'62 340 hp. question

[Rex M.]

Can someone tell me if the 1962 340 hp. used the insulator spacer between the carburetor and the intake manifold? Thanks.

[Joe L.]

Re: '62 340 hp. question

Can someone tell me if the 1962 340 hp. used the insulator spacer between the carburetor and the intake manifold? Thanks.

Rex-----


I show that the insulator was used only for 300 hp applications. It was GM #3828231 and was used in conjunction with a baffle plate of GM #3799354.

By the way, the reason that the 300 hp used the insulator and baffle was because the 300 hp used a cast iron manifold with carb "heat slot" system. When this system is used, it is necessary to use an insulating gasket and baffle plate to protect the carburetor from direct heat of exhaust gasses passing through the slot. The 340 hp used an aluminum manifold with no "heat slot", so no insulating gasket was necessary, even though the carburetors for the manual trans 300 hp and 340 hp were the same.

[Stuart F.]

Re: '62 340 hp. question

Does that then mean the same cast iron manifold is used for the 250hp that uses the WCFB with a heat slot?

I use the spacer on my 63 340hp anyway along with two base gaskets (sandwiched) as a means to combat the heat soak problem with todays gas. Using an IFR gun, I see 35 to 40 degrees reduction in temperature at the carb at full warm. It may not be correct, but it is necessary if you chose to drive your car these days. On the down side, one must alter the incoming fuel line from the filter. I use a hose.

Stu Fox

[Joe L.]

Re: '62 340 hp. question

Does that then mean the same cast iron manifold is used for the 250hp that uses the WCFB with a heat slot?

I use the spacer on my 63 340hp anyway along with two base gaskets (sandwiched) as a means to combat the heat soak problem with todays gas. Using an IFR gun, I see 35 to 40 degrees reduction in temperature at the carb at full warm. It may not be correct, but it is necessary if you chose to drive your car these days. On the down side, one must alter the incoming fuel line from the filter. I use a hose.

Stu Fox

Stu-----


The 1962 250 hp used a different manifold than the 300 hp. I don't think the 250 hp manifold had a heat slot.

[Rex M.]

Re: '62 340 hp. question

Thanks for the help Joe. That is kind of what I was thinking. I just couldn't find anything that directly addressed the 340hp. application. I did look very closely at the photos in Noland's book and they clearly show the 340hp. without the insulator between the manifold and carburetor.


I show that the insulator was used only for 300 hp applications. It was GM #3828231 and was used in conjunction with a baffle plate of GM #3799354.

By the way, the reason that the 300 hp used the insulator and baffle was because the 300 hp used a cast iron manifold with carb "heat slot" system. When this system is used, it is necessary to use an insulating gasket and baffle plate to protect the carburetor from direct heat of exhaust gasses passing through the slot. The 340 hp used an aluminum manifold with no "heat slot", so no insulating gasket was necessary, even though the carburetors for the manual trans 300 hp and 340 hp were the same.[/quote]

[Timothy B.]

Re: '62 340 hp. question

Rex,

One thing you may want to check is the thickness of the 340hp gasket under the carburetor. Somewhere I read this gasket is thicker than the papergaskets but I can't say for sure because I may be thinking about another year carburetor.

The aluminum dissipates heat so no problem heating the carburetor base when it's sitting on the aluminum manifold. The stainless baffle on 300hp engines is supposed to conduct the heat from the insulator to the carburetor base but with todays gasoline it's best to plug the hot slot under the carburetor and keep the gasoline as cool as possible. Some people put gaskets between the carburetor and baffle and this will also block the heat transfer to the carb base.

There is also heat from the choke hot air tube to the carburetor base and mine gets plenty hot, both engines share this circuit.