461 heads for my 65 vette

[brumbach]

I'm gathering the components to build the correct engine for my vette (327/350). Purchased the block a couple of months ago and now looking for heads. I've found a set for sale. They're remanufactured with the following description of work. Will these be okay for my project?

Completely rebuilt SBC double hump heads. These are 461 heads with approximately 60cc combustion chambers. They have been fitted with, 2.02 intake & 1.60 exhaust, one piece stainless steel valves, hardened seats and 3/8ths screw in studs and guide plates. Solid bronze guides, the brodix type, were installed along with 110 lb springs and pc valve seals; the bowls were ported and blended nicely. These heads will flow very well. Also included is a new set of stamped steel long slot rocker arms 1.5 ratio.

 

[JohnZ]

Sounds good, but it doesn't indicate whether the heads were originally fitted with the 2.02/1.60 valves or whether they were converted later from heads that originally had 1.94/1.50 valves. The factory took an extra cut on the intake valve side of the chamber on heads factory-fitted with 2.02 valves to unshroud the chamber in that area for improved airflow. If 1.94 heads are converted later to 2.02's and the unshrouding cut isn't made, they'll flow less air with the 2.02's than they did with the original 1.94's. Photo below of the factory unshrouding cut on 461 heads.

 

[brumbach]

John, forgive me for a dumb question (I'm a layman at best) but if the unshrouding cut wasn't made and the conversion was, then the loss of air flow you mention would mean less compression and therefore reduced performance, right? If I understand correctly, then would this be a signficant reduction in performance (from the intended 327/350)? Thanks

Sounds good, but it doesn't indicate whether the heads were originally fitted with the 2.02/1.60 valves or whether they were converted later from heads that originally had 1.94/1.50 valves. The factory took an extra cut on the intake valve side of the chamber on heads factory-fitted with 2.02 valves to unshroud the chamber in that area for improved airflow. If 1.94 heads are converted later to 2.02's and the unshrouding cut isn't made, they'll flow less air with the 2.02's than they did with the original 1.94's. Photo below of the factory unshrouding cut on 461 heads.

 

[JohnZ]

John, forgive me for a dumb question (I'm a layman at best) but if the unshrouding cut wasn't made and the conversion was, then the loss of air flow you mention would mean less compression and therefore reduced performance, right? If I understand correctly, then would this be a signficant reduction in performance (from the intended 327/350)? Thanks

Not a dumb question at all. Won't bother compression at all if the cut isn't made, but the engine won't pump as much air at high rpm as it did before, so wide-open throttle/high-rpm performance will be slightly less than before the conversion. The unshrouding cut is necessary to take advantage of the increased valve diameter. Chevrolet wouldn't have spent the money to rearrange the head line and add another dedicated machining station just for 2.02 heads if it wasn't necessary, and old editions of the Chevrolet Power Manual show prints with the detailed design of the cutting tool required to duplicate the cut when doing the 1.94-to-2.02 conversion.

 

[Fuelie]

John is 100% right as usual.

There is a very good possibilty that since the heads have also had the bowls blended, that the shop that did them might have been smart enough to un-shroud the intakes while they were doing the conversion.

Try and get a couple of digital shot of the chambers before you make a purchase.

Take care,
Brian

 

[brumbach]

Here is a picture of the heads. Don't know if you can tell much with the valves installed. Another question, if the heads were originally equipped with these valves, would there be a unshouding cut?

(hopefully I've done the attachment correctly)

 

[Fuelie]

It is very hard to tell in the photo if the chambers have been "cut" to unshroud the intakes.

Yes, if these heads were originally equipped with 2.02" intakes the chambers would have been cut just as is shown in John's photo.

Take care,
Brian

 

[brumbach]

Please look at this picture and give me your opinion regarding proper unshrouding. He responded to my inquiry by stating the below.

I assume you are referring to the combustion chamber, and yes it has. We scribe the heads for a 4.030 bore and cut all the way out to that line with a radiused chamber cutter.

 

[JohnZ]

Yup, looks like the unshrouding cut has been made - it's just not as deep as the factory cut and isn't as apparent from the straight-on view.

 

[brumbach]

One last question --

The seller states "The valve job is a 3 angle competition valve job". Is this good or bad for my application?

Thanks,

Bill

 

[JohnZ]

That's good - should be considered as mandatory for any rebuild these days; almost every good machine shop that does head work has a Serdi machine that does it in one pass per hole.