1963 Corvair Head Compatibility

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'68_Corvair
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Joined: Wed Jul 29, 2020 8:37 pm

1963 Corvair Head Compatibility

Post by '68_Corvair »

Hi all,

A couple of weeks ago, my 1968 Corvair dropped both valve seats on the #5 cylinder. Luckily, the piston seems to be intact, but I may take it off to make sure the piston and rings are in good condition before attempting to run it again. The engine is kind of a frankenstein, but the "core" of the engine seems to be a 1963 84 hp engine. The driver side head (the intact one) is an 84 hp head. The passenger side head (the damaged one) is an 80 hp head, so I suspect that this engine had some problems in its previous life.

I managed to find a 1963 102 hp head locally. The head has sat in a shed for a long while, but it visually looks fine. Will I have any problems bolting a 102 hp head to an 84 hp engine? According to the CORSA Corvair tech guide, the 84 hp head and the 102 head seem to have the same compression. Will this mean that the head should be compatible, or are there other differences between the 84hp and 102 head that could cause issues? Surely it can't run worse than having two heads with different compressions on the same engine?

Head Info:

Damaged Head: #3813513
Compression: 8:1
HP: 80

Intact Head: #3813512
Compression: 9:1
HP: 84

"New" Head: #3813516
Compression: 9:1
HP: 102

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terribleted
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Location: Atlanta, GA
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Re: 1963 Corvair Head Compatibility

Post by terribleted »

Not a very good idea. The 102 head is not the same as the 84 head. Will it run sure it will, but, it may have some imbalance that will effect performance or durability. Heads should be in pairs not mixed. You can pair any 63 and before heads and mount them on your engine with the only issue possibly being cam difference as not all the different HP rated engines used the same cam. Even 64 110HP heads will fit and might even work ok but they are not ideal as the 64 engine has a longer stroke. Best way out cheap is to find a usable 84HP head or any usable pair 63 or earlier heads. If I was going to go farther (in to the cam for instance) I would find a late model 110 HP engine and rebuild it instead of doing major work or rebuilding the early short stroke engine.
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
Currently working full time repairing Corvairs and restoring old cars.
https://www.facebook.com/tedsautorestoration/

Located in Snellville, Georgia

'68_Corvair
Posts: 4
Joined: Wed Jul 29, 2020 8:37 pm

Re: 1963 Corvair Head Compatibility

Post by '68_Corvair »

Thanks for the info. I think I know where I can find another 102 hp head since mixing the two sounds like a bad idea.

I do actually plan to build up a 140 hp engine for the car and ditch the 84 hp engine, since that's what it came from the factory with, but I did not realize how unique the 140/auto engines are from 140/manual engines until I started gathering parts. Because of that, its taken longer than I expected for the engine to come into fruition. The 140 I'm building for it probably won't be ready for another 6 months, so I'm trying to make the current engine last until then.

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bbodie52
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Re: 1963 Corvair Head Compatibility

Post by bbodie52 »

When swapping cylinder heads remember that the outside cylinder barrel diameter changed in 1965. From 1961-1964 the cylinder bore (into the head) was 3-3/4". In 1964 the crankshaft stroke was increased to move the engine displacement from 145 CI to 164 CI, so the combustion chamber volume had to be adjusted to maintain the same compression ratio with the larger total volume displacement in each cylinder. The engine displacement remained at 164 Ci through the end of Corvair production in 1969. However, the cylinder bore into the head increased from 3-3/4" to 3-13/16" in 1965 to increase the head gasket contact surface area, so 1965-1969 cylinder barrels must match with the dimensions of 1965-1969 heads. 1961-1964 barrels fit properly into 1961-1964 heads and all years have the same piston diameter (bore) (except 1960 barrels, which were configured for only 140 Ci instead of 145 CI. The 1964 cylinder barrels were unique in the transition from 145 Ci to 164 CI, in that the outside diameter (into the 1964 head) was still 3-3/4", but the bottom of the cylinder barrel was notched to maintain proper clearance for the long-stroke crankshaft.

See page 6 of the attached CORSA Corvair Technical Guide 1+2 - Corvair Code Numbers for cylinder head details.

:chevy:
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CORSA Corvair Technical Guide 1+2 - Corvair Code Numbers.PDF
CORSA Corvair Technical Guide 1+2 - Corvair Code Numbers
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Brad Bodie
Lake Chatuge, North Carolina
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