'66 small block heads

[Rob A.]

I'm looking at a '66 350HP car I'm interested in. I see the "double-hump" casting on the heads. Were the same heads used on '66 300HP and '66 350HP engines?

[Mike Cobine]

Re: '66 small block heads

Yes. 3782461, all 327, 1966.

Same ones were used on a lot of years, different only by date code.

[Gary B.]

3890462 heads are correct for late '66 L79 cars

Rob,

The original heads on my July 20, 1966 build date L79 (350HP) are castings 3890462, not the 461 heads. I don't know when the switchover was made, but the 462 heads are correct for late '66 build date cars.

Gary

[Mike M.]

Re: '66 small block heads

Rob,
Casting numbers for the heads were the same, but the valve sizes were different. 300hp used 1.94" intake and 1.5" exhaust, 350hp used 2.02" intake and 1.6" exhaust. The combustion chamber on the big valve head also received an extra cut to "unshroud" the intake valve; see recent postings by Duke for more details.
Mike

[Rob A.]

Re: '66 small block heads

It sounds like even with the valve covers off and the casting#s visible, I won't be able to tell if they are correct for 350HP, am I correct?

[Gary B.]

Rob; Yes, I think you can't tell. *NM*

[Frank H.]

Re: '66 small block heads

Rob
I think the large valve version heads also got screw in rocker studs and pushrod guide plates for solid lifters use,that you would see with the valve covers off.I would be more concerned about the block stamp,the heads can be changed or machined.
FH

[Frank H.]

Re: '66 small block heads

Rob
I think the large valve version heads also got screw in rocker studs and pushrod guide plates for solid lifters use,that you would see with the valve covers off.I would be more concerned about the block stamp,the heads can be changed or machined.
FH