'64 HARD STARTING WHEN EGINE HOT

[Mike Cobine]

Re: '64 HARD STARTING WHEN EGINE HOT

Since the '63-'65 300 hp auto and the '66-'67 300 hp all used 2 inch exhaust and the cam for the 250 hp and 300 hp was the same, those are not the reason your car was flooding.

A carb is an on-demand item. It cannot force more air or gas in unless it is broken. Then it will force more gas in due to leaking or will allow more air due to leaks. So you can put a huge carb on or a small one, and they wil both run with some conditions. One too big will end up bogging due to the engine being unable to pull enough air to keep the airflow speed high enough or may flood because the accelerator pump is too great, forcing raw gas in. But sitting idling hot will not flood just because it is bigger. And a 600 cfm is not really big.

[Harry Sadlock]

Re: '64 HARD STARTING WHEN ENGINE HOT

Mike, it was running crummy, backfiring, and lots of black smoke. Actually, I believe I was looking for any excuse to get the non-stock gear off the car. An emotional decision. After looking at the posts, I probably had a serious carb. problem.

Thank You

Harry

38513

[randy greenbaum]

Re: Basics, people

Mike,
The float is brass and new so I assumed it is OK. Probably not the wisest thing to do considering how things are made today. No black smoke while ideling. Black smoke while starting after sitting 30 min's or so. Could it be not enough air flow? Maybe a high flow filter?

[Mike Cobine]

Re: '64 HARD STARTING WHEN ENGINE HOT

Excuses to remove the non-stock stuff are usually easy for us, but totally bewildering to anyone outside this hobby.

The understandable flaw in the GM QuadraJet was based on price, much cheaper to produce a composite float when you consider that it went on millions of cars, and literally saved millions of dollars.

For a company like Edelbrock to continue such on a low-volume, high-priced item is inexcusable.

[Timothy B.]

Re: Basics, people

Randy,

I think that your problem may be fuel boiling out of the carburetor because of heat soak after the engine is hot and shut down. On original cast manifolds there is a gasket, insulator and shield between the carburetor and manifold because of the heat groove. If it's a aluminum intake and the carburetor is getting hot after shut down you may want to restrict the heat crossover and make sure the heat riser valve is opening and not rusted.

[Mike Cobine]

Re: Basics, people

New info, new solution. It sounds like the well plugs on the lower section of the carb body are leaking. This is very common and usually fixed with only minor problems.

You can search Yahoo for Quadrajet well plugs and see the many sites about this. One is listed below.




4MV Quadrajet Assembly

[Joe C.]

Re: Basics, people

It might be fuel percolation during heat soak. Lower the float level in small increments until the problem disappears. With a 250 HP engine, and probably a 3.08 axle, your max flow capacity will be about 480 cfm.@ WOT, @redline, so lowering the float level will not cause you to run away from the gas in the bowl.

[Mark H.]

Re: '64 HARD STARTING WHEN EGINE HOT

I'd suggest you replace the aftermarket stuff with the real McCoy. My '64 is a 300hp car. It ran poorly and had similar hot starting issues when I got it - with an incorrect electric choke Carter carb installed on the original intake. I swapped the Carter (cruddy beyond belief) out for a new 600cfm Edelbrock - looking for a quick fix. The engine ran much better, still had the hard starting problem, and stumbled when hot as well. I rebuilt the engine, which solved some other issues, but the hard starting and stumbling when hot remained. I finally bit the bullet, got a proper Carter AFB off ebay, sent it off for a rebuild, installed it with all the proper spacers and like magic, the problem went away. You just can't beat that old technology - it all works together.

[Les Jacobs]

Re: '64 HARD STARTING WHEN EGINE HOT

Another possibilty.. float valve seat. If it is not snug, gas can bypass the float needle/seat via the seat threads and overflow the carb resevoir flooding the carb. After shutdown the residual fuel pump pressure can force enough gas into the carb to flood it. I have personal experience with this, and watched a newly rebuilt carb spew gas out of the air horn gasket after shutdown. (It also ran extremely rough at hot idle).

[Harold #43147]

Carb

After you shut the car off remove the air cleaner and watch to see if vapors start coming out of the air horn if there is, fuel is leaking into the intake make sure your choke stays open also after sitting for that time period your talking about is this performer carb a remake of the old carters? Check your fuel pump pressure if you see vapors all the problems the guys above said could be the problem Float level may seem alright when cold but changes with heat soak. I bought a new Edelbrock 850 cfm remake of the Qjet and the main metering wells were leaking out of box the same problem you have car would sit for 20 min. and would be flooded

[Mike M.]

Re: Carb

Being a 600 cfm carb, I bet it is the Edelbrock version of the Carter AFB. The floats probably need readusting because of the wedge shaped spacer under the carb, which probably tilts the carb forward. My recommendation is to lower both floats by 1/16" and see if that helps. AFB's are also sensitive to heat which causes boilover, but if the carb spacer is phenolic, this should better isolate the carb.
Mike

[John H.]

Re: '64 HARD STARTING WHEN ENGINE HOT

Mike -

From off-line conversation, this is the Edelbrock AFB clone, not the Q-Jet clone; I'd have just rebuilt the WCFB and moved on, as we all know about the marvelous technology advances from the WCFB to the AFB