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Head gasket question...
Posted by: Grandpacorvair ()
Date: February 22, 2018 02:58PM

Rebuilt heads...new .020 pistons, cylinders bored out .020. Head rebuilder recommends using .052 gaskets because of today's crummy gas. That's .020 thicker than the original .032 gaskets.. I see Clark's also has .042 gaskets.

Opinions?

1964 Turbo engine....

Kerry Borgne
Birmingham, Michigan

1963 Spyder Convertible

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Re: Head gasket question...
Posted by: jjohnsonjo ()
Date: February 22, 2018 03:12PM

If it has factory turbo heads the CR is plenty low unless the machine shop really fly cut the registers. Go with stock and use steel not copper.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

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Re: Head gasket question...
Posted by: corventure Dave ()
Date: February 22, 2018 03:58PM

The other way to compensate is not to go with thicker head gaskets, but to go with thicker cylinder base gaskets.

Corventure Dave

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Re: Head gasket question...
Posted by: vairmech ()
Date: February 22, 2018 04:50PM

My question is, is the head builder a Corvair person that knows Corvairs?

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Head gasket question...
Posted by: 66vairman ()
Date: February 22, 2018 05:45PM

Kerry - I recommend you CC the heads and calculate the compression ratio (CR) BEFORE selecting head gaskets.

Bob Helt's book and other places tell how to calculate the CR based on cylinder bore and head chamber volume plus the head gasket size.

Feel free to ask more.

It's surprising how head chamber volume varies on rebuilds.

I bought a sand rail engine for little with some nice parts in it, BUT the heads CC'd to a 11.5 to 1 CR!!! A botched job.

Don't assume until you measure and good luck on the build.

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Re: Head gasket question...
Posted by: JimBrandberg ()
Date: February 23, 2018 04:13AM

I try to use the stock crushable steel head gaskets when possible rather than copper, although I don't think I've had trouble with copper even when stacked. I have provision for CCing combustion chambers and don't know how I'd ever just guess.

One of the main considerations is whether or not the head gasket surfaces have been flycut. One of the main concerns is whether or not they got all 3 even. I've had to use different thickness gaskets on the two sides to get the same volume.

I have a tall graduated cylinder for measuring, a plexiglass disc with a hole in the center that forms the top, a spark plug filled with epoxy and 4 1/4-20 bolts for leveling legs. Since I have all that stuff I don't wonder how else you would do it but there must be some other ways.

I don't know if I'd call small chambers a botched job, perhaps the gasket surfaces needed that much to true up or that was the goal. It can be difficult to mill that much out if you're trying for 11.5/1 in a race engine, they must be milled down almost to the spark plug holes which is to the deck and more.
As Dave already said, cylinder base gaskets are another way to add deck height for more volume if desired. I've got a straight edge with dial indicator tool for measuring that but I suppose feeler gauges would work. Stock seems to be around .010 a lot.

I learned how to do the math and used it as a reason for the children to pay attention in school but online C/R calculators have made me lazy.

With a turbo engine some folks might up the compression ratio a bit with some more sophisticated detonation control but that's a rabbit trail.

I'm sorry to be so complicated with what seems like an easy question.

I don't know why there isn't more discussion about head gasket surfaces, I hardly ever have them look good enough where they don't need to be addressed. Usually the cylinders have sunk up into the aluminum. Maybe I'm just too fussy but of course I don't think so.

After all that, jjohnsonjo may be correct to just use stock steel unless they look severely milled, maybe in conjunction with thicker cylinder base gaskets as suggested by corventure Dave.

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Head gasket question...
Posted by: Frank DuVal ()
Date: February 23, 2018 02:28PM

I've put many a head back on with the head gasket depression still on the head surface. With steel original type gaskets, they seal just fine for everyday driver use. Remember, that's what most of my customers did, drive their cars. This was before they were "collectible big buck trailer queens" that never leave the garage.

Frank DuVal

Fredericksburg, VA

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Re: Head gasket question...
Posted by: 66vairman ()
Date: February 23, 2018 04:34PM

Yes Jim the gasket surface was either milled into the spark plug holes or just nipping them. That's what I meant by "botched job". A shame as they were 140HP heads.

I suspect that, and other reasons, were why the owner never got the engine started. I ended up with some nice cylinders, rods, and brand new TRW forged pistons.

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Re: Head gasket question...
Posted by: joelsplace ()
Date: February 23, 2018 05:49PM

Those heads just need the proper combustion chamber milled into them after welding them up. If you don't want them I do!

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Re: Head gasket question...
Posted by: vairmech ()
Date: February 24, 2018 05:01AM

66vairman Wrote:
-------------------------------------------------------
> Yes Jim the gasket surface was either milled into
> the spark plug holes or just nipping them. That's
> what I meant by "botched job". A shame as they
> were 140HP heads.
>
> I suspect that, and other reasons, were why the
> owner never got the engine started. I ended up
> with some nice cylinders, rods, and brand new TRW
> forged pistons.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

What, like this????? I am still running these heads on my street car after running on the race track for 2 years. I don't think they were "botched".



Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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