Been trying to figure out what's wrong with this thing on my own and I'm about to give up:

At the 3/4 throttle spot I'm getting a sputtering, run-out-of-fuel buck. If I back out of it and ease into it I can sometimes get past it. I can downshift and rev it to the moon no problem, it's getting plenty of fuel.

I have changed the cap, rotor, plugs, checked the vacuum lines, checked vacuum advance with a pump and it's not sticking. I routed all the wires so that none are touching each other. Right now I have distributor advance running off the port below the throttle blades.

I changed the fuel filter and checked the needle and seat. It has a Holley 2280 with some 1984 emission stuff on it. Totally convinced that the carb is the problem, I pulled a perfectly working non-emmision 2280 of my '71 and..............no change!

It's most noticible when the engine is cold. While it's warming up you can hear the odd puff in the exhaust note. The fuel mileage is very good but has gone down a touch lately. It fires up with only one pump and after it's warm it starts with just a tap of the key, so I think the timing is ok and the fuel pump is doing it's job.

I am completely out of ideas, so hope you can help.

Thanks.

A coil will do that

It will, huh? Will it flicker the tach? Not everytime, but the odd time it will spike the needle back and forth.

Was getting a bit of detonation from it too, that's why I checked the vacuum advance......thought maybe it was sticking.

Thanks.


I'll change it out and see what happens next.

Put a new coil in just now.

Same thing. Still sputtering and coughing at 3/4 throttle.

It might rev to the moon as you say in a lower gear but fuel demand and vacuum is higher in the higher gear. You are just guessing unless you have a fuel pressure gauge. I have a HP carter mechanical on my car now that is weak, very weak, but does pump. Change the fuel pump.

Thanks, Crizila, scroll up a bit: I did change the emission 2280 for a '71 2280 and it didn't change it. You and I are thinking alike, 'cause I was sure that would fix it. The non-emission carb did up the power a touch.

Hot 340: I had kinda considered the fuel pump but ruled it out when I could wind it up to 110 mph in top gear without a problem.

I dunno, maybe I'll pull the fuel filter off, blow it out, and blow some air back to fuel tank and stir it up a bit. If that doesn't help I have another fuel pump laying around here and I'll throw it on.

Might be a bunch of crap in the tank at the pick-up, who knows.

It's this basic stuff that drives me bonkers: I can recite a small block stroker build-up from memory but can't get a stinkin' 318 beater sorted out.

Yesterday pulled the new fuel filter off, blew it out, nothing inside. Blew the supply line to the fuel tank out, no obstruction at all.

Test drive: still doing it.

Today tried a new ECU: still doing it.
Put a new fuel pump on: still doing it.
Covered the intake and all vacuum sources with ether: slight rpm change at the EGR valve. Had the EGR unplugged anyway, but pulled the valve off and made a block-off for it.

Still doing it.

Base timing is at 14 degrees, emission label calls for 12. Truck starts perfect so no changes to timing made. Tested with and without vacuum advance and everything is working like it should.

Put the old carb back on since there is nothing wrong with it.

Still coughing and sputtering.

Any more ideas?

Did you check for wobble in the distributor? Also check the gap in there, it should be .008.

I have a similar issue, but narrowed it down to low voltage at the coil, only 4 volts or so. It is wiring between the bulkhead connector and the ignition switch. Still need to figure it out...
So check the voltage at the coil, should be ~10 volts with ballast resistor in place.

Ive had bad plug wires do the same thing under a load but run great otherwise.

I've sort of ruled out electrical because all I have to do is work the pedal a bit and can make it dissappear. Seems to be more of a vacuum/shortage of fuel issue.

Easiest way to get it to act up is in top gear at 1100rpm: hold the pedal quarter throttle and it powers up slowly no problem. Put it down to 3/4 and then it starts.........if that helps narrow it down for you guys.

Have you sprayed the intake and base of the carb with
carb cleaner for a vac leak... it does have a sound
of it being super lean

Yes, I soaked it down with ether everywhere including the power brake booster. Slight change at the EGR valve but it was unplugged anyway. Made a full block-off for it so it's out of the picture. Idle rpm is rock steady too.

The '71 2280 I swapped on did the same thing. That carb came off my '71 Challenger and it gives no hiccups at all.

Can you load it up and do it while standing still...
if so have someone pull 1 plug wire at a time and
see which cyl is acting up... then check that cyl
compression, wire, plug