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Cam much wear is too much?
Posted by: Grandpacorvair ()
Date: December 23, 2017 05:52AM

First let me say this picture is NOT of my current project! It's just a representation..

My questions is what amount of galling/roughness is allowed..if any? I'm trying to determine the health of my case and don't know what to look for re:cam journals.

Whats the best way to 'clean' the journals without removing too much metal?

Kerry Borgne
Birmingham, Michigan

1963 Spyder Convertible

Edited 2 time(s). Last edit at 12/23/2017 12:30PM by MattNall.

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Re: Cam is too much
Posted by: vairmech ()
Date: December 23, 2017 05:59AM

The visual tells me to much. That is something that you really need to see in person to make a positive assessment. Is the wear measurable?

Ken Hand
Handy Car Care
248 613 8586

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Re: Cam is too much
Posted by: 2ragtops ()
Date: December 23, 2017 08:49AM


A while back, I sold a case to a guy building an experimental aircraft.
He returned it saying the journals were too far out, I don't remember the values right now, but they were in excess in the fourth place of the decimal [ten thousandth's ???]

I gave him several more, and he returned them all saying they were not suitable for aircraft use, he was taking advice from Wm Winn in Florida.

Two of those cases have since been built into car engines and they are just perfect.

Take advice from Ken, follow his lead, you will be good to go.

Bob Bauer

Show-Me Corvairs

1966 Monza Convert 140 P/G with A/C, plastic wheel with tele-column am-fm posi-traction
1966 Corsa Convert 180 wood wheel tele-column am-fm sport steering posi-traction
1965 Corsa Coupe Crown V8 mounted mid-body temporarily red lined for repair
House Springs, Missouri

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Re: Cam is too much
Posted by: Nickshu ()
Date: December 23, 2017 08:54AM

When I did my engine I put the case halves together and measured the cam journals with a bore gauge to verify roundness, as well as measured at 4 different locations on each bore with four strips of plastigauge to look for differences. Mine did have some differences ranging from 0.0018" to 0.002". I think the acceptable max clearance is 0.002". Remember the cam is really riding on a film of oil, or at least it should be.

1964 Monza Spyder Convertible #435 - Rotisserie restored - Check out my restoration thread here: []
Recreational Mechanic/CORSA Member/COG Supporting Member/US Navy Veteran
Other fun car: Porsche 911 GT3
Boring daily drivers
Northern Colorado, USA

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Re: Cam is too much
Posted by: 66vairman ()
Date: December 23, 2017 10:46AM

Aluminum is a good bearing surface.

If you don't have a bore gauge to check for roundness - remember more pressure is exerted pushing the lifter so place the plastigauge on the same plane as the lifter bore.

Usually the the greatest wear will be at the cam gear end. Typically the journals are within spec. albeit sometimes at the max. The two gears are trying to push themselves apart - so measure on that plane.

BTW - ALWAYS check a cam (new or used) for out of round using "V" blocks. They can bend if handled roughly.

Just my 2 cents for what it's worth.

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Re: Cam much wear is too much?
Posted by: Brizo ()
Date: December 23, 2017 04:16PM

Grandpacorvair, I know that's not your crankcase and the pic isn't very sharp but the bearing surface looks very typical in my experience, with the shiny areas being where the cam and surface have touched at times, but only you can feel how rough it might be. As 66vairman said, the most thrust is on the front bearing but for the most part, the cam just floats in the center without much load on any of the bearings. Many years ago my crankcase had too much cam and main bearing clearance both, so I milled both crankcase surfaces to tighten them up.

Dan Brizendine,
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"

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Re: Cam much wear is too much?
Posted by: RexJohnson ()
Date: December 23, 2017 06:39PM

Years ago I rebuilt a '52 F Head Willy's Jeep 4 cyl and it had 1 cam bearing for the front next to the timing gears. The rest of the cam just road on the film of oil in the cast iron block.

RJ tools

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Re: Cam much wear is too much?
Posted by: viewmaster ()
Date: December 23, 2017 07:43PM

I have an RH block that looks like that, in the cam journals. Ended up mic'ing out tighter than 3 other blocks i tested. Bore gauge it, and then bore gauge it again, and see what the numbers say.


'65 '500' Sedan 110 PG
'65 Monza Sedan turbo'd 110 SU conversion
Fresno, CA

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Re: Cam much wear is too much?
Posted by: ken ()
Date: December 24, 2017 05:06AM

I have only taken apart 5 Corvair engines and they all looked like that . There is no quick fix . I put three of them together,good oil pressure, and they run just fine . It's not like a rod bearing banging on a crank. I doubt there has been an engine destroyed by a bad cam journal. The cam just goes round and round . None of the three will probably be driven over 10,000 miles in the rest of their time on Earth . Right or wrong, just my humble opinion .

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