When trying to start my 390 for the first time i had issues with gas shooting back out of the carb. The truck starts to run then dies while mists of fuel shoot out of the carb the it steams. I have replaced the carb with a known working carb so i know there is no issues with floats being stuck. The timing is not 180'ed and is set 6 degrees advanced. Any ideas?

 

I would check floats, needle and seat, and power valve if holley or ford. That 6 degrees is far old ladys crusing, but not your issue.

 

What fuel pump are you using? Is this a newly rebuilt engine you're trying to get running, and did the old engine run OK before the rebuild? New fuel pump? etc. etc.

 

the old lady cruising is just so i can break it in and its new everything. Carter fuel pump. and it ran before i rebuilt it.

 

maybe check fuel pressure from pump hopefully 5-7 psi, prolly long shot.

 

Bought a datsun pickup for a $100 bucks. It had the head gasket replaced and wouldn't run after that. It shot fuel out of the carb. It ended up being a couple of links off on the timing chain. What I am trying to say is maybe check your timing again. I had a mc 2100 and One time I forgot to put the float retainer around the needle and it shot gas everywhere.

 

As unfortunate as it might be, I agree the timing chain might be a tooth or two off, but I'd play with the ignition timing a bit first.

At 6 degrees timing, your intake manifold vacuum will be low. I remember when I was tinkering with mine, I had around 10 inHg at 10 degrees initial timing at idle, and it went up to about 16 inHg with intial timing set at 20 degrees.

This might be easy to check. With the engine running, try increasing the rpms a bit and see if the fuel backspray stops as the mechanical advance increases the ignition timing. Or just loosen teh distributor and rotate it a bit to advacne the timing. Don' drive that way as the dist will have to be internaly adjusted to compensate first.

If it does go away, you might want to consider increasing your intial timing, but make sure the distributor is internally adjusted to maintain the max advance (less overall mech advance range inside the dist).

The other thought with low ignition timing is that the carb has to be set richer, so there is more fuel present, plus the butterflies are probably open more exposing some fo the transition slot.

It's only a guess, and possibly a bad one, but I like to try the easy stuff first. But as it ran fine before the rebuild, it's probably the cam timing.

Checking the cam chain timing is fairly easy, but just a big mess as you have to drain coolant and remove the waterpump to get to the chain cover, plus the headache of sealing it again where it meets the oil pan (unless you take the oil pan off too).

By the way, did you re-use the lifters? Valve lash in solid lifters, or a stuck hyd lifter might be keeping a valve from closing all the way. Can you hear any odd sounds when it's idling?

This is the second time I've heard of this in two days, but I can't say it ever happened to me. Maybe it has and I never noticed as the air breather is usually installed when I tinker.

 

That so called steam coming out of the carb is a valve being open when it shouldn't be. I also say timing wether at the distributor or chain. More than likely at the chain.

 

One possible way to check the chain without taking it apart:

Pull the cap. Rotate the engine. Note where the rotor stops.

Reverse the rotation. Note how many degrees of crank rotation you get before the rotor moves.

One fellow though 5 degrees would be the limit. Not sure, but I'd guess you would be far beyond that if it was loose enough to jump a tooth.

 

Engine was just rebuilt. Would have to be assembled 1 tooth off. Loose chain shouldn't be an issue with a new chain.

 

Ooops, see that now in the op. Back to reading retention class....

 

Stupid me!, went back to work on the truck today, took the top of the carb off, everything looked good. Put it back together, then realized i screw my plug wires up on the cap. A minute later with everything the right way, the truck started right up.

 

Great that you reported back... it's the actual solution that's helpful. Your first post was in April... been down since then?