cam journal scoring

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3gress
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cam journal scoring

Postby 3gress » Tue Jul 26, 2016 7:53 pm

I have this head sitting about and hope to give it a work over for a forced induction build. Ive used acl flexigauge to check the journals and they are in tolerance, lifter bores as well etc. The head came off a known healthy low k engine.
What concerns me is the scoring on the exhaust cam journals. The picture below shows the worst of the scoring, what do you guys think on it's worthiness?

Image

StillIC
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Re: cam journal scoring

Postby StillIC » Tue Jul 26, 2016 9:56 pm

IMHO:

Is there any metal proud of the surrounding surface? If so it needs to be smoothed off. If not don't worry about it. Get some 2000 wet and dry abrasive paper and give it a quick rub. That should tell you if there is any proud material, and will perhaps rub any marks out.

Some bearing faces have grooves machined in them for oil flow, so a little accidental groove won't hurt, especially on a camshaft journal.
WP:1.12.492 SMPN:1.16.403 SMPS:1.05.473 SMPGP:1.53.256 SMPB:2.22.181

manga_blue
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Re: cam journal scoring

Postby manga_blue » Tue Jul 26, 2016 10:51 pm

Mazda's spec for camshaft bearing oil clearance is 0.035 - 0.081 mm or 0.0014 - 0.0031". Ever heard of ACL Flexigauge?
’95 NA8

3gress
Racing Driver
Posts: 512
Joined: Tue Apr 14, 2015 6:49 pm
Vehicle: NA6
Location: northern rivers n.s.w.

Re: cam journal scoring

Postby 3gress » Wed Jul 27, 2016 12:30 am

I mentioned above using the acl flexigauge to check journal tolerance. It is similar to plastigauge. You lay a piece on the journal, install and torque cams to spec and then read the amount of crush by measuring the width against a graph on the flexigauge packet. A simple technique to determine wear in the journals. Micrometers were used to check lifter bores at several points. The cam bearing surfaces were checked, end lash also.
The scoring is due to the channels in the exhaust cam bearings. Since everything is nice and tight i could get away with a light pass over with emery paper to clean them up. Cheers fellas.

manga_blue
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Re: cam journal scoring

Postby manga_blue » Wed Jul 27, 2016 10:35 am

Sorry, obviously I didn't read your first post properly. If they're in spec then I'd use it. The scoring may mean there was some oil contamination. I would take out all the gallery plugs and give all the oil ways a serious clean out first.
’95 NA8


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