Cam Pitting
11-20-2001, 09:53 PM
#1
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Cam Pitting
I bought a low mileage '81 SC and noticed bad pitting on the #4 intake lobe. It almost
looks like non fill when it was cast. I can't believe Porsche would assemble the engine
with a bad cam, so I assume it's from lack of lubrication. I've noticed in other posts
regarding valve jobs that welding and regrinding cams is sometimes necessary. Is this a
common problem in the '81 SCs? Is welding and regrinding a common fix? I'm a
machinist and it seems to me that welding a cam would warp it. The car runs great, but
eventually the problem will have to be addressed. Thanks (in advance) for the help.
looks like non fill when it was cast. I can't believe Porsche would assemble the engine
with a bad cam, so I assume it's from lack of lubrication. I've noticed in other posts
regarding valve jobs that welding and regrinding cams is sometimes necessary. Is this a
common problem in the '81 SCs? Is welding and regrinding a common fix? I'm a
machinist and it seems to me that welding a cam would warp it. The car runs great, but
eventually the problem will have to be addressed. Thanks (in advance) for the help.
11-20-2001, 10:01 PM
#2
Instructor
I'd imagine the cams have a hard surfacing treatment at time of manufacture. This layer is probably not that deep. I'd suggest there may have been a lack of lubrication at some time in this motors life.
11-21-2001, 01:36 AM
#3
RL Technical Advisor
Originally posted by unirig:
<STRONG>I bought a low mileage '81 SC and noticed bad pitting on the #4 intake lobe. It almost
looks like non fill when it was cast. I can't believe Porsche would assemble the engine
with a bad cam, so I assume it's from lack of lubrication. I've noticed in other posts
regarding valve jobs that welding and regrinding cams is sometimes necessary. Is this a
common problem in the '81 SCs? Is welding and regrinding a common fix? I'm a
machinist and it seems to me that welding a cam would warp it. The car runs great, but
eventually the problem will have to be addressed. Thanks (in advance) for the help.</STRONG>
<STRONG>I bought a low mileage '81 SC and noticed bad pitting on the #4 intake lobe. It almost
looks like non fill when it was cast. I can't believe Porsche would assemble the engine
with a bad cam, so I assume it's from lack of lubrication. I've noticed in other posts
regarding valve jobs that welding and regrinding cams is sometimes necessary. Is this a
common problem in the '81 SCs? Is welding and regrinding a common fix? I'm a
machinist and it seems to me that welding a cam would warp it. The car runs great, but
eventually the problem will have to be addressed. Thanks (in advance) for the help.</STRONG>
This is not uncommon, I'm afraid.
Its usually caused by either a plugged up cam tower spray bar or camshaft surface hardening failure. The former is far more common than the latter.
The tiny openings in the cam tower spray bar that directs pressurized oil to lubricate the camshaft and rockers gets plugged up from infrequent oil changes and in some cases, poor quality oil.
The only fix is to remove the cam tower itself and pressure clean it followed by hand cleaning with special brushes. This clears the little tube of built up sludge and gak. The camshaft can usually be repaired by a competant cam grinder like Web-Cam or Elgin.
