327/340 HP head number(s) clarification please

[Bruce D.]

Please help me with some head numbers for a 1963 327/340.
Casting number on both heads are 3782461 as I think they should be.
Both casting numbers have an additional 2 digit number sideways right next to them; one looks like a B7 and the other a B8 (or3).
The GM logo in the center of the head has numbers next to it; the driver's has a 3 and the other has a 4.
Where I would expect the casting numbers there seem to be 2 sets of numbers.
The GM 3 head has what looks like 13 or I3 and E28
The GM 4 head has what looks like 13 or I3 and E33 (this obviously can't be May 33).
Could they both be Jan 3rd? What is the E number?

Any detail explainations for the various numbers that appear in addition to the correct casting numbers would be appreciated.

thanks

[Joe L.]

Re: 327/340 HP head number(s) clarification please

Please help me with some head numbers for a 1963 327/340.
Casting number on both heads are 3782461 as I think they should be.
Both casting numbers have an additional 2 digit number sideways right next to them; one looks like a B7 and the other a B8 (or3).
The GM logo in the center of the head has numbers next to it; the driver's has a 3 and the other has a 4.
Where I would expect the casting numbers there seem to be 2 sets of numbers.
The GM 3 head has what looks like 13 or I3 and E28
The GM 4 head has what looks like 13 or I3 and E33 (this obviously can't be May 33).
Could they both be Jan 3rd? What is the E number?

Any detail explainations for the various numbers that appear in addition to the correct casting numbers would be appreciated.

thanks

Bruce-----


The "E28" is likely actually E23. This would denote May 2, 1963. The "E33" would denote May 3, 1963.

The 3 or 4 next to the "GM" are pattern numbers.

[Mel H.]

Re: 327/340 HP head number(s) clarification please

Here are pics of my 63 340 for reference.. a Jan 21, 1963 assembled car... L212 for Dec 21, 1962... 461 heads... GM4 (think this is line four??) Never linked pics before so hope this comes thru.

100_0728.jpg100_0729.jpg100_0732_00.jpg

[Duke W.]

Re: 327/340 HP head number(s) clarification please

You can't see it with the heads installed, but underneath the water passage you should find an "X".

This is the 461X head and back in the day it was THE "Fuel Injection" head though now the term seems to apply to any 2.02/1.6" inch valve head even though the 461X heads were only manufactured with the 1.94/1.5" valve set.

They have a slightly larger inlet port - somewhere around 170-172 cc versus about 160 for later small block heads including those with 2.02/1.6" valves. They are essentially a cast iron version of the ill-fated 1960 aluminum head.

The 461X was first used on the '61 275 and 315 HP FI engines and these heads were why the power ratings were up from the previous 250 and 290. They were also use on all 300, 340, and 360 HP engines through '63.

Well into the seventies these heads were preferred by some sprint car engine builders. Supposedly, a higher nickel content made the cast iron tougher and more resistant to cracking.

IMO they are the best vintage heads available, but, unfortunately I haven't found any reliable flow numbers for a properly massaged 461X with with the OE valve size, but I'm still looking.

For those engines originally equipped with these heads I DON'T recommend increasing the valve size.

Duke