idols great, sputters and pops when I give it gas

[C203/4]

I have a 72 chevy 350 just recently tuned it up, points, plugs, duell at 30 timing 8degrees top dead center. adjusted carb was real rich.... three turns in....

Now I have a significant problem, truck will start, idol but when i give it gas it stalls or pops back thru carb, and sometimes it doesnt do it at all. any ideas? is it carb or is it something else, vaccum advance is working good. please help!

battery was low on water, I know old battery could a bad battery have something to do with it???

[larry may]

water in fuel ? point gap too close? starving for fuel? X plug wire? Change fuel filter?

[C203/4]

nope no water in fuel, how do i check point gap? see if ti still is at duell of 30? plug wires are good havent changed fuel filter... would any of these make it run good one day and not the next?

[racin69z]

You may want to check the accelerator pump on the carb. If it was idling rich, then you leaned it out the rich idle could have been hiding a poor pump shot.

[OrangeCrush1970]

I had a bad battery in my truck and it gave me a similar problem, but I did not have any backfire / pop... my truck just would not stay fired. I did not know this but the battery acts like a huge fuse and take all the extra voltage that your ignition is cranking out. May not be your problem, but something to consider. Hope this helps-

[C203/4]

so maybe i should turn the screw back out... and try that ?

[jhow66]

Turn the mixture screws all the in (lightly). Turn each one back out 3and 1/2 turns. 8* BTDC-right?

[wibilly]

take theair cleaner of with engine off look in top of carb while opening throtel to see if accelerator pump is giving it a good shot of fuel. do not try to start it with the air cleaner off, there is no need to burn it yet

[72lb4x4]

How did it run before the tuneup? If it ran better, its something you changed during the tuneup.

I'd guess dwell, timing, or carb adjustment.

Run it at night or in the dark and look for spark where it doesn't belong.

The idle mixture screws are/were at "3 turns in?" Seems like a lot since a fairly typical starting point is 1.5 turns out from where the bottom.

Setting the dwell will set the point gap.

Is the timing 8 degrees advanced, or retarded? Should be advanced and I can't even say if it would or wouldn't idle that retarded...

[C203/4]

Well, tried turning the screws out more, will check dewell again, could i just have received a bad set of points?

[VetteVet]

Good advice from all. Popping back through the intake is almost always a lean condition, or timing too far advanced. Rarely a bad or incorrectly set intake valve will cause it. Compression test or leakdown test is a good diagnosis for that.
Setting dwell will change the static timing, as the points are opened the timing will be advanced. The dwell should be set first and then the static timing.
Here is a good tutorial on points and ignition .
http://abbysenior.com/mechanics/ignition.htm

[dznucks]

check all your wires too. i have had similar problems when i had a burnt wire.
make sure that the wires arent damaged around your exhaust manifolds. if there is a bad wire the engine will appear to idle fine, but when you rev it up that cylinder will be backfiring.

also when you adjusted the carb you said you adjusted to three turns in. i am not sure what that means or what carb you have. but you should turn the screws in until they are lightly seated and then back them out to their proper setting.
good luck

[89 crew]

Also check the distributer cap for tracking. If you improved spark it might have started a prob.

[Jrromney69]

I'd suggest converting to HEI... In that situation it's better to be "pointless".
And like 72lb4x4 said about looking for spark and what not... But don't look too hard, I've seen a guy lose all his facial hair from that.

[truckdude239]

Originally Posted by racin69z

You may want to check the accelerator pump on the carb. If it was idling rich, then you leaned it out the rich idle could have been hiding a poor pump shot.

[72lb4x4]

Heh! I only suggested opening the hood in the dark and looking for stray arcs--I did't say rub his face on the wires...

I also asked when the problem started and got no answer Waa!

[C203/4]

yea started after a tune up and my father adjusted the carb ' was a mechanic untill the early 90's and had his own tune up business...

[wild4wheels]

Holy crap! I've got the exct same problem on my 71, just had the carb rebuilt and it is acting the same. According to 2 different mechanics it could be the "_____ valley" or " ____ tube" ( I forget what they called it)under the intake manifold that warms up the carb/choke is plugged and cannot heat it, therefore the choke is always on. Not an issue during summer months, just when its cold? Also, timing chain could be an issue as well. Hope that helps, just F.Y. I. local shop wants $400. to remove, clean and re-install the manifold which seems like date rape to me!