Carter AFB insulator plate

[KongaMan]

I have a couple of questions about the metal plate that was used between the carb body and the mounting gasket on the AFB's ca. 1964:

- Were these plates made of aluminum or stainless?

- How thick is the plate?

- Anyone have a picture of one?

Thanks.

[RivNut]

Dear ?????????

They were made of stainless, the exhaust gases corroded the aluminum base of the carburetor, therefore an aluminum heat shield would not have worked.

Here's the email address of a guy in the Detroit area who

is reproducing them - rocking-b@comcast.net.

His name is Paul; when you contact him, tell him "Ed says, Hey." The shields that he's producing are just a little thicker than the original, hence they'll offer more protection.

When you replace it, it goes between the carb and the fiber gasket. Its purpose is to warm the base of the carburetor so the carb will run better in cold climate conditions by helping to vaporize the fuel. If it's not in contact with the base of the carb, it is useless.

Ed

[Jim Cannon]

Ed is correct, the plate must touch the base of the carb to warm it. If warming the carb throttle body is important to you (to prevent carburetor ice, caused when you drive in cool, damp conditions) make it touch the carb base.

If it does not touch base of carb, though, at least it keeps exhaust gases out of your fuel intake stream (which makes it run really poorly -- guess how I know!). As soon as I replaced my plate (previous owner tossed away) it started to run correctly again.

[KongaMan]

Thanks for the info. I'll pester Paul and see what he says.

[alex bonino]

After reading this thread, I'm now wondering if I have one (carb plate) in place. Is it obvious upon visual inspection that the plate is there? ie, can you see the thickness of the plate between the carb base and the gasket and manifold?

alex

[KongaMan]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RivNut</div><div class="ubbcode-body">If it's not in contact with the base of the carb, it is useless.</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jim_Cannon</div><div class="ubbcode-body">Ed is correct, the plate must touch the base of the carb to warm it. If warming the carb throttle body is important to you (to prevent carburetor ice, caused when you drive in cool, damp conditions) make it touch the carb base.</div></div>

FWIW, this is what Paul had to say about installing the plate:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...require a gasket on both sides due to the thickness of the shield. </div></div>

[RivNut]

Then don't buy that shield. If the aluminum doesn't touch the base of the carb, there's no heat transfer. You might as well plug up the passages and use just the fiber gasket. If you want to use a stainless gasket and retain the function of heating the carb for cold weather conditions, contact Allstate Carburetor and Fuel Injection in Central Islip, NY (631) 234-8327. Very knowlegable and customer oriented.

Ed

[Ted "Wildcat65" Nagel]

Carmen Faso sells a replacement for these-

He is a long time ROA vendor, see J & C's parts add!

He is @ 716-693-4090

I've bought a stack of them from him.

[NTX5467]

Whoops! Let's make sure that Paul is talking about what WE are talking about, not to mention "terminiology" too.

On the earlier GM V-8 intake manifolds which had the "heat track" at the front of the carb mounting pad, which brought heat from the exhaust crossover area to the primary side of the carb for better driveability in cooler weather, it was a TWO-Piece gasket . . . the fiber gasket touched the intake manifold and the STAINLESS STEEL "shim" gasket went between the carb base and the fiber gasket. Conventional wisdom would dictate that a fiber gasket would be needed on both sides of the stainless steel shim gasket, but that's not the case. The vehicles came from GM with no gasket between the stainless steel shim and the base of the carb--whether it was a Chevy V-8 or a Buick V-8.

As for the "aluminum shield", that sounds more like the "heat shield" used in the early 1970s on some Chevy V-8s (available initially from GM Parts and later from Holley). It was a thick piece of flat aluminum which DID need a fiber gasket on the bottom AND top of the shield for it to work. This was before the thicker heat insulator gaskets came into wide use--paper-style gaskets, thick, which had plastic sleeves so you would not compress the gasket unevenly when you torqued the carb down to the manifold. This is NOT the same type of gasket or situation as the OEM carb base gasket as used with the heat track intake manifolds.

The intake manifolds with the heat track had a unique shape for the fiber gaskets at the front of the carb. A normal gasket (later model usage for intakes without the heat track feature) will not work with the earlier manifolds--it will not adequately seal the heat track area and an exhaust leak will result--even if the bolt pattern of the gasket is the same.

I believe that if you spray some carb cleaner on the base gasket with the stailess steel shim gasket, you'll be able to see each "layer" of the gasket--the fiber gasket on the bottom and the stainless steel piece between that and the carb base. Seems like there was a tang on the stainless steel item that stuck out near the driver's side throttle linkage?

So, with all due respect, it appears that Paul is referencing the aluminum heat "shield" insulator/gaskets of the early 1970s, which were NOT OEM production with GM vehicles. They were initially in the GM Parts book for Chevrolets, with Holley carbs and Q-Jet spreadbore carbs . . . if you knew how to read the book . . . and later in the Holley carb catalogs. These "insulator" items were supposed to function as a "heat shield" for the carb and nothing more.

Regards,

NTX5467

[KongaMan]

Because I can, a pic of an old nailhead carb gasket:

This particular gasket is all fiber. You can clearly see the passage around the primaries. I also have an old gasket that is fiber on one side and dimpled steel on the other. However, it also has the passage around the primaries.

The goal here is to provide the warming capabilities without getting carbon into the carb. It would seem that a gasket with the passage would permit warming by means of convection, with the hot exhaust gases coming in direct contact with the carb body (at the cost of carbon buildup). Conversely, a plate without the passage would warm the carb through conduction: the gases heat the plate, and the heat is transfered from the plate to the carb through contact. This would seem to imply that a fiber gasket between the plate and the carb would severely limit (if not altogether eliminate) the heat transfer.

And that gets to the question: Was there a stock shield that did not have the passage - one that prevented manifold gases from actually getting into the carb?

[Guest Riviera66]

Gosh... it warms the heart (and carburetor) of a Tech Advisor to see several guys all correctly discussing the purpose of the plate and how it needs to be positioned to work. I would only add that if you don't have the plate in at all, the car will run horrible... not just at a cost of carbon buildup. I can also add that for it to work as effectively as it was designed, the heat riser valve would have to be functional (though some exhaust heating would still occur) even without it.

I'm not sure what the last question means... the metal plate (used up through '67) doesn't allow direct contact of gases to the carb...

Darwin Falk

1966-70 ROA Technical Advisor

[RivNut]

The fiber shield is as pictured and it is used in conjunction with the stainless heat sheild; it allowed the warm exhaust gases to reach the stainless heat shield, but not touch the body of the carburetor. I don't have it know, it was junk so I threw it away, but perhaps someone out there still has one they could post a picture of. I'm speaking of an AFB carburetor where the heat shield had been discarded and the aluminum has been exposed to the exhaust gases. Big corrosion, most of the entire base of the carb was gone. That's why the shield is there, to protect the aluminum body of the carburetor from the exhaust. You need both, the fiber gasket for sealing, and the stainless shield for protection.

For those of you (and me on one of my 63's) who had/have a car that came equipped with a Rochester 4GC, you'll notice there is only the fiber gasket with the same cutout around the primaries, but there is no stainless piece. The reason is simple; the Rochester carb has a steel base plate. It isn't affected by the corrosive properties of the exhaust.

Don't mess with what Buick knew would be a problem. If you run an AFB on a stock unplugged intake manifold, you need the stainless shield next to the body of the carb; it provides heat via contact (and the cutout in the fiber gasket allows the gasses to reach it,) but it also provides protection from corrosive gasses. Don't take any chances.

Ed

[KongaMan]

For general edification, I'll bump this with pictures of the parts in question.

Gasket:

Carmen Faso's plate (.017" thick):

[RivNut]

I'm a friend of Paul's and he's a nice guy, but in my opinion he tried to make a good thing better, gotta' love the enthusiasm. He made the new shield too thick, thinking it would be an improvement. But, in doing so, it's too thick to seal properly so he says you need to sandwich it between to fiber gaskets. Doing this defeats the purpose of having the steel next to the carb body for heat transfer. (I don't think Paul truly understands the reason for the shield.)

Go with the one from Carmen or try Allstate Carb and Fuel injection in Long Islip, NY.

Ed

[petelempert]

This whole insulater double gasket thing was new to me. In fact, I just rebuilt the Carter on my 63 (car came without the aluminum plate and or the correct "heat crescent" die-cut fiber gasket so I didn't know what I was missing) and it ran pretty badly until it was really warm. I read this thread and bought the right gasket and plate from the Islip vendor. WOW...what a difference it makes at initial start-up. Thanks to all you guys. PRL