63 340 2 head gaskets
02-02-2014, 09:36 AM
#1
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63 340 2 head gaskets
I know I read something about this years ago but can't find it. I just took my 340 engine apart yesterday, it was never apart- never and both heads had 2 steel head gaskets why did GM do that? car is late 63 over 20,000. Thanks
02-02-2014, 09:43 AM
#2
Race Director
lower the compression ratio...to do that they used two steel shim gaskets....I found this out with my FI 62 when I changed the heads with a new set of 64`s in 64.....One way to actually know that the engine was never apart
02-02-2014, 10:04 AM
#3
Burning Brakes
I'm confused. Are you saying that since there was two gaskets that it means it had been into???
Original compression ratio on 340 hp was supposed to be 11.25 to 1
For it to be a factory set up it should only have one gasket correct?
Just trying to learn all I can about the 63 340 engine
Thx
Original compression ratio on 340 hp was supposed to be 11.25 to 1
For it to be a factory set up it should only have one gasket correct?
Just trying to learn all I can about the 63 340 engine
Thx
02-02-2014, 10:55 AM
#4
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The two head gaskets were OEM on the '62-'63 327 SHP engines. I think this started shortly after '62 production started but not sure.
Early 409's used the same trick.
Supposedly, the reason was to lower compression to compensate for poor gasoline in some areas of the country. Must have been really bad as I built three of those engines in the early '60's from OTC parts and used one head gasket with normal premium fuel no problem. Even today, these engines run fine with one gasket on the gasoline many curse for being poor quality. 93 E 10.
Early 409's used the same trick.
Supposedly, the reason was to lower compression to compensate for poor gasoline in some areas of the country. Must have been really bad as I built three of those engines in the early '60's from OTC parts and used one head gasket with normal premium fuel no problem. Even today, these engines run fine with one gasket on the gasoline many curse for being poor quality. 93 E 10.
Last edited by MikeM; 02-02-2014 at 10:59 AM.
02-02-2014, 11:06 AM
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My former '63 327/340 had two head gaskets. 
Dennis
Dennis
02-02-2014, 12:59 PM
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02-02-2014, 01:18 PM
#11
Melting Slicks
Nothing like having it in print.
However.....todays driving conditions are quite a bit different from 1962. Cognizant builders will/should use a different approach to building this style engine taking into consideration many factors on how the car will be driven.
02-02-2014, 01:32 PM
#12
Burning Brakes
Care to elaborate on this???
02-02-2014, 02:40 PM
#13
Drifting
Thats why I laugh when guys with 340hp cars keep quoting 11.1 to 1 compression and what not. When I calculated my 340's actual compression it was 10.25. Runs great on pump gas.
02-02-2014, 05:37 PM
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Thanks. I have that piece of paper you posted but I'm far too lazy to dig it out!
Now, am I right about the 409's having the two head gaskets per side? Seems I remember an acquaintance that bought a new '64 409 and it had two head gaskets on it. "Nother guy bought a new '62 and it had two.
My memory dims with each passing year.
Now, am I right about the 409's having the two head gaskets per side? Seems I remember an acquaintance that bought a new '64 409 and it had two head gaskets on it. "Nother guy bought a new '62 and it had two.
My memory dims with each passing year.
02-02-2014, 10:18 PM
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The need to change the lash settings doesn't make any sense to me. Setting it to whatever was stock would just have you turning the nut a little further. If anything, it adds a little duration to the cam and makes it low speed power worse in addition to what it lost with the lessened compression.
Yes pushrods are now a little short..but that shouldn't affect cam settings.
JIM
Yes pushrods are now a little short..but that shouldn't affect cam settings.
JIM
02-02-2014, 10:20 PM
#18
Drifting
Thanks. I have that piece of paper you posted but I'm far too lazy to dig it out!
Now, am I right about the 409's having the two head gaskets per side? Seems I remember an acquaintance that bought a new '64 409 and it had two head gaskets on it. "Nother guy bought a new '62 and it had two.
My memory dims with each passing year.
Now, am I right about the 409's having the two head gaskets per side? Seems I remember an acquaintance that bought a new '64 409 and it had two head gaskets on it. "Nother guy bought a new '62 and it had two.
My memory dims with each passing year.
Verne
02-02-2014, 11:09 PM
#19
Safety Car
The need to change the lash settings doesn't make any sense to me. Setting it to whatever was stock would just have you turning the nut a little further. If anything, it adds a little duration to the cam and makes it low speed power worse in addition to what it lost with the lessened compression.
Yes pushrods are now a little short..but that shouldn't affect cam settings.
JIM
Yes pushrods are now a little short..but that shouldn't affect cam settings.
JIM
Fact is, the 097 cam is much too mild a cam to tolerate 11.25:1 SCR. It's much too mild a cam to tolerate 10.5:1 SCR, so the lash setting gives GM some extra leeway, or margin for detonation resistance taking into account the more sloppily built engines that were herded "out the door" back in the "good old days".
