I've got a 68 396/325hp with the stock quadrajet four barrel that has issues starting when hot.
Car starts great when cold, runs great, idles great. When I restart it after 45 minutes it wont start and belches gas out the top. I go to start it cold and it fires up.
Weather condtions were hot both times and I had changed the accelerator pump a few weeks ago. Any ideas?
Thanks, Tom

Sounds like another hot fuel issue. Read my thread "Another Quadrajet Boiling Gas Thread" for some ideas on what to do.

I've got a 68 396/325hp with the stock quadrajet four barrel that has issues starting when hot.
Car starts great when cold, runs great, idles great. When I restart it after 45 minutes it wont start and belches gas out the top. I go to start it cold and it fires up.
Weather condtions were hot both times and I had changed the accelerator pump a few weeks ago. Any ideas?
Thanks, Tom

I've heard and had boiling gas in my Qjet, mainly due to today's sorry gas, but never had a condition where gas spewed out and up. I could hear it "boil", but no dripping or flooding. Does it flood in the throttle bores, or does it actually come out of the vent tubes? The accelerator pump has nothing to with gas physically coming out of the carb- that is due to uncontrolled fuel flow into the carb due to something else.

The first thing I would try in your case would be to to make sure the gasket "stack" is correct and has the right gaskets if your intake is stock and has the trough, try a phenolic spacer if necessary...The CORRECT gasket stack really should fix this problem, though.

I would see a bunch of white smoke coming out of the air filter and even some gas shooting out the top.
Also, can someone explain the correct operation of the accelerator pump? When it squirts the streams in to the carb is it supposed to shoot in to the primarys?

Thanks for the suggestions. I'll dig in to this and see what I find.
Have a good Memorial Day!

I would see a bunch of white smoke coming out of the air filter and even some gas shooting out the top.
Also, can someone explain the correct operation of the accelerator pump? When it squirts the streams in to the carb is it supposed to shoot in to the primarys?

Thanks for the suggestions. I'll dig in to this and see what I find.
Have a good Memorial Day!

When you hit the gas pedal, gas shoots into the primary bores from the accelerator pump. That is why when starting a carbed car, you should hit the gas once or twice to prime the engine for starting.f A Qjet float bowl isn't huge, so a substantial amount of gas shooting out would lead me to believe that you might be getting too much fuel pressure, and that in turn is overwhelming the needle and seat. You really need to make sure that if your intake is stock, and has the trough, you have the correct stack of gaskets in the correct order.

One thing I've wanted to find since gas started getting crappy was an additive that actually raises the boiling point of gas. I'm not sure if 104+ or any of that stuff will work for this, but I might try it next time. That is one thing we can't control- gas quality has really gone downhill since carbs on production cars went the way of the Dodo.

I do have the stock manifold and carb. What is the correct order to stack the gaskets? It currently has the gasket on the manifold first and then a thin metal gasket, then the carb. I may have reversed them when I changed out the accelerator pump. Should I be using a heat shield?

Tom

I do have the stock manifold and carb. What is the correct order to stack the gaskets? It currently has the gasket on the manifold first and then a thin metal gasket, then the carb. I may have reversed them when I changed out the accelerator pump. Should I be using a heat shield?

Tom

I believe you are one gasket short..I have a 1969 cast iron small block manifold with the trough. I have three gaskets under my carb. From the manifold up- asbestos or equivalent heat resistant gasket WITH the trough, thin metal gasket NO trough, and then a Mr. Gasket thickER carb gasket on top of the thin metal gasket and below the carb- NO trough..I have the original asbetos gasket I use, but you will probably have to find an equivalent to try out.

If it were me, I would get the correct gaskets and try them first. The reason why is that you probably have a functioning choke, and if you put on a phenolic spacer, you will have to remove the choke or fabricate a new choke rod. My carb does get hot, but I don't really have boiling gas. I can sometimes hear it percolating, but that is just the gas we have now, and it doesn't really cause me any issues like you are describing. The other problem with a spacer is hood clearance depending on how big you go.

I did install another spacer gasket and still have the same problem. I'm wondering if the float bowls are set too high and its dripping gas in to the engine when hot. It was probably OK before because my accelerator pump wasnt functioning before and it would start. Now that I have the pump working properly I'm quite possibly loading the engine up with even more gas when I hit the gas pedal.
Does that sound possible?
Thanks, Tom

I did install another spacer gasket and still have the same problem. I'm wondering if the float bowls are set too high and its dripping gas in to the engine when hot. It was probably OK before because my accelerator pump wasnt functioning before and it would start. Now that I have the pump working properly I'm quite possibly loading the engine up with even more gas when I hit the gas pedal.
Does that sound possible?
Thanks, Tom

Yes..

First, a Qjet has a single float bowl, and only one float. So if your float is set too high, it can absolutely cause flooding. If the boosters are dripping during or after you drive it, you might have a high float level. As you know if you took the carb apart, the float is an internally adjusted float. You CAN adjust it on the car, but I learned a trick from a Qjet guy here on TC that it's easier to set it by turning the carb upside down, bend the tang, etc. until you get the right level from the top where it is measured from. It IS easier and more exact, IMHO. Yea, you have to take the carb off the car, but if it's right it's right, and you don't have to keep readjusting to get it right.

A car will actually run with no accelerator pump, but it will be sluggish right off idle and can be a pain to start when cold. All it really is is a fill in circuit when going from one carb circuit to the other.

The gasket stack is more than likely OK if you have them in the correct order and added another gasket..Next step might be to do as you said and make sure the float level is ok, or even that the float is newER and not sinking if it's an old one. A sunk float can also cause excess fuel. One caveat- DO NOT overtighten any bolt or screw on the top of a Qjet.

You could also have leaking well plugs in your carb..If you're going to take it off the car, you might as well TEST THIS before putting it back on. A simple test can be to put some gas in the bowl, top on or off, suspend the carb over some paper or cardboard, leave it overnight, see if it drips. This doesn't have anything to do with boiling gas, BUT it is a worthwhile test to see of you might have an internal leak compounding the problem.

I will give that a try, Thanks!