engine prob

[Ackattack]

Ok, I need a little help here

Sometimes when I'm cruising along at say 1/4 throttle, and then gun it to say 3/4 to full throttle, my truck will do something weird. It sounds like to me maybe it backfires through the carb, but i'm not sure. It kind make this weird noise like it didn't fire and will loose power, then when I let off it will continue to drive fine. It mainly does this when it's not quite up to full operating temp.

Does anyone know what it could be? I'm thinking either distributor/timing or carb. It has done it with both the 600 edelbrock and 600 holley I've had on it though.

It's kinda hard to describe exactly what it is in words..but hopefully someone can help.

[jef5150]

i was gonna say choke,but you say it does it with 2 different carbs,,,,,maybe intake manifold leak.while the truck it idleing,take some carb cleaner and lightly spray it around the edges of the intake mainfold,,,,,if the rpm rises you have an intake leak,,,,,try it,then you can eliminate that as a problem,,,,,,,,jeff

[D.PASSMORE]

Probaly sucking air around carb on manifold.

[Class of 69]

Is the choke operational? If not, that could cause the symptom you describe. After that, I second a vacumm leak.

[griesel72]

Off topic, but Ackattack, did i see you in aggieville saturday? it was about 2:00 pm and i think that you were directly behind me. That is a pretty sharp truck you have there.

David

[Ackattack]

Choke on one carb is manual and was open, and the other is working just fine. I'll check for a leak.

Yeah, I was in Aggieville...had to try out Jimmie Johns. Were you in one of your 67-72s?

[Ackattack]

no vacuum leak around the intake or carb.

Any other suggestions?

[1972chevy4x4]

I had a similar problem on my old drag car with a big block chevy. It would heisitate and make a kinda coughing sound and then take off. I had to adjust the vac. advance on the distributor and she took off like a stripped a**ed ape. Hope this helps somewhat.

[COBALT]

I was just going to say...you might want to check timing. Too much advance can do some wierd things. Same with a retarded state of timing.

What's the mark on the balancer say when you've got the vacuum advance plugged, and the timing light on?

[Ackattack]

Well I figured it out. The timing was WAY off. I got that fixed, but it created another problem.

I did a little research on the net about engine timing. Basically I'm trying run as much advance as possible without pinging.

Well now I'm having starting problems. The starter's not strong enough to turn over the engine.

On the good side though, I picked up a ton of low end torque, throttle response, and the sputtering and backfiring is gone.

When I first checked the timing it was at like 4* ATDC!!!!
I now have it set at about 10* initial.