SS Head Porting Rules ?

[oldskool]

Copied this from a 2014 rule book.

"...Porting, polishing, welding,
epoxying, and acid-porting permitted. Grinding and polishing in
combustion chamber permitted..."

I know absolutely nothing about SS head porting.

Just by what I read in the rule book, I ASSUMED that most any mild street porting job would be legal, in SS.

BUT, a guy on another forum suggested that ANYTHING that increases the volume of a stock factory port is illegal. I mean, even just a mild gasket match will increase port volume.

I was just trying to figure what kind of head work it would take to build a low buck Pontiac SS engine, that would have just enuff power to run the index, or just slightly quicker.

There are several Pontiac shops which offer mild street porting jobs which increase flow enuff to make the required power.

So, for you guys who know, is mild porting illegal, even just a gasket match, if it increases the volume of a single port, even a little ?

I mean, the acid ported Stocker heads have larger than Stock volume ports, don't they ?

Need some technical clarification on what is & is not legal for SS heads.

Thanks !

[Mike Pearson]

It just has to meet the published port volume in Cc’s for the head number that you are running. Both intake, exhaust and combustion chamber. If they are big after poring then you fill back in with weld or epoxy to get back to the correct port volume

[oldskool]

Wow ! So even a very mild gasket match would be illegal in SS, unless you added weld or epoxy to offset any material removed ?

So, is all the high dollar head work done just to change the SHAPE of the ports, rather the the size/volume ?

Or do the techs just sorta let it slide, like they must have been doing all these years for the acid ported Stocker heads. I assume that everybody knows those big power, 8000rpm Stocker heads, couldn't possibly flow that much, with completely untouched factory ports.

[Mark Ugrich]

Look up the allowed combustion chamber and intake and exhaust runner volumes in the classification guide for the Pontiac engine you want to use. Then compare the volumes to what the head has in unmodified form.

[oldskool]

So, those port volume limits are exactly the same for both stock & SS ?

[Mark Ugrich]

No, porting is not allowed in stock eliminator. You need to find the volumes allowed in super stock for your particular cylinder head.

[72 goat]

My experience with late model (7K3, 4X) heads is that from the factory the port size is smaller than the maximum allowed, and the chamber is larger than the minimum allowed. My (non professional) experience is that the heads can be milled to get to minimum cc's, and that bowl work can really improve flow.

[Alan Nyhus]

Register to Dwight's site and you can find the accepted port volumes on anything that's in the NHRA books. It also shows the rest of the engine specs and classification.

The yellow highlighted area on the rt. is slick as it shows the different cars a specific engine came in. -Al

http://www.classracerinfo.com

[Jim Hanig]

Originally Posted by oldskool

Wow ! So even a very mild gasket match would be illegal in SS, unless you added weld or epoxy to offset any material removed ?

So, is all the high dollar head work done just to change the SHAPE of the ports, rather the the size/volume ?

Or do the techs just sorta let it slide, like they must have been doing all these years for the acid ported Stocker heads. I assume that everybody knows those big power, 8000rpm Stocker heads, couldn't possibly flow that much, with completely untouched factory ports.

Generally the heads are smaller than the leagle size. Gasket match and short turn you should stay with in the list. Unless the heads have been acid ported.

[Ed Wright]

Generally, after milling the heads to correct chamber CCs, the intake side requires milling so the manifold fits correctly. That takes a few CCs off the intake runners. Decking the block (sbc engines here) needs the same.
We gotta put those CCs back, right? :-)