android91chevy

well to start off my engine will start and then usualy idle high for mabey 10-20 sec and then shut off. Ive tried messing with the timimg and carb a bunchhh and nothing seems to help...any ideas??

heres the set up:
355 w/flat tops, 64cc/197 al. heads w/ 1.5 rollers, air gap intake, 750 speed demon carb, and comp cams 282 hyd. roller .510/.520 lift, 282/288 duration230/236 duration @ 50

thanks for any help!
-andy

TooLateVTEC

iTrader: (2)

Whats the timing set at?

When did it start doing this? Have you done any work to it recently or is this a brand new motor, or what?

android91chevy

well i set the base timing at bout 12, and yes it is a brand new motor, sry should have stated that

TooLateVTEC

iTrader: (2)

If you try to hold the RPM's up at around 3000 even does it still cut off?

Does it stumble at all or does it cut clean off like you turned the key?

BTW, whats this motor in? lol

android91chevy

yes i tried holding the gas at about 3000 and it still cut off, just like i turn the key off, and even if i pump the gas its like im not even doing it cause it still shuts right off

the motor is in a 91 c1500 short bed single cab

TooLateVTEC

iTrader: (2)

Was there a fuel injected motor in it before and you switched it to carb?

What distributor are you running? HEI? If its HEI, where did you get 12V power from?

Sounds to me like something is cutting off the power to the dizzy man.

android91chevy

yes it was tbi originally, but i had already had a carb motor in it before this engine...and everything worked fine, i do have an HEI hooked up to a msd 6al box

as far as i know i hooked up everything how it was before, i duno its frustrating lol i just wana drive it!

TooLateVTEC

iTrader: (2)

Try getting someone to hold a test light on the power wire going to the HEI while it running and see if it goes off as the motor dies. If it does, might try bypassing the MSD box and wire 12V right to the HEI and try it.

android91chevy

arite ill deff give that a shot thanks

also there is 3 wires that plug in to the dist. cap...if they are wired wrong(which i dont think they are) could that mabey cause this?...one is a ground but im pretty sure its grounded good

TooLateVTEC

iTrader: (2)

In an HEI cap, theres a 12V hot wire, a ground wire, and a tach wire. Colors should be red,black and white for the tach I believe.

The way its cutting off clean, its something electrical.

Wheres the 6A box getting power from? It should have 2 red wires, one big one for straight to the positive side of the battery or the starter itself where the battery cable is and also one for switched 12V...which means getting power only when the key is on.

android91chevy

yes its connected to the battery....mabey a wire has come loose that i have not seen

would the motor still start if it was not hooked up? or would it just not spark at all and just crank?

android91chevy

ok well ive answered my own question, i just unpluged the three wires and it did not spark at all and didnt start. so now i guess ill get a buddy and have him hold a test light while its running and see what happens from there. if it still does have power when the engine shuts off, what should i look for next?

fleetmgr

Vacuum leak...a pretty big one.

android91chevy

really??...all my hoses seem to be ok, where else should i look for a vacuum leak?

fleetmgr

Carb gasket? Intake gaskets? An open vacuum port on the intake, like going to a brake booster? Get some soapy water (with visible foam) and a spray bottle and start spraying the obvious places like this. It should be easy to see it get sucked in if that's the problem.

Have you had the heads milled? If so, did you get the intake flanges milled also? If the heads are milled and you didn't do this, bet that's your problem.

android91chevy

all gaskets are new...i have the brake booster connected to the carb, thats how i had it before when i had a vortec setup.....and if u pull the tube outa the brake booster u can hear air like theres vacuum....could theyre be a spot in the non vortec manifold that you can plug a vacuum hose into that is mabey just open right now?

fleetmgr

You'd have to look and make sure that there are no open holes in the intake. Plug as necessary.

New gaskets doesn't mean that they are sealing.

android91chevy

ya i guess thats true...also if there is a hole on the intake for that then i dont think its plugged so maybe thats the problem...i sure hope its something easy like that

fleetmgr

Just out of curiosity, how old is your brake booster? Have you checked it to make sure the diaphragm isn't gone?

android91chevy

ya the booster is ok, however it is old. but there was an open port in the intake and i plugged that off and did some carb adjusting, and i got it to idle. but its still weird...sometimes itll start right up, sometimes it wont, but it stays at idle for a min or so now and then kind of sputters off....maybe a fuel problem?