Holley experts help

[8door]

Yesterday the truck cools down for about two hours, on restart it will not
stay running at least at idle.Runs fine if throttle is pedaled.
Here is what I have. New factory 350 crate sitting on a Perfomer intake. Dual exhaust , turbo 400. New MDS distributer. New Holley 600.
trans totaly remanufactered.
About 65 miles on the new engine. I'm driving at medium varing speeds 50 -60
cool day 70 degrees go about 20 miles shut it down then after the two hours start and immedialty won't stay running. Nurse it home pedalling the throttle
at stop signs. Keepin an eye on temp that hold staeady at just a tick above normal ( 1/2 way between cold and hot on factory guage).
My first thought is fuel starvation, but ran sweet at 15 mph up to 55.No hesitation good power.
What do I need to check first ?

[Ridgeclimber]

How is your idle speed when hot? Does it have electric choke? If both of those are ok try adjusting your idle mixture screws. Richer it up abit.

[trac209]

Is this a persistent problem after it sits after being driven? Have you checked the gas tank for vapor lock? Open the gas cap if you hear a air rush noise it could be vapor locking and acting up like that I've seen it before. Being a new engine If it's only happened the one time I say you could have a vacuum leak someplace or a lot of different issues.

[chiefcfd]

Check vacuum lines for leak. Maybe a plugged port came off.

[8door]

All three replies are good tips.
Will check all out tomorrow .
I did notice a pressure build up in
gas tank one time, never thought it would affect gas flow.
I did the idle adjustment the first thing, no change.
Electric choke yes, it was open when I adjusted the mixture screws a little.

[geezer#99]

Check your timing too!

[cool68]

for the carb search online at holley.com tech section and/or on Youtube for info on setting choke and choke idle speed and adjusting idle mixture screws. also, make sure that your throttle return spring is truly doing it's job for the primary idle screw to work properly.. post some pics of your engine too.

[ole dollor]

one more thing to check is your float levels. and trash in needle and seat .

[trac209]

My truck was doing a similar thing and when I open the gas cap it blew outta my hand. I drilled a tiny pinhole in it under the lid problem stopped.

[8door]

Originally Posted by geezer#99

Check your timing too!

What I was suprised at was the truck ran to well when I shut it down.
So I'm thinking more along the lines of a rubber part like a vacum hose
poped off. Timing, I'll check it as a routine along loose spark plug wires etc.
Happy New Year.

[zeldman]

Remove the holley, take it to a road construction crew and let them run it over with the big roller. Repeat.

It doesnt sound like a carb problem. As mentioned before, check the rubber fuel lines before the fuel pump. A small, very small crack can allow air to be sucked in and give you all kinds of grief. Dont forget the lines under the cab, and if your tank is still in the cab, check those lines as well.

And also as mentioned before, check for vacuum leaks. If it runs well at speed but not at idle, I would suspect a vacuum leak first. Again, small almost unnoticable cracks can give you major headaches. Check the vacuum line for the brake booster if you have power brakes.


What a great start to the new year for you, it can only get better from here.

[8door]

Originally Posted by trac209

My truck was doing a similar thing and when I open the gas cap it blew outta my hand. I drilled a tiny pinhole in it under the lid problem stopped.

My gas cap has a pressure relief valve, stuck shut. A little puddle of raw gas at base of carb lead me to think pressure build up in the tank.Drilled a pinhole in cap , but haven't checked other things yet ,as soon as that's done I'll let you all know what results are.