1963 cold and hot start problems

[Nick K.]

Re: 1963 cold an hot start problems

Thanks for all the input. The choke pull off piston seems to be the culprit of the choke sticking open. After I disassemble the choke and clean and lubricate the pull off piston and bore with graphite it will work great for awhile. Then just goes back to sticking again within a short period of time. I've thought of converting to an electric choke but every time I think of modifying the car I think or other issues that could be caused by that modification.

[Harry S.]

Re: 1963 cold an hot start problems

Thanks for all the input. The choke pull off piston seems to be the culprit of the choke sticking open. After I disassemble the choke and clean and lubricate the pull off piston and bore with graphite it will work great for awhile. Then just goes back to sticking again within a short period of time. I've thought of converting to an electric choke but every time I think of modifying the car I think or other issues that could be caused by that modification.

Nick, sometimes it needs more than cleaning. I have some 8000 grit black sandpaper that I used with water after cleaning. I did the piston and the tube. I did not use any graphite or lubricant. My 63 WCFB has been fine for the last 18 months.

Another problem is that the housing can warp because of the heat thus putting the tube out of alignment with the piston. Replace the housing with NOS if you can.

[Duke W.]

Re: 1963 cold an hot start problems

Thanks for all the input. The choke pull off piston seems to be the culprit of the choke sticking open. After I disassemble the choke and clean and lubricate the pull off piston and bore with graphite it will work great for awhile. Then just goes back to sticking again within a short period of time. I've thought of converting to an electric choke but every time I think of modifying the car I think or other issues that could be caused by that modification.

There is a tiny o-ring that seals the vacuum passage between the choke housing and the AFB main body. They should be included in the carb overhaul kits, but maybe not. If this o-rng is not in place and seated properly, there will be a vacuum leak and dirt will get into the choke vacuum break bore and cause the piston to be sticky, which will prevent the choke valve from fully closing when you floor the throttle to set the choke for a cold start.

Duke

[Nick K.]

Re: 1963 cold an hot start problems

Thanks Harry and Duke for the input. I'll take another run at it. Any idea if the choke housing and piston is available anywhere? Might just replace those parts as they could be worn or warped.

[Harry S.]

Re: 1963 cold an hot start problems

LIC and others usually sell refurbished originals for about $75.00, I got one and wasn't real pleased. Look for NOS on Ebay, Corvette Forum, etc.

Duke, yes. That O-ring is essential.

[Stuart F.]

Re: 1963 cold an hot start problems

I always had the sticking problem as a sort of white corrosion builds up and will continue to do so as long as you have the stock fresh air (hot) tube connected. It's just the nature of the beast. Remember; just because you change to an electric choke doesn't mean you have done something that can't be easily reversed for judging. I use a special electric choke mechanism that I bought frome J.C. wHitney many years ago. It uses a thermal sensor mounted on the manifold with a single bolt in the existing tapped hole on a stock 340hp aluminum manifold back of the carb. The bi-metallic spring in the choke housing has a round tab on the end that captures the piston pull-off tang such that it assists operation by pulling the linkage and pushing it (closing and opening). The piston still works in response to engine vacuum just as before. I have had no problem as you describe for a number of years now. My intent was to limit heat transfer to the carb as well. I raised the carb up on the manifold using the phenolic spacer from the L-75 300 hp, but on a L-76 340 hp you need to just use the spacer with two (2) correct 340 hp gaskets from Dr. Rebuild in a sandwich. Only! Dr. Rebuild has the correct base gaskets. All others will likely leak vacuum. With the carb raised, you then use a fuel hose connection between the filter and the carb. This makes up the 3/8"+ difference plus eliminates the steel tube heat transfer from the fuel line. Using the electric choke without the fresh air tube eliminates that source of heat transfer. I see significant temperature drop wherever I measure it on the carb with my I.R. gun. In addition, I use Tomco inlet valves instead of needle/seats. They allow me to lower my floats without any performance concerns as they will flow a lot more fuel. Note that all of these changes are easily reversed and, oh yes, the air filter housing still clears the hood with the 3/8" + elevation of the carb.

The hot starting procedure previously described is spot on. It works very well for me. On cold starts, my choke sets fully with a spec high idle of around 1500 rpm on the high step and kicks down very normal. The thermal sensor then controls the warm up choke setting rpm based on engine temperature even during cold ambient outdoor conditions. It never kicks off too soon to cause bogging or hesitation, but is off usually after a few blocks driving. An Edelbrock electric choke works ok, but I much prefer mine. I only have one more of these on my shelf.

About your problem, make sure your B28 VAC meets spec. Check it with a Mity Vac. I bought a number of cans from venders in the past that were labeled B28's, but never performed to spec. Also, make sure it will hold vacuum. I also have used Pertronics over the years, but if you still have an early pre- II model, I would change it if I were you as I did to a - II unit, use their Flamethrower coil, and run a jumper around your ballast resistor to give you a full time 12 volt input. It's a simple swap.

Stu Fox

[Nick K.]

Re: 1963 cold an hot start problems

Thanks Stu for the info...So you are saying that the 300 HP AFB originally used a phenolic spacer with 2 standard base gaskets in a sandwich? Interesting...Any recommendations for a supplier of these spacers? I'm using a vac can that kicks in at about 6 to 7 +/_ " vac if I remember correctly. Using a pertronix but not sure what generation it is. Have already soldered a by pass in the ballast resisitor. The elec choke mod is something I will pursue. I seem to recall an article in Hot Rod mag or the Restorer about this modification using an Edelbrock Performer electric choke kit.

[Stuart F.]

Re: 1963 cold an hot start problems

Nick;

just to clarify; the 300hp uses the phenolic spacer, but requires the use of a stainless steel plate in conjunction with the spacer to block off the heat passages under the carb base. My use of the spacer on my 340 hp is different in that I use the two 340 hp base gaskets with the spacer in a sandwich. If you have jumpered your ballast resister to get the full 12 volts input, this should only be done if you have the Pertronics II unit and their Flamethrower coil (not a Pertronics I or a stock coil). The II unit requires a full 12 volt input. Both the spacer and the 340 hp gaskets can be had from Dr. Rebuild. They are the only supplier of the correct 340 hp base gaskets that I know of. Take a look at their catalog and you will see what I mean.

Stu Fox

[Nick K.]

Re: 1963 cold an hot start problems

So you use a base gasket then phenolic spacer and then another base gasket. Do you also use the steel plate to block off the heat passages?

[Tim G.]

Re: 1963 cold an hot start problems

We had this come up with a '65 at our Saturday shop. It was the ignition switch. We took it apart, cleaned the contacts and the fellow got the car home. He ordered another switch, but that was the problem. Contact was made in the start position, but when the key was released it died. Sometimes it would run for a moment and stop.