the installed parts, Then you determine if the parts were built to spec. In the case of cam lobe failures, the first thing to do is determine the manufacturer and part number of all installed valve train parts, and it usually turns out to be an aftermarket cam with aggressive dynamics and gorilla valve springs, but guys want to believe that they used "good" parts and their "engine builder" is a guru, so they blame it on the oil, some exotic internal engine problem, Reaganomics,...whatever.

It's called DENIAL!

Duke

[Timothy B.]

Re: 62 cam lobe wipe out

Duke,

I agree that maximum oil pressure is controlled by the relief spring in the pump but high oil pressure is controlled by a restriction to flow like the bearing clearance so if there was a restriction in the tappet galleries or the drilling to the galleries from the rear of the cam bearing why would this not raise the oil pressure?

In the how to hot rod book it's recommended by one racing builder to plug and re-drill the holes going to the tappet galleries to something like .060 to reduce the flow of oil up to the heads for high rpm use. I think (not sure) there is a comment about higher than normal oil pressure.

[Duke W.]

Re: 62 cam lobe wipe out

Basic hydraulics. The gear type oil pump is what's called a "constant volume pump" If you give it a supply and just dump the output into a bucket, the delivery volume will be approximately proportional to pump speed until you get up the the point where it cavitates and output pressure will be very low because there is no restriction at the output.

Now if you place a restriction at the output - equivalent to the internal restriction in the engine, which is primarily a function of bearing clearance, rod end play, and lifter bore clearance, the pump will begin to develop pressure at the output at relatively low speed, and when the relief spring opens, excess output will be shorted back to the pump inlet.

In a properly designed engine oiling system, the internal galleries that feed oil to the cranktrain are NOT a major restriction to flow, but some designs may use internal restrictors to limit overhead oiling. Such is the case with my Cosworth Vega. Oil flow to the ten cam bearings is restricted by a .090" orifice, so not much oil is getting up there, but the cam bearings have relatively low loading and tight clearance, so they don't need much oil, and the direct acting valve train doesn't need much splash off the cam bearings.

The SB oiling system from about '57-on has proved to be very trouble free in normal road use. It was okay for early road racing too, but as tire adhesion went up, oil starvation became a problem because high dynamic forces pushed the oil away from the pickup. Racers resorted to all kinds of baffling and trick pickups, but it was finally dry sump systems that solved the problem for good.

Relatively high overhead oiling volume is necessary with the OE rocker system at sustained high RPM -as much for cooling as for lubrication. Everything I have read about restricting overhead oiling supply applies to the use of roller trunnion rocker arms on racing engines where the rules allow them. The needle bearings don't need much oil and don't generate as much friction and heat as the OE rockers at high sustained revs.

Duke

[Joe C.]

Re: 62 cam lobe wipe out

Since the guy installed what appears to be a high volume, high pressure oil pump, I'll bet he installed some aftermarket cam with aggressive dynamics and gorilla valve springs. Did he lower the compression ratio, too?

What is the cam model and cam manufacturer?

What are the valve spring force specifications?

These kind of stories about OE engines rebuilt with a bunch of aftermarket hot rods parts happen nearly every day, but guys keep handing their engine over to some "engine builder" and let him screw it up rather than managing the process and specifying OE equivalent parts from OE quality suppliers.

When new, these engines did not get any kind of "cam break-in". In fact, they got the absolutely worst treatment you can give to a new engine - many starts with short operating time, mostly idling, but lobe failures were extremely rare - almost unheard of with small blocks.

Duke

How do you know that it's a high volume pump? Evidently, it's a high pressure-standard volume pump by virtue of his oil pressure readings. Is certainly possible that it's a high pressure-high volume pump. But how do you know, for sure, that it is? Please enlighten us, as I certainly am now very curious.

It's not necessarily a "hot rod" cam, since I know of plenty of cases where vintage replica/reproduction cams have been wiped out numerous times during run-in. It is very possible that the OP didn't fortify his ordinary motor oil with EOS, or ZDDP additive for its break in cycle, or, didn't use dedicated ZDDP fortified break in oil.

[Joe L.]

Re: 62 cam lobe wipe out

I have a 62 with a 327 300 hp that was rebuit a couple of years ago and right out of the gate (less than 20 miles on it) it wiped out the exhaust valve lobe on the rear most passsenger side cylinder. The rebuilder came out and replaced the cam and lifters. I drove the car another 20 miles and then let it sit over the winter. When I started it up this spring, the lifters were knocking and again I found a lifter wiped out this time the exhaust valve lobe on the driver side rear most cylinder and the front most cylinder on the passenger side. Unfortunately, the machine shop went out of business and before I put another cam in this engine, I wanted to find out the real cause of these failures. I am aware of bad quality lifters and cams in the industry but I find it hard to believe that two in a row can happen. One of the other concerns I have is that fact that ever since they did rebuild this engine, the engine oil pressure is very high (50 psi at idle and up to 75 as the engine is rev.'d). Can anyone out there shed light on this subject?
Thanks in advance.

Dan------

First, I would check to be sure that the valve springs are the correct rating. If you know that the original valve springs were re-used, this will not be necessary. However, if they were replaced, you want to make sure they're the correct ones for the engine. All you need to do is to check one for correct open and closed pressure. I would also check to be sure that you have a standard pressure oil pump. If it's high pressure, all you need to do is to change the relief spring. If it happens to be a high volume pump (i.e. gears 1.5" long versus 1.3" for standard volume) change the whole pump to standard volume.

I would use the following for camshaft and lifter replacement:

camshaft: GM #14060651

lifters: GM #5232720

The above are the direct GM replacements for your 300 HP application and they are very high quality OEM parts.

I do agree with the others that you may need to insure that no metal particles are in the engine.

[John D.]

Re: 62 cam lobe wipe out

Melling oil pump: Stock # is M55. The key to an oil pump from other suppliers is not to have a suffix after the part number.
For example: NO M44HV and No M55S. Those are high flow and high pressure.
Want to mess up your FI car use one of those last two part numbers. Causes distributor leaks and other engine leaks.

[Joe R.]

Re: 62 cam lobe wipe out

Dan,

Maybe I'm wrong, but I would think you would need to tear down the engine completely and take it to a machine shop to get rid of as much loose metal as possible after flattening the cam. Did you do a post-mortem inspection on the oil pump and filter? In addition to the CJ-4 rec you already received, I would add a quart of GM Engine Oil Supplement (EOS) for break in.

Joe

Dan,

I said quart of EOS, but I really should have said can. I don't think the can is a quart. It's probably a pint.

Joe

[Joe R.]

Re: 62 cam lobe wipe out

Any cam manufacturer will tell you to use their lube and replace the springs and lifters when you replace the camshaft. Springs do NOT keep their original specs after +40 years. They have to be replaced when installing a new camshaft just to make sure the camshaft manufacturers specs are kept within limits. This does not mean to go out and use a Gorilla spring on a stock 300HP camshaft. Won't work ever!!!!!

JR

[Clem Z.]

Re: 62 cam lobe wipe out

any time you have engine work done demand a itemized listing with part numbers of the parts put into the engine so if there is a problem you have a idea where to start looking.

[Dan S.]

Re: 62 cam lobe wipe out

Thanks for the info Joe. Greatly appreciated..
Dan

[Philip C.]

Re: 62 cam lobe wipe out

Sorry Dan, a cam is the worst thing that can happen to a motor. I agree with Joe R above in #14 post he's right you have to clean that motor, that cam material is in everything and a BITCH to clean out of a motor. I would use a roller cam and nothing else. Good luck Phil 8063

[Dan S.]

Re: 62 cam lobe wipe out

Thanks Phil for your info and time..Dan

[Joe L.]

Re: 62 cam lobe wipe out

Sorry Dan, a cam is the worst thing that can happen to a motor. I agree with Joe R above in #14 post he's right you have to clean that motor, that cam material is in everything and a BITCH to clean out of a motor. I would use a roller cam and nothing else. Good luck Phil 8063

Phil and Dan-----


I like roller cams, too. In fact, I greatly prefer them to any flat tappet and, personally, I don't think I'll ever install a flat tappet again. There are some retrofit roller cams that will produce performance approximately equivalent to the 300 HP cam and some that will improve performance.

Retrofit roller cam set-ups are somewhat expensive but, for me, they are well worth it.

[Clem Z.]

Re: 62 cam lobe wipe out

if you use a solid lifter roller cam make sure that the rollers are full pressure oil fed as regular roller lifter needles are just splash lubed and they do not like low RPMs. also use a rev kit to keep the rollers in place in the lifter bores if you happened to loose a pushrod,rocker arm or rocker stud.

[Joe C.]

Re: 62 cam lobe wipe out

if you use a solid lifter roller cam make sure that the rollers are full pressure oil fed as regular roller lifter needles are just splash lubed and they do not like low RPMs. also use a rev kit to keep the rollers in place in the lifter bores if you happened to loose a pushrod,rocker arm or rocker stud.

Great advice, but I doubt if the OP would go with a solid roller since they generally have faster ramps and higher lift than hydraulic rollers. Even the mildest hydraulic roller would still be somewhat more aggressive than the 929 cam, while at the same time providing more durability than even the mildest flat tappet cam. Rev kits are not necessary with hydraulic rollers since engine speeds will generally prevent the lifter from losing contact with the lobe at POML, and the resultant catastrophic lifter shattering when it lands back on the lobe. I've used Comps Endure X solid roller lifters which are all pressure fed through a very small EDM hole injecting oil directly at the rollers and needle bearings. Another great thing about roller tappets is that there is no danger in installing standpipes in the lifter gallery oil return holes, which saves windage due to much reduced oil splash onto the crankshaft from above.

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