Carb gasket and heat shield questions

[Chuck Z.]

Background. Original owner of my 1970 Corvette with the LS5 engine and 4 speed transmission ordered & purchased from M F Jones Chevrolet in Dallas, Georgia and took delivery on March 16, 1970. Back in 1975 when the Q-jet was acting up, I took it to a Corvette Shop in San Diego to help me out. After discussions on the worthiness of the Quadrajet, the decision was made to replace it with a Holley spread-bore. Car ran great for years. Please don't ask what this 27 year old naval aviator did with the original carb. I paid dearly for that mistake much, much later in life.

Fast forward to 2015 when I make the decision to do the right thing for my car and go on the hunt for the correct 7040205 Q-jet. As I previously mentioned, it wasn't cheap nor was the rebuild and restoration. Its only money.

So now to my questions. Did the car come with a heat shield below the carb? Recently I was at the Muscle Car Museum in Punta Gorda, FL and all of the 70 Chevelles with 454 engines and 4 speed transmissions all had heat shields. So I am assuming that mine should have one. Correct? Next question has to do with the gaskets. Are there two gaskets? One below the heat shield and the intake manifold and another one above the heat shield and below the carb?

Last question, any recommendations where to buy these parts? Dr. Rebuild comes to mind. Any chance to find the original heat shield? Looking closely at the 70 Chevelle at Muscle Car Museum, I noticed that the heat shield had a part number on the very front. Would love to find an NOS heat shield but realize I may just have to settle for an aftermarket.

Look forward to hearing from you Corvette guru's.

Thanks,
Chuck

[Mike E.]

Re: Carb gasket and heat shield questions

Chuck, you can save a few bucks here. You don't need the heat shield: per the new 70-72 JG, p. 107. "Only 1970 vehicles equipped with California emissions had a brushed aluminum shield........". The carb would be a different number. (7040505)

[Mark E.]

Re: Carb gasket and heat shield questions

I either started or contributed to a thread awhile ago on this subject, so you'll find more information by searching this topic.

As I recall, heat shields were used on many NA9 (CA emission) Chevrolets. 1970-71, maybe other years too. But it's unclear if they were used on LS-5 Corvettes. If they were used, they were most likely on NA9 Corvettes, which featured 7040505 Q-Jets (vs. 7040205 for 49 state cars) and evaporative emission canisters. The shield helped dissipate heat to reduce percolation in the fuel bowl. This shield may have been added because NA9 cars were more susceptible to percolation from higher temperatures due to retarded timing and leaner fuel mixtures.

One PN I know of is 3969837. They're not hard to find on eBay. Two gaskets are used with the shield, one thicker than the other.

[Joe L.]

Re: Carb gasket and heat shield questions

Background. Original owner of my 1970 Corvette with the LS5 engine and 4 speed transmission ordered & purchased from M F Jones Chevrolet in Dallas, Georgia and took delivery on March 16, 1970. Back in 1975 when the Q-jet was acting up, I took it to a Corvette Shop in San Diego to help me out. After discussions on the worthiness of the Quadrajet, the decision was made to replace it with a Holley spread-bore. Car ran great for years. Please don't ask what this 27 year old naval aviator did with the original carb. I paid dearly for that mistake much, much later in life.

Fast forward to 2015 when I make the decision to do the right thing for my car and go on the hunt for the correct 7040205 Q-jet. As I previously mentioned, it wasn't cheap nor was the rebuild and restoration. Its only money.

So now to my questions. Did the car come with a heat shield below the carb? Recently I was at the Muscle Car Museum in Punta Gorda, FL and all of the 70 Chevelles with 454 engines and 4 speed transmissions all had heat shields. So I am assuming that mine should have one. Correct? Next question has to do with the gaskets. Are there two gaskets? One below the heat shield and the intake manifold and another one above the heat shield and below the carb?

Last question, any recommendations where to buy these parts? Dr. Rebuild comes to mind. Any chance to find the original heat shield? Looking closely at the 70 Chevelle at Muscle Car Museum, I noticed that the heat shield had a part number on the very front. Would love to find an NOS heat shield but realize I may just have to settle for an aftermarket.

Look forward to hearing from you Corvette guru's.

Thanks,
Chuck

Chuck-------


As Mike has mentioned, your application did not originally use a heat shield. Only cars originally delivered to California and equipped with EEC had the shield. I don't know why the 1970 Chevelles you saw had the shield unless they were California cars because the situation for Chevelles was the same as for Corvettes. Now, if they were actually 1971 Chevelles, that's different.

The gasket originally used for your application was GM #3967470. Dr. Rebuild has an excellent reproduction of this gasket. By the way, this gasket is not configured as it appears in the AIM drawing.

You're lucky yours was not originally a California car. If you think finding a GM #7040205 carburetor was difficult and expensive, you should try finding a GM #7040505!

[Mark E.]

Re: Carb gasket and heat shield questions

Chuck,

What air cleaner did you use with your Holley Spreadbore? I know the '70 open element doesn't fit over the Holley, and the PCV inlet of '70 twin snorkel interferes with the secondary linkage.

I think the base of a 73-74 will fit since the PCV inlet connects on the side instead of the bottom. And I think the '70 twin snorkel lid will fit the 73-74 base.

I have a couple of these carbs, and want to fit them to the car at some point.

[Chuck Z.]

Re: Carb gasket and heat shield questions

Hi Mark,
Art Gallo was the owner of the shop in San Diego that worked exclusively on Corvettes back in the early '70's. When he installed the Spreadbore on my car he also installed an open element air cleaner that fit the Holley. When I made the decision to go back original on my car I advertised the Holley on Craig's List along with the air cleaner. I do remember that the air cleaner used a much smaller filter. Smaller in the fact that it was not as high as the original air filter.

Thanks,
Chuck

[Chuck Z.]

Re: Carb gasket and heat shield questions

Thanks Joe.

[Mark E.]

Re: Carb gasket and heat shield questions

Hi Mark,
Art Gallo was the owner of the shop in San Diego that worked exclusively on Corvettes back in the early '70's. When he installed the Spreadbore on my car he also installed an open element air cleaner that fit the Holley. When I made the decision to go back original on my car I advertised the Holley on Craig's List along with the air cleaner. I do remember that the air cleaner used a much smaller filter. Smaller in the fact that it was not as high as the original air filter.

Thanks,
Chuck

Thanks Chuck. A bolt on replacement for a Q-Jet was probably a good product idea for Holley at the time. Too bad they didn't think through the air cleaner fitment.