Need help with sputtering/stalling truck

[Jobe72]

I have a 1972 GMC Sierra with the stock 350/350 and 3.73 gears.
The truck ran great when I got it back in March up until a month ago.
Truck already had a MSD HEI installed.

All I did when I got the truck was replace the carb with a Edelbrock 1406.

One day the truck just started sputtering under 1/2 to full throttle. No changes were made. So I checked the fuel filter and it was clean(has a pretty new tank). Took the carb off and cleaned it out really good (it was clean). Changed the fuel pump out (what a pain in the ass). Changed the plugs and wires. Checked the cap and rotor. It all looks good but the problem persists and makes the truck pretty much undriveable. Truck starts and idles fine, then get on the gas and it sputters along and sometimes stalls out until I back off on the throttle.

Any thoughts?

[blime81]

How do the plugs look?

How far out are the two screws on the front of your carb? IIRC they should be about 2 full turns out.

[blime81]

Oh yeah you didn't mention timing. What do you have that set at?

[Jobe72]

More info...

I pulled the old plugs and they were all super clean, no oil, no damage looked good.
Air mix screws are 2.5 turns out...been that way since I installed it.
Timing I believe is 8 degrees BTDC with it being about 32 at 3,000 RPM's

[red71cheyenne]

Where did you get the fuel pump? Reason I ask, is my last new one from Autozone crapped out after less than a year. Put the old used one from the 71 on and it ran 100% better. I have the same Edelbrock carb.

[Jobe72]

The fuel pump that was on the truck was less than a year old, replaced with one from O-Reilly's but that didn't change a thing...same problem.

It feels like a fuel delivery problem to me but I can't figure out what it could be, like the secondaries aren't opening but they seem to function just fine.

I hate to do it, but might have to take it to a mechanic soon, I need the truck to be up and running to move stuff by this weekend.

Thanks.

[cdowns]

disconnect fuel line to carb put in jar crank engine for 30seconds the spec is about 1pint in that time

you could have the fuel strainer in the tank clogged up

make sure and check for proper wiring of the HEI if they used the original resistance type wire the lovoltage could have damaged the module and need rewiring and replacing the module

[Jobe72]

Anyone else have thoughts? Thanks.

[Jobe72]

Ok, I just checked and it looks like the stock wiring was used on the HEI. Now my question is why would it work for a year and then act up? And wouldn't it not work at all with a bad module? Thanks again.

[aintmisbehavinn]

Don't feel bad, I have the same truck with a holly, I think it is either ignition or stranner. Going for a cap and button tomorrow to go with the MSD 8137 and the 6AL box. I simply removed my Dist cap today, put it back on and now it won't start. As soon as I would hit 4K, it mixes everything up and drops to idle then recovers. (This truck just came out of an 8 year storage, turn key cranked, been driving for days. Big ass ACDelco fuel pump seems to be doing it's job looking thru glass filter. This is driving me crazy.

[Jobe72]

Ends up it was a bad distributor! Pulled the MSD Street Fire and put a GM Delco HEI and the problem went away. MSD is sending me a new module to see if that will fix it at least.

At least I took care of alot of other things I had planned on doing anyway!

[Sinister]

Originally Posted by Jobe72

Ok, I just checked and it looks like the stock wiring was used on the HEI. Now my question is why would it work for a year and then act up? And wouldn't it not work at all with a bad module? Thanks again.

The stock wiring has a resistance wire that goes to the stock points distributor. If this wire is used it'll mess the HEI module up.