stupid carb question/problem

[Moose]

i've got an edelbrock 400 bolted onto an edelbrock 1400 in my '78 bronco w/a 6.6L engine. the problem started as soon as the weather got warmer last month (so the old people say), after i went through my first tank of premium gas w/OUT a lead additive, and after installing a new set of rebuilt heads w/new hardened valve seats. as soon as i filled the tank with gas and an STP lead additive, at idle in drive, the engine would stutter. rpm got real low like it wasn't getting enough fuel. stalled a couple times. won't stall as long as i keep my right foot on the gas, and left foot on the brake. driving, it does fine, unless i'm going under 25 mph.

one afternoon of frustration, i floored it, the stutter went away. that evening i drove it 25 miles, no problems. then it started again the next day. had a guy from work that knew about carbs re-adjust it, fixed the stutter again. that was a month ago, no problems since then. same tank of gas. this morning, tried to drive it to work, started stuttering again.

i was told:

1) maybe the lead additive burned the fuel pump diaphram

2) the fuel filter was dirty (replaced, nothing changed)

3) unscrew the two idle adjustment screws in the front, spray carb cleaner in there and blow it out with compressed air, and pull a couple star bolts on the top and spray carb cleaner in there too

4) i got water in my gas; use "dry gas" or "heet"

5) vapor lock; loosen fuel cap (this could be an option since every time i top the tank off, this happens, and it usually goes away after i drive it a couple miles. and it's the original gas cap)

6) not enough fuel pressure (if so, then why does it come back alive every other time)

7) sending unit strainer clogged

and don't tell me to trash the edelbrock carb. it's run in this truck for a year, no problems.

[jerryg79]

is the carb 400cfm, I ran a 650 4barrel on my 351M, is that 2-barrel or some ****. Why are you using lead additive, I never used it on mine, it seems like you like to waste your money on extraneous things.

Have you thought about rejetting it, I always needed to do that, mine would backfire through the carb, if you really got on it.

I think it was James that used to get Vapor Lock real bad on his 400, i think he routed the fuel line way out around the motor to keep it out of the heat.

I'm assuming you did away with the mechanical fuel pump?

[mudtoy67]

Why are you running lead? Very high compression? The only people I see running lead are race cars running race fuel. The race fuel has a lot more octane than regular gas. I'm wondering if adding lead to regular gas may be causing some of the problem.

[stx4wheeler]

a two barrel will run fine on that motor cause thats what im running in the 7.5L, i would think as well that it is the lead additive messing something up, as jerry said is the fuel pump electirc or manual if manual your pump could be trashed.

[jerryg79]

a two barrel will run fine on that motor cause thats what im running in the 7.5L,

What is the world coming to when we use YOUR Bronco to guage what will and will not work......

[BMFScout]

I think the solution is for you to sell me the camaro...cheap.

If you put in hardened exhaust seats, I don't understand the lead additive, not necessary. I say it's the carb, but heck if I know what's wrong.

Helpful as always Fred, what a d!ck...

[Moose]

is the carb 400cfm, I ran a 650 4barrel on my 351M, is that 2-barrel or some ****. Why are you using lead additive, I never used it on mine, it seems like you like to waste your money on extraneous things.

Have you thought about rejetting it, I always needed to do that, mine would backfire through the carb, if you really got on it.

I think it was James that used to get Vapor Lock real bad on his 400, i think he routed the fuel line way out around the motor to keep it out of the heat.

I'm assuming you did away with the mechanical fuel pump?

thanks for the reply jerry,

the carb is a 600 cfm 4bl edelbrock.

well, the machine shop told me to... sort of. before i rebuilt the heads for the 2nd time, the valvetrain went to shat. i brought them to him, and he told me he just put regular seats in there, and i should have used a lead additive (i didn't know that). so he rebuilt them for nothing the second time with hardened seats and said now i won't need a lead additive. but because of the lack of an additive the first time, i'm phobic w/out it. so i asked if i could still use the addititve with the hardened seats. he told me it wouldn't hurt, if anything it will help.

why would i do away with the mechanical fuel pump? the heads were only ported around the exhaust seats to allow for a little more fuel/air to go around the valve when openned. the chambers and cam are stock size.

[Moose]

Why are you running lead? Very high compression? The only people I see running lead are race cars running race fuel. The race fuel has a lot more octane than regular gas. I'm wondering if adding lead to regular gas may be causing some of the problem.

bryan,

lead: see above post.

i'm starting to think maybe the additive is causing the problem. i'll call the machine shop and see what he says.

[jerryg79]

Maybe I'm dumb, if you have a mechanical fuel pump, you dont have a sending unit do you? I thought that was for electrical in-tank fuel pumps. I thought the whole unit for a mechanical fuel pump was attached to the side of the block minus an in-line filter. Hence the vapor lock. Maybe I'm wrong.

[Moose]

a two barrel will run fine on that motor cause thats what im running in the 7.5L, i would think as well that it is the lead additive messing something up, as jerry said is the fuel pump electirc or manual if manual your pump could be trashed.

kevin,

it actually does pretty good on gas. performance is good. i'm gonna leave well enough alone.

i'll try to replace the fuel pump this weekend.

[73bronco]

sounds like the carb isnt adjusted right to me. try swaping another carb on and see how she runs

[stx4wheeler]

kevin,

it actually does pretty good on gas. performance is good. i'm gonna leave well enough alone.

i'll try to replace the fuel pump this weekend.

the first part of my reply was for jery when asking if it was a two barrel or four,
i dont have that much of a performance motor either and i would run an electric pump on it, it isnta whole lot more expensive(orieley brand) than a mechanical, and i noticed alot better starting(after periods of the truck setting a couple weeks) and a little better running when i went from mechanical to electric. plus it was pretty dang easy to install.
if you need i can get you the part # of my electric pump if you wanna go that route. good luck man

[agjohn02]

Maybe I'm dumb, if you have a mechanical fuel pump, you dont have a sending unit do you? I thought that was for electrical in-tank fuel pumps. I thought the whole unit for a mechanical fuel pump was attached to the side of the block minus an in-line filter. Hence the vapor lock. Maybe I'm wrong.

its the thing in the tank with the fuel gauge on it. it "sends" to the gauge. its also got a sock on it for filtration.

[fbronco86]

get fuel injection

[robertf03]

don't need no gas