1966 Heads?

[Charles M.]

Here is some info: right side is - GM7 3782461, date A 5 6 left side is - GM16 3890462, date D 11 6. Question is: Can I use them together stock or do they need to be ported, polished, chambered, etc. to be equal internally?

[Frank H.]

Re: 1966 Heads?

I've seen these heads paired together many times on race cars and for sale and thought it would be better to have a matched set,but I've been told that some cars came with one of each and they are considered the same castings for use and paired up by many machine shops.
See if one has been machined,surface milled,or ported or milled .010 if no machine work has been done to either, they should be equal ,if one has had a few valve jobs and the other has not, sinking the valve raises the camber size

[Tom D.]

1966 Heads - See example of 462's

Alan Colvin says both have 62.076 cc chambers, and that ...462 came late in 1966 MODEL YEAR. He also writes "some sources indicate dates before Jan., 1966" for the ...462 heads. "Most applications of the ...461 heads were before January, 1966".




Sample pictures on this web page

[Duke W.]

This brings up an interesting question

Does anyone know what the actual differences between 461s and 462s? The fact that the casting number changed implies that the DESIGN changed, which would mean some meaningful change in the coring, but I haven't got the foggiest idea what it is.

Duke

[Charles M.]

Re: This brings up an interesting question

Duke, one person has suggested to me that the chamber SHAPES are different. Most who have replied agree the chamber vols are the same, 62.076 I think.

[Pete Whelan]

Re: 1966 Heads?

Chuck,
I believe that the spark plug position was moved when the change from 461 to 462 was made. I'd go ahead and measure the combustion chamber volumes in both heads to see if they are within 1 cc of each other. I don't believe that there is a difference in the intake or exhaust port volumes between the two castings. You might want to verify to make sure.

I have sets of both heads and don't recall seeing any other differences.

Pete

[ronnie robertson # 36786]

Colvin's Chevy by the #'s

Says that the 461 and 462 are similar "except for combustion chamber change".

[Charles M.]

Re: Colvin's Chevy by the #'s

I'll send Mr. Colvin an e-mail.

[Tom D.]

No, 3774682 is the one with the chamber change

I think he was referencing a third head (3774682).

[Joe C.]

Re: This brings up an interesting question

Duke:

This excerpt from David Vizard's book on smallblock Chevy heads: "Head casting 462, made from late 1966 through 1968, sported the double hump logo ( same as the 461-Joe 32899). The plug location was a little higher than on the 461 (whose plug location is very near the face of the cylinder head), and the quench area behind the plug was relieved, a style that set the pattern for 186, 041, and other subsequent castings.................. These heads are a good choice to work with..........Numerous large valve versions at 2.02 in. intake and 1.60 in. exhaust were used on 327 Corvettes, but many 1.94 and 1.50 in. valved versions were used for more mundane vehicles."

Joe

[Gene M.]

Re: racer explaination of 461 vs 462

Duke,
I was informed by an old friend ex-stock racer Dale Merz, that the 462 casting has a little less material around the exhaust and intake pockets. Both the 461 and 462 are not recommended to pocket out for hardened valve seats, but the 462 is even thinner. That was his explaination of the differences when I asked.

[William C.]

Re: racer explaination of 461 vs 462

The 462 head has a slight relief at the edge of the chanber to make it more tolerent of carbon buildup on the piston. Otherwise virtually identical to the 461.