Two head gaskets real or myth?

oldskydog

Well Known Member
Supporting Member 9
#21
Pat,
A little research in the Feb, 61 P&A catalog (strangely revised Nov 62) shows head gaskets for early 61 409 qty 2 where the late 61 head gaskets qty 4. I'm sure the early engine had the 586 heads and the late version had 690 heads so it seems logical to say single gasket for 360 hp version and double gaskets for 380 hp and up (or anything with 690 heads). Also strange that there is no reference at all to early version 409 586 heads and I know they were still being cast as late as Dec 61 for service. Only 690 heads are listed for 61 409 engines but a note warns not to use 690 heads on early 409 engine.

http://www.gmpartswiki.com/getbigpage?pageid=65919
 

409gang

Well Known Member
#23
So guys I've always heard HP 409s had two shim head gaskets from the factory to drop CR. My first 64 was a 340 HP and only one.

Real or myth?
That article dated October 61 indicates all 409's in 62 (no 340hp in 62) which all were high compression engines 380hp and 409hp.
 
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427John

Well Known Member
#25
Pat,
A little research in the Feb, 61 P&A catalog (strangely revised Nov 62) shows head gaskets for early 61 409 qty 2 where the late 61 head gaskets qty 4. I'm sure the early engine had the 586 heads and the late version had 690 heads so it seems logical to say single gasket for 360 hp version and double gaskets for 380 hp and up (or anything with 690 heads). Also strange that there is no reference at all to early version 409 586 heads and I know they were still being cast as late as Dec 61 for service. Only 690 heads are listed for 61 409 engines but a note warns not to use 690 heads on early 409 engine.

http://www.gmpartswiki.com/getbigpage?pageid=65919
Valve pocket on the early pistons too small for the larger intake valves?
 

David Soper

Member
Supporting Member 1
#26
I took delivery of my 1962 ss 409/380 i on March 20,1962.The car felt slow.I called Bill Jenkins shop in PA and he laughed. He said the car motor had two head gaskets.He told to remove the head and gave me the part numbers for the proper gaskets. He also said to match port the intake manifold to the heads and replace the factory intake and exhaust springs. ALso the intake was a dual plenum he said to grind out the center section to make open plenum intake and change metering rods and adjust floats. The car felt fast and at Capitol drag strip it went 13.9 at 107 on stock tires
 

skipxt4

Well Seasoned Member
Supporting Member 14
#31
My 64 had 2 Head Gasket's, on each head. I should have left it, the way GM made it. :doh Ran much better, and fouled the plugs, less. Had better traffic manners.:appl But, I was a kid, and wanted the extra H.P.:rolleyes
 
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