66 base motor carb gaskets sequence...

[Kevin N.]

hey guys...i have a 66 base motor (300hp) with a holley and cast iron intake. all correct of course. when i pulled the carb off i kept all the gaskets in the order that they were installed. they went as follows...intake, thin gasket, baffle plate (thin metal), the insulater spacer (thicker gasket) and finally the carb. according to all my books i am finding that not only is this sequence wrong, but it is only listed for the 63-65 AFB carb. i struck out looking in my assembly manual. all the parts catalogs have it listed this way...intake, thin gasket, insulater spacer (thicker gasket), baffle plate (thin metal) and then the carb. but, again it's only for the 63-65 AFB carb. the catalogs list only the thin base gasket for the 66 base motor with a holley. do i need ALL the gaskets listed in the catalogs for the 63-65 afb carb like mine had when i pulled it apart or just the 1 base gasket? which ones does my 66 actually need? please help and thanks in advance.

[John H.]

Re: 66 base motor carb gaskets sequence...

hey guys...i have a 66 base motor (300hp) with a holley and cast iron intake. all correct of course. when i pulled the carb off i kept all the gaskets in the order that they were installed. they went as follows...intake, thin gasket, baffle plate (thin metal), the insulater spacer (thicker gasket) and finally the carb. according to all my books i am finding that not only is this sequence wrong, but it is only listed for the 63-65 AFB carb. i struck out looking in my assembly manual. all the parts catalogs have it listed this way...intake, thin gasket, insulater spacer (thicker gasket), baffle plate (thin metal) and then the carb. but, again it's only for the 63-65 AFB carb. the catalogs list only the thin base gasket for the 66 base motor with a holley. do i need ALL the gaskets listed in the catalogs for the 63-65 afb carb like mine had when i pulled it apart or just the 1 base gasket? which ones does my 66 actually need? please help and thanks in advance.

Kevin -

The sequence is intake manifold, gasket, stainless baffle, carburetor, as shown in your Assembly Manual (UPC 6, sheet C2, items #10 and #11).

Have you plugged the holes at the ends of the "hot-slot"?

[Russ S.]

Re: 66 base motor carb gaskets sequence...

John, Why do you plug the holes? Wouldn't that cause the choke to work improperly?

[Joe L.]

Re: 66 base motor carb gaskets sequence...

John, Why do you plug the holes? Wouldn't that cause the choke to work improperly?

Russ-----


The choke operation has absolutely nothing to do with the heat slot. Plugging the heat slot avoids damage to the carburetor by exhaust heat. It also avoids more frequent need for carburetor rebuild.

There is virtually no downside to plugging the slot. There might be a little slower warm-up in really cold weather periods but you probably don't drive your car then, anyway.

[Russ S.]

Re: 66 base motor carb gaskets sequence...

Joe, Thank you very much for the answer. What then was GMs reason for putting them in there?

[Russ S.]

Re: 66 base motor carb gaskets sequence...

Another question. What do you have to do to plug them? Drill out to any peticular size or is the current size ok for a plug?

[Clem Z.]

Re: 66 base motor carb gaskets sequence...

when GM carbs had cast iron throttle plates they had a heat slot in the throttle plate fed by those holes and they kept them for a while after going to aluminum base carbs. they then found out this heat slot was not needed for warn up with the aluminum base carbs and they did away with it. a lot of aluminum based carbs were ruined by the exhaust heat because owners used the gaskets improperly

[Joe L.]

Re: 66 base motor carb gaskets sequence...

Another question. What do you have to do to plug them? Drill out to any peticular size or is the current size ok for a plug?

Russ------


There's no need to drill out the holes. Available soft plugs as seen in John's photo can be used to plug the holes. I've forgotten the size but it's one of the commonly available sizes.

By the way, the last year that GM used the heat slot was 1969. It was abandoned thereafter. It was one of the worst ideas they ever had and, finally, they realized that.

[Gerard F.]

Re: 66 base motor carb gaskets sequence...

Russ------


There's no need to drill out the holes. Available soft plugs as seen in John's photo can be used to plug the holes. I've forgotten the size but it's one of the commonly available sizes.

By the way, the last year that GM used the heat slot was 1969. It was abandoned thereafter. It was one of the worst ideas they ever had and, finally, they realized that.

Kevin, Russ,

The plugs I used for my 67 CI manifold were 7/16'" freeze plugs. I set them with a 7/16" bolt. Don't push them too far in, they might drop into the intake manifold.

Here's a pic of them with the driving bolt:

[Ronald L.]

Re: 66 base motor carb gaskets sequence...

If you want a sure way to do this so they never fall out, tap the hole for a NC thread and use a set screw. That's what our threads on the subject last year indicated.

That way you don't have to worry about going too far and if you ever did want to take them out, little effort is required.

[Kevin N.]

Re: 66 base motor carb gaskets sequence...

thanks again for ALL the info guys. i rechecked the assembly manual, again, and did find the page that says it all. i will take it ALL back apart and check for those holes being plugged...
one more note...mr. zahrobsky...that's one mighty impressive resume. most guys would kill just to own 1 corvette let alone 11 brand new ones. i, myself, am on #39, but have never owned a new one, yet!

[John H.]

Re: 66 base motor carb gaskets sequence...

By the way, the last year that GM used the heat slot was 1969. It was abandoned thereafter. It was one of the worst ideas they ever had and, finally, they realized that.

That "hot-slot" design also culminated in the second-largest Chevrolet safety recall since the V-8 motormount failure issue; iron-intake hot-slot cars with Quadrajet carburetors had the bowl plugs fall out, resulting in engine fires. I was in the middle of that one, and remember it well.

[Clem Z.]

Re: 66 base motor carb gaskets sequence...

That "hot-slot" design also culminated in the second-largest Chevrolet safety recall since the V-8 motormount failure issue; iron-intake hot-slot cars with Quadrajet carburetors had the bowl plugs fall out, resulting in engine fires. I was in the middle of that one, and remember it well.

i remember following a olds 98 down the interstate and all of a sudden i see smoke and flames coming out from under the car. i got the car to pull over and by that time the car was on fire. the people got out and i left before things really got bad.

[Joe L.]

Re: 66 base motor carb gaskets sequence...

That "hot-slot" design also culminated in the second-largest Chevrolet safety recall since the V-8 motormount failure issue; iron-intake hot-slot cars with Quadrajet carburetors had the bowl plugs fall out, resulting in engine fires. I was in the middle of that one, and remember it well.

John------



There was one application that used an aluminum manifold with heat slot and Q-Jet carb. That application was 1968-69 Corvette L-36. I think those were the only aluminum manifolds that were ever equipped with a heat slot. That was a real dumb idea, especially for an aluminum manifold.