Blocking Crossover Passage

[Daddys409Belair]

Hey Guys-

What would you suggest I use to block my pre-heat crossover passage (under the carb) with? I've heard steel-wool from a friend, but it seems to me that wouldn't hold up. I thought one of you might have a better idea, or confirm his suggestion.

It's a cast iron intake, if that helps.

Don't worry - I'm running headers (no heat riser valves!!) :eek:

Thanks in advance.

 

[dq409]

You can use a thin piece of stainless steel and secure it in place with the gasket. Most HiPer intake gaskets now come with that kind of block off.
Or fill it will alum,,dq

 

[Tom Kochtanek]

Aluminum

I went with a simple aluminum fabbed piece, used it on the aluminum 2 four intake, seemed right . I don't think steel wool is the answer, but who knows? .

Good luck!

TomK

 

[Fathead Racing]

Tom, I think the aluminum would not hold up in that hostile enviroment. Stainless steel is the way to go IMO. That is what I have used with reliable results.

 

[tripowerguy]

I have used stainless steel for years and when you tear down the engine the piece is like new. I would believe aluminum would erode given how thin it has to be. Roy

 

[Tom Kochtanek]

Makes sense!

I better check my handy work, may have made a mistake. Thinking about this, it makes more sense to go with stainless. I will check mine and correct if need be!

Best,
TomK

 

[dunhamfield]

OK, what am I missing? What is the purpose in blocking this passage?
I see that there are holes coming into the carb gasket area from these passages.
Is this a problem if mounting a Holley carb?
Couldnt you just tap the hole and install a plug?
Be gentle guys, I just learning these beasts....

 

[Impalaguru]

I've used steel wool stuffed into the heat passages in the carb pad with great results. Its been in there for many years. I'm running an AFB. Without those holes blocked the AFB will soak up the heat from an iron manifold resulting in instant boiling fuel.

I've also used a bakelite insulator and stainless shim from a 300hp 327 with equal results. With this set up you can keep the heat passages if you want. Corvette parts places have these.

Ross

 

[models916]

block it off

Blocking the passage assures that no exhaust gas travels thru the manifold and heats the fuel charge up. Daily driver in cold climate, ok. it works. Performance ride, Block it off. You need to make sure the thermal valve in the exhaust is locked open or removed. Headers? just block the passage in the manifold.

 

[Mr Goodwrench]

I have a melting furnace and usually block one side off and pour molten aluminum in the other side to fill it up. I also tap the two holes that come up to the carb base and install 1/4" pipe plugs prior to pouring. I never had any luck with the thin shims to block off. seem no matter how thin they always held the intake up in the middle causing poor sealing everywhere else.

 

[Rockfish39]

Molten Aluminum

DQ and Goodwrench have the right idea!!!!!! FILL the port with molten aluminum. There are several real good reasons why I use this method

1. Aluminum dissipates heat efficiently. The physics work well under the intake plenum because it actually serves to regulate the rate and amount you are heating up the surrounding cast iron at the bottom of the plenum. Read an interesting article called "the copper cooled Chevrolet" A simple internet search will get you there. It's a fascinating look at early, early (circa 1915) attempts at non-water based cooling techniques in Chevy engines.

2. Since Chevy intakes have water passages and a thermostat, total temperature stability is acheived in about 5 minutes

3. Carb tuning and optimization can now be a painless process

4. Keeps the exhaust from COOKING the paint that is on the intake, which is handy if you want to be "show ready"

Rock

 

[Mr Goodwrench]

If anyone would like this done I would be happy to do it at no charge if you ship me the manifold, which is not cheap.

 

[tripowerguy]

You know Goodwrench another advantage of pouring molten aluminum to block passage would be to clean up that port. I ported my heads and that was the place I thought really could be improved upon. Do you take a grinder and contour the port after plugging the crossover? Roy

 

[Mr Goodwrench]

roy are you talking about the intake??? or the heads??? I have seen the crossover ports in the heads filled and then contured, but always fill the Intake no grinding.