Ok so my 86 firebird runs fine and dandy but if it idles sitting still, or runs at about 2500 rpms or higher at a low speed, and you try to lay into it it does fine for 1-2 seconds then starts cutting out until you let out of the throttle. I'm thinking that my fuel is vaporizing or Im just pulling in to much hot air. So I'm gonna do some permanent alterations by cutting up my hood and making the front vents fully functionable unless somebody gives me some different advice.

The car is a 86 with a rebuilt 350, thumpr cam, eldebrock carb and intake, and hooker headers oh and its a crappy t5, posi 3.42 rear

thanks

 

I really feel I must ask -- did you eat paint chips as a child?

You're got a 350, basic-- nothing too fancy, with a medium cam? pretty basic parts on it, and you think for some reason, you, and only you, require a cut up hood to vent air into the engine bay?? Your problem wouldn't be solved by cutting up your hood - although I would love to see the result, and your follow up post...


- Ok, if you think your fuel is vaporizing - two questions - what style fuel pump do you have? A return style mechanical pump? Stock in tank electric and a regulator? Is the regulator a bypass style? Is your fuel line running close to your headers? Are your headers coated?

- If you roll into the throttle slower, does it work ok? Can you drive it at say 3000 RPM, under load, in a higher gear, or will it stumble?

- How's your carb settings? You go over it with a fine tooth comb?

- Fuel filter - what style is used?

 

Also need to know what initial and total timing is - I had same issue and I'm blaming it on timing, I changed mine a week ago and haven't had any further issues so far.

 

in reply I may or may not have ate paint chips as a child...
but I thought about just enlarging the hole under my heat extracters but it started raining yesterday. But I have a mechanical fuel pump with the return. and my headers aint coated my fuel line runs like it did with on the 305. it only happens when its hot thanks again.
fuel filter is a clear plastic one, carbs pretty well good,

 

Are you running a thick insulating carb gasket or a thin one?

 

When you say "cutting out" is it pinging and wanting to die insted of pulling?

If it's pinging at higher RPM's WOT first check timing. Then you may need a fuel pressure gauge. Mechanical fuel pumps springs wear out and they can feed a carbs bowl at low RPM but not WOT high RPM, the bowl runs dry and the pinging and surging starts. When you let off the throttle the weak pump fills the bowl again.

Fuel pumps are dirt cheap if it's an older one you may just want to change it and see. That is if the timing checks out.

 

pretty thin carb gasket. Its not pinging more like its just running outta fuel. Retarded the timing a bit will see what happens. It never has the problem unless I'm moving slow before hand or setting still with it idleing and it dont do it unless its under a load, and never early in the morning

 

No I dont think only I need to cut up my hood, Maybe that would fix lots of peoples problems

 

Since you believe this is a heat related fuel problem the thick carb gaskets like the ones the OEM Qjet use help lessen heat transfer to the carb.

 

What was the timing?

Pinging is exactly what happens when it is too lean. (fuel starved)

When the mechanical fuel pump was bad in my z28 you could have drove it to japan and back and not known about it until you went WOT. It started out just happening ever so often and then progressed until every time you went WOT.

You need to at least check the fuel pressure when it's WOT, or when it's malfunctioning, to rule it out.

 

idk aint got no timing marks but I had a single tdc and its pretty far advanced but I aint got the gas to see if Its any better since I retarded it. But I will try and check the pressure soon. I can give it WOT any other time like right after start up or after a car turns off and it does just fine.

 

i have the same problem except my only happens when its under a load and my makes aloud poping noise and i just bought this car and im pretty new at this but i have a little filter in this platic caseing and i figure it should be full with gas well its running but its not its about half and it bubbles like its getting lots of air and no fuel and i didnt state this but the little filter is up by my carb and it goes to my mechanical fuel pump and my timing is apparently dead on so if you figured it out keep me updated

 

Why dont you pick up a cheap timing tab and tape so you know where you are.

 

just in case somebody is having the same issue I will say how I resolved it...
Put on a new pump- no change
rerouted fuel line- slightly better
put on a aluminum spacer- problem solved but carb stud hit hood
Coulda went with a thinner air filter but I had just bought my 14" K&N so I cut a hole in my 91's old hood and put on a shaker scoop from a 2nd gen (not such a good idea since third gens hoods slope much more than 2nd gens, and our motors aint perfectly centered in our cars)
looks great from 20+ feet away