Re: exhaust cross over (heat riser) fill
 

Correct, I was under the impression as long as it does not protrude into the valve pocket you are OK. Exhaust runner volume still needs to meet minimum spec. Not sure how you would measure it it if was not filled.

Adam good to hear it is worth power.

Scott

Re: exhaust cross over (heat riser) fill
 

If this is all legal I've learned something new.

Re: exhaust cross over (heat riser) fill
 

NHRA pours an outer runner to check cc`s on a Pontiac head.

It`s okay to fill the heat crossover but you can`t do any blending in the exhaust bowl on a Stocker head.

On a bracket head my buddy who does heads for a living will over fill the heat crossover in the exhaust bowl so he can blend all that in when he ports the head. Not legal in Stock.

Re: exhaust cross over (heat riser) fill
 

page xv under "HOW TO USE THIS RULEBOOK" in the rule book


On the other hand, as to performance equipment, it is the
general rule that unless optional performance equipment or
performance-related modification is specifically permitted by
this Rulebook, it is prohibited. All model, engine, or equipment
changes or modifications not specifically addressed in this
Rulebook must be submitted in writing to NHRA for
consideration prior to competition. Approval will be granted or
denied in NHRA’s sole and absolute discretion. The applicant
will be notified of approval or rejection in writing from NHRA
headquarters in Glendora, Calif.


as I read it "Blocking passage down in valve pocket prohibited."I have not seen any where in the book that says "I was under the impression" lol

Re: exhaust cross over (heat riser) fill
 

The bar of zinc alloy is the only way to go. I cut a piece off and heat it in an iron skillet like this http://img2.etsystatic.com/008/0/589...29082_6cdm.jpg with a cutting torch and pour it in, block the intake side and then blend into the bowl if it's not a stocker head.

Re: exhaust cross over (heat riser) fill
 

Considering that all the accepted Edelbrock aluminum heads that I`ve seen have no crossover provision at all, thus no "cave" in the port, wouldn`t it be nice if NHRA allowed factory heads be completely filled too?

Re: exhaust cross over (heat riser) fill
 

Kelly, I do this process for one of the premier shops in the country. You CAN fill and separate the exhaust crossover in the head.In fact, the newer LT1 style head has this feature, unlike earlier SBC heads.
On Stockers, I place a cotton ball, saturated with plaster of paris into the exh. hole from the port side. I push it in about 3/16ths so there is no question about it being in the port.
This does not hurt the flow ,I have been told .I then fill it right up from the intake side, and then grind off excess.
On bracket engines , I fill from the port side ..in one side ,until it comes out the other port, then grind and smooth, as others have stated. It really helps to put about a 1/16 th air bleed hole in your block off plate.
I have been using aluminum and a home made ladle ,and a cutting torch.
I will look into the zinc deal. Thanks

Re: exhaust cross over (heat riser) fill
 

Thanks to all that replied, Ron.

Re: exhaust cross over (heat riser) fill
 

Ron,

You have a PM ........

Re: exhaust cross over (heat riser) fill
 

Adam Strang, you have a pm.