exhaust cross over (heat riser) fill
 

Anybody use the Resbond products (907gf, 940, 940ht) to fill them or does everybody just melt aluminum and pour? Any other high temp epoxy used? Pontiac v8 application. Thanks, Ron.

Re: exhaust cross over (heat riser) fill
 

Aluminum and I pour from the intake side.

Re: exhaust cross over (heat riser) fill
 

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

Re: exhaust cross over (heat riser) fill
 

Scott, You've got to figure that now you are using a true 4-tube header .. FWIW

Re: exhaust cross over (heat riser) fill
 

You race F/SA?

Re: exhaust cross over (heat riser) fill
 

Ron,
I use zinc alloy get from Mc Master Carr supply ,it's the same thing Mondello use to sell.
I melt enough into a steel cup I made from tubing and flat bar w/flat bar long enough to also be handle to pick up and pour with,I usaully block @ intake side and pour from bowl side have to use some sort of funnel some times.
The zinc will probaly out last the heads.
Mike Taylor 3601

Re: exhaust cross over (heat riser) fill
 

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!!

Re: exhaust cross over (heat riser) fill
 

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?

Re: exhaust cross over (heat riser) fill
 

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

Re: exhaust cross over (heat riser) fill
 

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.

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.

Re: exhaust cross over (heat riser) fill
 

Sorry to bring up an old thread but I was wondering how much zinc you needed to do this procedure?

This is what I found on McMaster-Carr's website:

http://www.mcmaster.com/#zinc-alloys/=outleo

Great info guys! Thank you

Re: exhaust cross over (heat riser) fill
 

I usaully buy the 4 1/2 lbs. bar 9069K2. depending on what type of heads you are working sbc can do 2-3 sets.
Have also filled intakes that are cracked in heat cross over area,just fill it up does'nt matter then.
Mike Taylor 3601

Re: exhaust cross over (heat riser) fill
 

Interesting... I used the exact same Zinc material/part # from McMaster (9069K2) and when I pulled the heads after about 50 passes, I found the material melted back pretty bad in the port area.

Granted, I know it says it melts at 792°F, but I saw others using it with success, and figured there would be enough heat transfer into the head casting to keep it from melting...

Was going to use Aluminum next time (melting point ~1,220°F)....

No one else has melted the Zinc ???

Re: exhaust cross over (heat riser) fill
 

Thank you for the information

Re: exhaust cross over (heat riser) fill
 

I have'nt had any problems that I know of with it melting out of head,I will tearing into one that was done about 200 passes ago will let you know how it looks.

I wonder how consistent melting point is? I have noticed some of the bars seem to melt easier,but I could just be less patient that day.
Mike Taylor 3601