C1 - 1962 - AFB Carburetor Question

[Michael B.]

Good Morning,

I am a recent buyer of a nice driver level C1 Corvette. 1962.

I have been driving and enjoying this great car since I bought it in late April of this year. I have

When I bought it, the 327/300 hp engine had been replaced with a 350/300 hp from 1970. I believe that it was rebuilt at some point, because it feels very strong for an engine of that age, and that drives out well, with no issues.

I say no issues... The engine had a Carter WCFB carburetor that apparently was famous for stalling out during long left turns. After asking questions, I was advised that I should pick up a Carter AFB 3721-SB. I did, and had it installed.

Being new to this hobby, and to the Witchcraft of Carbureted Engines, I had a mechanic install the new carburetor. He told me that since the intake manifold of the 350 engine wasn't a direct fit, he used an adapter plate to make sure that it would work as it should.

It ran great after I picked it up until about 2 weeks ago. When I get into the car, on a cold start, it usually fires right up when I turn the key. But If I have driven it for a while, and have the engine up to temp, and then turn it off to go into a store; it takes it a long time to start when I turn the key. By "a long time", I mean 5 to 10 seconds of the engine turning over. It eventually starts up, but when it does, it runs rough for a bit, and then smooths back out.

I am a member of the Corvette Forum. I asked this question and was pretty much made to feel like an idiot because I apparently do not know how to ask the question correctly, and/or do not have 100% understanding of their questions to give them the exact answer that they were looking for. So I decided that I didn't feel like playing that game, and would stumble through it myself until I am able to figure it out. (I could always take the car back to the mechanic, but I want to learn).

One of the comments made, were that if I am using an AFB carburetor, I should also have a Baffle Plate (Stainless Steel), and Insulator spacer, and the Gasket(s). I was told that the insulator spacer if needed in order to guard against "Heat Sink", fuel "boil/peculation". I can see that.

I know that I have a (Stainless Steel Plate, and Gaskets, but I am not aware of an insulator spacer.

Can you please comment to let me know your thoughts, and correct part numbers that I should look for?

Thank you,

Michael
Charlotte, NC

[Wes S.]

Re: C1 - 1962 - AFB Carburetor Question

Zip Products Catalog page 25 item CZ-943

[Mike E.]

Re: C1 - 1962 - AFB Carburetor Question

Michael,
The phenolic spacer is not a bad idea. Before you jump into that, I would check the amount of clearance between your air cleaner and the hood, because I don't know how thick your adapter is. (The one that your mechanic added.) Generally, the clearance is pretty tight. Easiest way to do that is some clay/putty/silly putty material.

[Michael B.]

Re: C1 - 1962 - AFB Carburetor Question

Michael,
The phenolic spacer is not a bad idea. Before you jump into that, I would check the amount of clearance between your air cleaner and the hood, because I don't know how thick your adapter is. (The one that your mechanic added.) Generally, the clearance is pretty tight. Easiest way to do that is some clay/putty/silly putty material.

Hi Wes, Thank you for the quick response. The adaptor plate that is currently there, looks to be about 3/8 to 1/2". I was concerned with the hood space as well. I have putty that can be used, so I'll see how much room is there.

Thanks again.

Mike

[Timothy B.]

Re: C1 - 1962 - AFB Carburetor Question

Mike,

I'm over at the corvette forum also and am sorry if people were rude to you, some definitely have a little edge to them .

From your description it sounds like a heat related issue so I would start with the simple stuff like check the fuel lines to make sure they are not touching any heater hoses etc.

Also, if your engine has a heat riser, wire it open full as that will take exhaust heat from the cast iron intake manifold. Check to see if the engine is set up for ported or full manifold vacuum advance, you want full manifold vacuum advance so idle timing is approx 8* initial plus 12-15* vacuum advance for a total idle timing approx 21-23*.

The heat shield used on the period correct factory manifold served the purpose of keeping the hot exhaust crossover gas off the carburetor bottom but your 1970 intake manifold probably does not have that. It's still a good idea if room allows to isolate heat from the carburetor base with a thin spacer.

[Duke W.]

Re: C1 - 1962 - AFB Carburetor Question

The hard hot starting issue is probably caused by percolation, which is a common issue. The hardware discussed above doesn't apply to your installed manifold because it originally had a Quadrajet. That's why it needed the adapter.

Is the AFB vintage or a modern Edelbrock clone?

Since you have a non-standard configuration, look for an adapter made out of non-metallic material that will act as a heat insulator. Wrapping the fuel lines in insulating tap or sleeves has been used to good effect by some, reducing carb temperatures by up to about 30 degrees.

As previously mentioned, wire the heat riser valve open, and it would be a good idea to check the spark advance map, beginning with the number on the VAC mounting bracket and report vacuum at specified idle speed to determine if the VAC passes the Two-Inch Rule.

Duke

[Frank D.]

Re: C1 - 1962 - AFB Carburetor Question

I also apologize for the way you were treated on the Corvette Forum - things go sideways over there at times...

The WCFB stall-on-left-turn fix is a known issue with those carbs and can be corrected in about 1/2 hour....if you are having hot soak/percolation problems I don't know if you're accomplishing anything from switching from the cast iron and pot metal WCFB to the aluminum-bodied AFB...

I ran a '61 dual quad WCFB stock setup for 12 years and solved the heat soak problem in Orlando summer heat... The combination of fuel injection intake manifold gaskets to block off the heat riser passages, wiring open the passenger side heat riser valve and 1/4" phenolic spacers did the trick.... The car came from the factory withOUT vacuum advance but I added it..