[Leftyarmstrong]

So I buy this stock intake that has an afb carb on it. There are two small tubes that go from little holes in the crossover to the choke and to an area just on the rim of the air intake on the carb. Until I get that afb rebuilt, I put my Edlebrock on there just to get it running. Well, there's exhaust coming out of those holes and I'm wondering what the heck I'm going to do with those if I don't use those little tubes (thinking about using an electric choke) or those little tubes don't really seal in those holes. And what's up with that one dumping exhaust into the carb? I really wanted to block off that crossover but I didn't see an easy way to do that. How do I work my way out of this?

[Tom Vaught]

There is supposed to be a "heating loop" below the flange (inside the heat riser portion of the intake. On a Tri-Power engine you can remove the flange bolts and clearly see the tube (and remove the "tube/ flange assembly".

Have not taken apart a AFB 4 bbl intake in years but suspect that they have the same kind of deal. If the flange was missing the "tube loop" then exhaust could come out of the flange openings.

The way that it is supposed to work is:

1) Clean Fresh Air from the air cleaner goes through a metal tube to the flange on the intake cross-over.

2) The Clean Fresh Air goes through the heated loop in the intake. From the flange outlet, the heated air goes to the choke housing where it heats up the choke spring.

3) There is a passage in the carb (under the choke housing) that draws the fresh air through the "heating system" from the air cleaner location.

This gives you fast "choke come off times" so that the engine does not run rich with the choke on for long periods of time.

Tom Vaught

[dld]

Years ago the gasket manf. made gaskets with a block off plate that would cover the port from the head . This would stop the exhaust and HEAT from going into the manifold and heating the carb. You could use this set up with a elect choke. But living in SURF CITY
USA......... you may not need a choke at all.

[geeteeohguy]

I think those gaskets are still available. I saw an ad for them recently, I just can't remember where. For track use only, on non pollution controlled cars. I've seen thin sheet metal plates used, too.

[Dick Boneske]

Our host and others sell a "U" shaped replacement choke heater that is not very difficult to install. It requires the manifold be off the car, drilling out the old burned-thru tubes, and installing the new ones by swedging them with a large center punch until the external choke heater tubes fit the holes.

Any fix you are contemplating will require manifold removal except plugging the two holes so exhaust can't leak.

[Leftyarmstrong]

Thanks guys. Turns out it wasn't the heat tube. It was the gasket itself that was leaking at the top of the port on the passenger side right where that tube loop is. I laid the manifold on those heads without the gasket and the fitment looked dead nuts. With the motor on a stand I took my time laying up the gaskets using the orange retainers and carefully set the intake. I used brand new bolts and AN washers and torked it down in a carefully orchistrated star pattern, settling on 45 ft lbs. It leaked. Pulled the intake and it looked good everywhere except right at the top of the exhaust port on passenger side. I could see the carbon where it was leaking. Been advised to reinstall using red hi temp silicone but I'd really like to block that crossover (I'd use an electric choke) so if anyone knows the trick gasket let me know. Thanks, Don

[Dick Boneske]

You don't need special gaskets to block the heat riser passage. Get two pieces of 16 gage stainless steel (about .060" thick) cut to about 2"X 2" and put them over the holes in the heads with a little hi-temp gasket sealer. Install the gaskets and manifold normally with a little hi-temp sealer over the top of the stainless plates, too.

I use gasket sealer only over the water passages on both ends of the heads. The rest of the gasket (over the ports) needs no sealer.

[Leftyarmstrong]

I'll look closer at it tomorrow but let me ask you, how does the stainless block plate lay in there? Does it lay inside the port on the head or is there room for it to lay up on top of the gasket and still get the intake to seat? I can certainly fabricate what you are describing but I just need to know how it fits in there. Thanks, Don

[Dick Boneske]

Put some hi-temp sealer on the plate. Lay it on top of the cylinder head, covering the heat riser hole on each head. Put some more hi-temp sealer on the top side of the plate. Install the manifold as you normally would. The plate is sandwiched between the intake gasket and the cylinder head. The thin (16 gage) will not interfere with fit.

[Leftyarmstrong]

I get it now. Thanks for that info amigo. And to all the other hombres that helped me out of another jam.

[FFD]

Thats a Mr. Gasket gasket with the pates already in the gasket. If you need a new manifold gasket the gaskets are side by side in the parts book if your ordering from a parts store