fuel problems...carburetor...jetting upgrades

[nimruv1]

well, i thought my car was acting a little odd. was driving to get gas before i run out and sure enough i stop in the middle of the road. found a spot to stash the car, got some gas and proceeded to get moving. turned the key and nothing. put some fuel in the carb and she fired right up. then of course stopped, no more fuel. i pull the fuel line, hit the key and nothing. fuel pump busted. i decided to upgrade to the holley 80 gph. put the new pump in, turn the key and were off. worked great! actually, seems it may be wurking to well. i dont know why but since i put the new pump in the car is acting as if its hesitating while accelerating?? i'm not sure? came to the conclusion that possibly the carb isnt calibrated for the amount of fuel its getting?? i'm not sure though. or maybe the new pump is sucking the line shut somewhere?? if that were the case seems it would have to be before the pump?? anyway, i was considering that i should up the jet size. the carb is a stock 600 cfm holley 4-barrel, probably has a 65 jet or so, i dont know yet. i was at the parts house and just wasn't sure what size to go straight to?? was thinking about going to a 70?? thing is i dont want to buy a bunch of individual jet packs that may not even help, or arent correct and then cant return them either, who does?? also wondering if i should upgrade any other component in the carb while im at?// from my experience, one leads to another. anyone familiar with this, able to help me get it right without too much trouble???
thanx

[Hoonbash]

Just a guess here,check the level of your floats.The fuel should be just below the level of the sight glass(if equipped) or the large flat head screws.

Hoonbash

[chevyart]

check floats first, as the other forum member suggusted. Car should be on level, and then remove metal plugs, if that is what you have, and look at the opening. gas shouls just be barely trickling out of the holes. I would do this one at a time, front first. put a little rag on the side in case the float is too high, as gas will pour out quick. and adjust float as necessary. Holley says to change one jet size at a time, in both front and rear (example 65 to a 67. you may have a meetering plate in the rear, which will prevent you from changing the size there. carbs from the factory are usually righ on in jet size right out of the factory so more than one jet size up is probably too much.. If thew float is stickink, maybe you got dirt caught in the needle and seat. that is easy to clean and reinstall and reset.If your car backfired at all you may have blown out a power valve, or it may not be the right size one. do a vacuum test, car in gear, and whatever your vacuum reads, then put in a power valve half the number ((if vacuum is 10 then put in power valves wikth the number 5.0 or 4.5. if the vacuum reads over 12 then go with a 6.5.. if you have a meetering plate in rear then you will not have a power valve in the rear. could also be a bad fuel pump. drive car up a dig hill and if it runs worse going up the hill it usually means a bad fuel pump. If the car hesitates when you are initially giving it gas it could be a bad accelerator pump, but if its hesitating after the initial gas then it is not that Pinched gas line? good luck Chevy Art

[cosvega76]

What fuel pressure are you running with the new pump? For the street, I wouldn't run any more than 6 or 6-1/2 psi.

Did the car run well before you ran out of gas? If it did, I would look more at cleaning the crap out of the carb that got sucked up from the bottom of the tank and killed your other fuel pump.

Chuck

[nimruv1]

wow...thats a lot of stuff. i will try to go through all that and see what happens. i guess when i said hesitating when accelerating i mislead all. the fuel pump is brand new. i didnt actually run out of gas, i thought i did.. i guess what happened was the fuel pump took a crap. the car had been acting peculiar a day or two before, going down freeway and short hesitation then normal and so on until on my way to get gas car started doing what they do when your running out of gas. hesitate, go, hesitate, go, die!! after figuring out the fuel pump broke and putting the new one in. the car fires up and runs great but seems really strong, responsive in a weird way. new pump is probably wurking so well compared to the one that busted that the car seems weird to me. the hesitation i referred to in my previous post is more like being in a low gear at high rpm all the time throughout every gear. this started after i replaced the stock pump that broke with the new 80 gph holley fuel pump. so i'm still not sure whats going on????

[Astre-mutt]

What fuel pressure are you running with the new pump? For the street, I wouldn't run any more than 6 or 6-1/2 psi.

You did install a fuel regulator with the new pump?

[nimruv1]

astre-mutt

no i did not. i'm not familiar with that part. will incorrect fuel pressure cause a car to act similar to my description?? i'll have to go check the box for pressure. it is a street /strip fuel pump i think around 7psi

[Sirshredalot]

Even without a regulator Id ALWAYS recommend a gauge...theyre cheap and a great diagnosing and tuning aid.

Ive seen pumps that where supposed to put out 6PSI put out closer to 16PSI and visa versa....always good to check.

But to answer your question....Low fuel pressure can cause that as well as floats that are adjusted too low....But too much fuel pressure and it will cough alot more as well as puke gas out of the bowl vents.
It can also run rich and foul plugs.

But it sounds like too much fuel is NOT your problem.

God bless
-Shred

[nimruv1]

the pump i bought specifically says no regulator needed so i figured the pump is not the problem. its a 7.5 psi pump. i dont know what to do. up the jets, power valve? maybe the old pumped was so crappy that the car is running great now and im just not used to it?? if timings right, ignition, air fuel, temp, etc... then there's nothing wrong???? whatever the case, the difference started after installing new fuel pump so thats my only relation to the unfamiliar feeling

[73astregt]

do yourself a favour get a fuel pressure regulator put it in the line between the pump and the carb also get a fuel pressure guage and put it in the line between the regulator and the carb as was said just because it says the pump puts out 6 or 7 psi it doesnt mean its gospal i put an edelbrock mechanical pump on my car that was supposed to put out 6.5 psi same as the carb wanted and after installing a guage i found that it was putting out about 8.5 psi wich can push the needeles off the seats and cause flooding. put the regulator on and adjusted it back to 6.5 psi and all was fine. your final fuel pressure i believe will also be determined by the size of your lines ie: too small, too big. just my thoughts im no expert by far lol. the regulator and guage will at least help you eliminate fuel pressure as a source of troubles and isnt an expensive upgrade i think i paid about 40.00 for a holley regulator and about 30.00 for an autometer guage but thats here in canada your price in the states will probably be a fair bit less than what it cost me here.

[Sirshredalot]

As for a good cheap regulator...Try quickfuel....Ive used theyre regulators before and they where actually cheaper than a Holley.
They where about $22...and a fuel pressure gauge is about another $20-25....Shouldnt need anything fancy...no liquid filled or bypass stuff.

God bless
-Shred

[gt350fme]

Got a new fuel filter?

Sometimes a silly little thing like that can send you off track, just make sure.

[nimruv1]

actually no....i didnt put a new filter in.

[gt350fme]

Hey Nimruv1, any luck yet, just curious, what's your actual pressure and flow rate?

[SWT Racing]

As someone already suggested, reset the float levels in the carburetor. You MUST do this when replacing a fuel pump, especially if you have upgraded to a higher capacity pump. You may find that will cure all your issues. If the new fuel pressure is too high, you will know right away, because you will have to sink the float down futher in the fuel when making the adjustment to be able to keep the needle closed.