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Cylinder gaskets to block 140 motor
Posted by: monzadon ()
Date: May 18, 2020 12:13PM

I am getting ready to put my 140 motor back together, i got my gasket set from Clark's, my question is originally there were 5 cylinder to block gaskets that measure about 30 thousands but the kit Clark's sent me has only one 10 thousands gasket, would it be a problem using the thinner gasket, i realized it will raise the compression

Re: Cylinder gaskets to block 140 motor
Posted by: jjohnsonjo ()
Date: May 18, 2020 12:25PM

The 10 is probably a cylinder base gasket. If that is the case, it won't work. Also, the crush to about 32 and should be thicker than that to start, unless they are the copper ones.

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


Re: Cylinder gaskets to block 140 motor
Posted by: cnicol ()
Date: May 18, 2020 12:33PM

.010" is correct for cylinder base gaskets except for a/c engines which had thicker base gasket to lower compression. Cylinder base gaskets have virtually zero crush.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

Re: Cylinder gaskets to block 140 motor
Posted by: jjohnsonjo ()
Date: May 18, 2020 01:22PM

jjohnsonjo Wrote:
-------------------------------------------------------
> The 10 is probably a cylinder base gasket. If that is the case, it won't work. Also, the crush to about 32 and should be thicker than that to start, unless they are the copper ones.


Reading my own post again, what I meant was stock head gaskets will be about 32 after they are crushed and more before, so I'm not understanding why your new un-used gaskets would be 30

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


Re: Cylinder gaskets to block 140 motor
Posted by: 66vairman ()
Date: May 18, 2020 01:26PM

cnicol Wrote:
-------------------------------------------------------
> .010" is correct for cylinder base gaskets except for a/c engines which had thicker base gasket to lower compression. Cylinder base gaskets have virtually zero crush.

I might be wrong, but didn't the late 65 and 66 A/C cars with 110HP engines and PG go back to standard cylinder base gaskets and instead came equipped lower compression 95HP heads?

Re: Cylinder gaskets to block 140 motor
Posted by: Phil Dally ()
Date: May 18, 2020 01:32PM

I learned something...thank you!!!

Re: Cylinder gaskets to block 140 motor
Posted by: Timothy Shortle ()
Date: May 18, 2020 01:43PM

I have read this topic 3 different times and am not understanding what is being asked or said. You should have 6 of the same cylinder base gaskets. Maybe Clarks made a mistake in their packaging?

Re: Cylinder gaskets to block 140 motor
Posted by: monzadon ()
Date: May 18, 2020 01:54PM

When i tore the motor down it had 6 gaskets under each cylinder that measured about 30 thousands and Clark's sent me 1 gasket per cylinder that measures about 10 thousands

Re: Cylinder gaskets to block 140 motor
Posted by: TerribleTed ()
Date: May 18, 2020 02:16PM

monzadon Wrote:
-------------------------------------------------------
> When i tore the motor down it had 6 gaskets under each cylinder that measured about 30 thousands and Clark's sent me 1 gasket per cylinder that measures about 10 thousands

Stock is one cylinder base gasket on each jug. The question becomes why did someone previously stack so many of them. Was the clearance needed? Did you have machining done that would make more clearance be needed like surfacing the head gasket seats? Precise measuring and calculation is you friend here.

---------------------------------------------------------------------------------------------------------

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I have personally performed ground up restoration on over 20 Corvairs.
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Re: Cylinder gaskets to block 140 motor
Posted by: corventure Dave ()
Date: May 18, 2020 03:02PM

Sounds like you have the thicker cyl base gaskets. If the engine was apart and worked on by someone before... it was not all that uncommon to put thicker cyl base gaskets in to lower compression. The old mickey mouse way was to stack head gaskets. But that lead to head gasket leaks. So thicker cyl base gaskets was an alternative.
Back in the gas line days, people ran regular cheap grade gas to save money. An easy way to try to reduce ping was stacking gaskets.

Corventure Dave

Re: Cylinder gaskets to block 140 motor
Posted by: vairmech ()
Date: May 18, 2020 05:27PM

monzadon Wrote:
-------------------------------------------------------
> When i tore the motor down it had 6 gaskets under each cylinder that measured about 30 thousands and Clark's sent me 1 gasket per cylinder that measures about 10 thousands
>>>>>>>>>>>>>>>>>>>>>

As has been said "stock" is 1 base gasket. If there were multiple gaskets under the cylinders someone has been into the engine.

The reason Clark's only sent one is because that is stock.

I think we need to know a little more about the engine parts you have specifically the heads. Post a picture of the combustion chamber.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

Re: Cylinder gaskets to block 140 motor
Posted by: larry202br ()
Date: May 20, 2020 11:43AM

Ken has a point. Stacking the base gaskets could be due to machining work performed on the heads.

1961 rampside with a 65 / 67 110 engine, car four speed.
1965 convertible
1966 Custom two door/four door 180 Turbo.

KC0SKX
Olathe, ks
HACOA

Re: Cylinder gaskets to block 140 motor
Posted by: JimBrandberg ()
Date: May 23, 2020 05:39AM

The correct way to do it is to CC the combustion chamber, measure the deck height of the piston below the top of the cylinder, choose a head gasket thickness and calculate the compression ratio. Online calculators have made it easy to adjust the variables.

You might want to approach it from the other direction, that is decide what compression ratio you want and then adjust the gasket variables to reach that goal.

Corvair head gasket surfaces often must be flycut due to the cylinder sinking up into the head. This changes the CC amount of the chamber. That's usually your place to begin.

There's piston top to squish chamber clearances that factor in sometimes too. Also valve to piston clearances but that's usually when changing to more of a camshaft.

Clarks lists stock steel cylinder base gaskets at .015 and copper at .020 and .032. The thicker gaskets give you more deck clearance.

The stock steel head gaskets are about .032. Copper are available in .032, .042 and .052. You can stack the copper ones if needed, not exactly ideal but sometimes you have to do something.

This is the short version. There's squish considerations as well.

You can hazard a guess that someone wanted to reduce the compression ratio so they stacked cylinder base gaskets. It's not a good way to do it, a single copper would have been better. Why they did that and if it was necessary is a mystery from here. You can either measure and figure it all out or take a guess and hope for the best.

I would first verify that the head gasket surfaces are good and then CC the combustion chambers on both heads.

Jim Brandberg
Isanti, MN
CorvairRepair.com



Attachments:
Re: Cylinder gaskets to block 140 motor
Posted by: jimc ()
Date: May 23, 2020 12:57PM

During my motor rebuild I was looking for .020 copper top cylinder head gaskets to raise the compression ratio, but none of our regular vendors had them. I found Gasket Works online at:

Headgasket.com

At that time they were same price as our vendors stock thickness copper gaskets. They were custom cut so I had to provide ID and OD and quality was great. The .020 was the thinnest copper they would cut.

Jimc
1965 Corsa

Jimc
1965 Corsa Coupe, two owner history


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