C2 '66 3606 AIR Carb

[Mark P.]

This may be a dumb question that will prove my ignorance, but I have to ask it....what is the purpose of the stainless baffle plate between the carburetor and the gasket on my 390 hp car? It seems to me that the passages in the carb base and below in the manifold are blocked by this plate, but I don't know what the purpose is. Could anyone take a moment to explain, and respond as to whether or not it would run without it?

Thanks so much for the info.
Mark

[Jack H.]

Re: C2 '66 3606 AIR Carb

Baffle plate is cut open in the center beneath the four individual carb barrels. It does two things:

(1) Serves to distribute the heat generated by the 'hot slot' in the intake manifold (indented slot at rear) evenly.

(2) Acts as a partial heat reflector to thwart percolation of the fuel bowls during periods of low RPM operation (idle).

[Gerard F.]

Re: C2 '66 3606 AIR Carb

Mark,

The heat slot in the intake manifold brings exhaust gases to the bottom of the carburetor against the baffle, and is intended for fast warm-ups in cold weather. In the long run, it tends to cook your carburetor.

Unless you live in the tundra, it is advisable to block the two holes at the ends of the heat slot with freeze plugs. But you still need the baffle on top of the base gasket for heat reflection and distribution.

Jerry Fuccillo
#42179

[Mark P.]

Re: C2 '66 3606 AIR Carb

Are you saying to nlock the two holes in the carburetor, or in the manifold?

[Joe L.]

Re: C2 '66 3606 AIR Carb

Mark------

If the "heat slot" in the carburetor flange of your manifold is "active" (i.e. the holes in each end not previously plugged), then the proper installation (between carburetor base and gasket) of the stainless heat shield is absolutely critical. Without it properly installed, the carburetor will be ruined very rapidly. Even with it in place, the carburetor will be damaged but it will take a lot longer. I always recommend that the heat slot end holes be plugged and the heat slot "de-activated". I still recommend the installation of the baffle, though, even if the heat slot is so "de-activated".

Chevrolet abandoned the "heat slot" for all engines after the 1969 model year.

[Mark P.]

Re: C2 '66 3606 AIR Carb

Any specific recommendation on the best way to plug or deactivate it? It definitely has not been plugged in hte past and I just put the correct carb back on the car and would not want to do any damage before I get it going again.

Thanks,
Mark

[Joe L.]

Re: C2 '66 3606 AIR Carb

Mark-----

With the manifold on the car, the best way is to use soft plugs (like "miniature" freeze plugs) to plug the holes. Just drive them in with a punch of the same approximate diameter as the ID of the plug. As I recall, a 3/8" plug fits, but I'm not 100% sure about the size.

[Mark P.]

Re: C2 '66 3606 AIR Carb

Thanks, Joe and all who responded. I'll get to work and plug them up. Chances are pretty good that I won't need to keep it warm in the cold Utah winters. It won't be driven much then anyway.

Thanks again,
Mark

[Gerard F.]

Here's what I used

on a 67 327/300 CI intake manifold for a 3810 holley:


I think they were 5/16" if my memory serves me right. Yours could be different.
Check the size with a bolt in the hole in the manifold first for a tight fit. Then get the right size freeze plug and use the bolt to put it in place.

Some have also threaded a plug in the manifold heat slot holes.

Jerry Fuccillo
#42179

[Gerard F.]

Sorry, 7/16" freeze plugs

Mark,

is what I used not 5/16". See this thread from the archives:

https://www.ncrs.org/forum/archive23.cgi?review=196798

Jerry Fuccillo

[John H.]

Re: Sorry, 7/16" freeze plugs

It should look like the photo below when you're done. That "hot-slot" was the cause of the biggest safety recall in Chevrolet history in 1969 for engine fires in Q-Jet-equipped cars when the float bowl plugs fell out from the heat.