chevy 350 problems

[haplis]

so here is the problem, recently replaced the intake manifold. everything went smoothly. go to fire her up and she wont start. timing right,i advance- so throw a little gas down her throat and bingo she fires, running rough but running. so i adjust the timing and she s running great. turn her off and call it a night. go out the next day and now she wont start unless i pour gas into the carb. i checked the fuel lines and filter, there is spark. i even advanced the timing just to see if that would help. still only fires if i pour gas into the carb. i should also say that once i get her to run i have to lightly press on the gas pedal to keep her running. anyone have any ideas, im at a total loss. also im wondering if it might have to do with the idle adjustment on the carb. edelbrock performer 650 cfm

[hfd410]

Fuel pump? Strange things happen....

[truckster]

I'd look for a vacuum leak. The fact that it runs if you add gas makes me think it's running lean.

[pdawg]

Just a quick suggestion to check the accelerator pump in the carb - with the engine off manually throttle it while looking down the primaries. There should be a good shot of gasoline when you do that. Does the truck bog if you don't feather the throttle when you do get it started? It may be too rich or too lean. Is the carb new or did you have it on the truck previous to the manifold change? Did you reuse the vacuum break solonoid on the new manifold? Too much advance can make it hard to start as well. Sorry I seem to have more questions than solutions.
Posted via Mobile Device

[haplis]

Originally Posted by hfd410

Fuel pump? Strange things happen....

edlebrock performer pump, brand new out of the box.

[haplis]

Originally Posted by truckster

I'd look for a vacuum leak. The fact that it runs if you add gas makes me think it's running lean.

checked the vacuum lines, they all seem to be fine.

[haplis]

Originally Posted by pdawg

Just a quick suggestion to check the accelerator pump in the carb - with the engine off manually throttle it while looking down the primaries. There should be a good shot of gasoline when you do that. Does the truck bog if you don't feather the throttle when you do get it started? It may be too rich or too lean. Is the carb new or did you have it on the truck previous to the manifold change? Did you reuse the vacuum break solonoid on the new manifold? Too much advance can make it hard to start as well. Sorry I seem to have more questions than solutions.
Posted via Mobile Device

i will check the acc pump, the truck will actually bog and die if i dont feather it, the same carb as b4, never had a vacuum break solenoid. thanks to everyone for the ideas

[68 TT]

That really sounds like a big vacuum leak.

Do you have any pics of the intake setup? Maybe we can spot something out of place.

Does your new intake have a square bore, a Q-Jet style spread bore carb setup or one of the hybrid designs that is supposed to fit both? Some don't seal to Edelbrock carbs. They usually supply a steel plate with their new carbs that gets sandwitched between the carb & intake to make them seal properly. You may need one. Make sure you use new carb base gaskets too.

Some intakes have a vacuum port in the #6 intake runner just behind the carb. I have fixed a few new ones that leaked there when the pipe thread boss cracked due to over tightening. I ended up welding the thin side boss edges up and making them thicker to take more load before failure. Same for heater hose bosses.

Do you have power brakes? I had the fitting at the booster separate once and caused a bad vacuum leak. It split in two at the mold parting line and was barely still intact. I had another one that had a two piece design with a snap on top. The snap on top piece failed and fell off. Massive vacuum leak and the engine barely ran.

Did you replace any vacuum hoses from your previous setup? Maybe one of the old hoses cracked and is leaking after being pulled off and put back on. They tend to get brittle over time.

Did you use new intake bolts or the old ones? I got a set of new bolts for one of my engines that were supposed to be application specific and they were too long for the outboard blind holes and bottomed out before they tightened down the intake and the middle couple hit the push rods before the intake.

You didn't mention it so I have to ask, did you use new intake gaskets?

[cdowns]

Originally Posted by haplis

checked the vacuum lines, they all seem to be fine.

vaccume leaks are not only at the lines// carb bases and intake flanges and any gasketed surface of the manifold are places to check

[bonnieclyde100]

if it ran fine befor the intake change i would say vacuum leak between carb and intake probably best bet. a little leak there will really affect vacuum through the carb and keep it from sucking gas during start up.

[68gmsee]

Originally Posted by haplis

so here is the problem, recently replaced the intake manifold. everything went smoothly....

Was it running fine before this? If so, I'd take the intake back off and get a new gasket set. Some of these sets have real cheap, soft end pieces that get compressed out of place so check that carefully. I went through two different sets on my engine recently.

[GMCJOE]

Did you hook up the lines on the fuel pump wrong (mechanical?) Return line to carb and main line to tank. The outlet sizes are usually different on the fuel pump, but hooking them up wrong happens all to often. You also got a chance that your new fuel pump is bad right out of the box, so you might want to pressure test it. Should be 6psi if I remember right.

Definitely check for vacuum leaks, and make sure your linkage components on the carb are working correctly.

[bobs409]

If you can get it to run (idle) spray some carb cleaner along the sides of the intake near the gaskets with it running. If idle picks up, you have a leak there.

Also spray at the carb base for the same.

[GRX]

Originally Posted by bobs409

If you can get it to run (idle) spray some carb cleaner along the sides of the intake near the gaskets with it running. If idle picks up, you have a leak there.

Also spray at the carb base for the same.

^^ x2 ... that's an old trick which works.

[c10srule]

had an edelbroc that did that once, moved the linkage for the pump to a different hole at the pump arm, there are three holes you can put it in, i put it in the bottom hole, also had a vacuum leak on a to baarrel the other day and sprayed it with carb cleaner at the base , revved up, its works great looking for vacuum leaks

[haplis]

thanks for all the input, i will definitely check all the suggestions given and keep you guys posted.

[tim21391]

tap the bowl in front of the carb.. had that problem in mine.. when i had the intake off junk got stirred up and with me tapping with a screw driver fixed the problem haha seems weird but hey worth a shot