C2 "461" vs. "462" heads

[Justin N.]

Dear Members,

I recently purchased a set of heads for my 67 coupe. One has the 461 casting and the other is a 462. Aren't these the same heads, but different years? Both have the original GM valves and appear to be similar, but my machinist said the combustion chambers looked different. I thought they all had the same 64cc chambers. Need help please! Thank you!

Justin #41362

[William C.]

Re: C2 "461" vs. "462" heads

The "462" head has a carbon relief built into the edge of the chamber, and I believe a slightly larger volume.

[David N.]

Re: C2 "461" vs. "462" heads

Justin, My Corvette Black Book by Mike Antonick shows the "461" head for a '61 thru '66 small block. The "462" is from a '67 300 or 350 hp 327 cid. Not being a mid-year expert, I don't know if they had different size combustion chambers.

Good luck,
David Nims #19639

[Tom D.]

Lots in archives about this, I think *NM*

[Charles M.]

Re: C2 "461" vs. "462" heads

Jutin

I have the same two heads as you on my non-original 327 in my 64 with a 66 engine. Bill is correct. There is a slightly cut out area (I can't remember which head) along one edge of the combustion chamber. I have my heads off right now. It causes about a 2cc difference in volume. Other than that I believe the heads are identical. I never knew what the difference was for. Bill can you explain what the "carbon relief" area is for?

Chuck

[Duke W.]

Re: C2 "461" vs. "462" heads

The 461s have a narrow quench zone on the spark plug side of the chamber. On the 462s this area is beveled back to the edge of the cylinder bore with a slightly different mold pattern, which eliminates this small quench zone and adds about 2-3 cc to the chamber, and I believe the 186 production and 492 service castings include the 462 chamber features.

I recall from previous discussions that the 462 spark plug location may be a little higher than on 461s.

Also, if the castings were orignally machined for the 2.02" inlet valves there should be a radius cut of about 2.34" - 2.40" (may have varied slightly over the years) centered on the inlet valve guide to unshroud the valve.

Duke

Duke

[Brian Monticello]

Re: C2 "461" vs. "462" heads

A picture (or two) is worth a thousand words. Picture below is of a 462 cobustion chamber and the picture at the link below is a 461 combustion chamber.

The extra volume on the plug side is obvious and the plug is higher up in the chamber. Note the 462 example has an unshrouded intake valve and some bowl work done. The 461 example is untouched. 461 is 2.02/1.6 and the 462 is 2.02/1.5

brian