exhaust cross over (heat riser) fill

[Tom Goldman]

It's a good idea to pre heat the cylinder head before pouring the aluminum filler.
otherwise the fill chills too quickly and can shrink around the outside. also make sure you melt enough to do it in one pour.
I fill from the intake side,blocking the port side with a little furnace cement and a steel plate securely blocked in place.
You dont want that come out while you're filling! ...unless you like shiney silver shoes!!

[FSA1673]

Originally Posted by 442OLDS

You race F/SA?

Yes, run in E and F, mostly local combo events. 1971 Pontiac T-37 455/335 hp combo.

Thanks, Scott

Mark,

Yes headers should work as designed just not sure it will actually turn into more power and lower et?

[dartman]

Originally Posted by FSA1673

Mine have been filled with aluminum, poured in from the combustion chamber. I used to just have them blocked off with aluminum plates on the intake side of the head. My 71 HO intake is aluminum and does not have the heat cross over as part of the intake.

I am curious if filling the head with aluminum will result in any power gains now that the two middle cylinders are not connected anymore.

Any thoughts??

Scott

Heat riser passage may be
blocked from intake manifold side of cylinder head. Blocking
passage down in valve pocket prohibited.

I use thick tin between my intake gasket and head as i was told by the tech guy that pouring in is prohibited

[Adam Strang]

As I said before I pour from the intake side and use steel wool to block the passages in the exhaust runner.

I have dynoed it both ways and did see a difference.

It also gets rid of the dead skip sound Pontiac`s have with open headers.

[FSA1673]

Originally Posted by dartman

Heat riser passage may be
blocked from intake manifold side of cylinder head. Blocking
passage down in valve pocket prohibited.

I use thick tin between my intake gasket and head as i was told by the tech guy that pouring in is prohibited

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

[kansas stocker]

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

[Adam Strang]

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.

[dartman]

Originally Posted by FSA1673

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

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

[Mark Yacavone]

Originally Posted by dartman

Heat riser passage may be
blocked from intake manifold side of cylinder head. Blocking
passage down in valve pocket prohibited.

I use thick tin between my intake gasket and head as i was told by the tech guy that pouring in is prohibited

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

[R. Thorne]

Thanks to all that replied, Ron.