[yamahajo]

The motor is a fresh 350 mild street motor, edelbrock carb, msd dist etc...all shoved in an s-10. The motor runs pretty good at idle and cruises good as well, but as soon as you stomp on it, it sputters, backfires and misses... Timing is about 38* total. The carb came off my other race car and worked perfect on it, so i dont think its the carb. could the fuel pump be pumping at low rmps, but loosing suction at high rpms? Any advice will be appreciated!
Thanks, Josh

 

[S10 Racer]

The motor is a fresh 350 mild street motor, edelbrock carb, msd dist etc...all shoved in an s-10. The motor runs pretty good at idle and cruises good as well, but as soon as you stomp on it, it sputters, backfires and misses... Timing is about 38* total. The carb came off my other race car and worked perfect on it, so i dont think its the carb. could the fuel pump be pumping at low rmps, but loosing suction at high rpms? Any advice will be appreciated!
Thanks, Josh

Is it an electric or mechanical fuel pump? Your timing seems to be in the neighborhood of where it should be. I would look at a fuel issue. You need to install a fuel pressure gauge and see what kind of pressure you are running.

 

[yamahajo]

its a mechanical pump, Holley i think...With an edelbrock i should have 5-6PSI correct? Also, I can rev it to the moon in park and its fine, but under a load misses and pops. Still sould like a fuel issue?
Thanks!!!

 

[S10 Racer]

its a mechanical pump, Holley i think...With an edelbrock i should have 5-6PSI correct? Also, I can rev it to the moon in park and its fine, but under a load misses and pops. Still sould like a fuel issue?
Thanks!!!

Yes, 5-6 psi is all you want. Being able to rev it in park but misses under a load could be either a fuel, ignition or vacuum problem. I have a 96 GMC that it got to where it would run fine on a flat road but would start "bucking" when going up a hill. I changed plugs and fixed it. I'm not an expert on Edelbrock carbs cause I've never had any luck with them, I am a Holley fan.

 

[yamahajo]

thats about the only thing I havent tried was the plugs...im leaning more toward an igniton/spark problem, but it could be fuel related as well, Im just lost.
Thanks!

 

[S10 Racer]

thats about the only thing I havent tried was the plugs...im leaning more toward an igniton/spark problem, but it could be fuel related as well, Im just lost.
Thanks!

I would definately check out the plugs and check the gap. What plugs are you running?

 

[yamahajo]

ACdelcos gapped around 35 if i remember correctly...

 

[Jim Rockford]

what carb and what size is it?

 

[yamahajo]

edelbrock 650, or 600 i cant remember of the top of my head. I think its a 1407

 

[Pistonman]

Last time this happened to me the valves were tight. I have found some hyd cams don't like 1 or 3/4 turn. Try backing them off to 1/2 or 1/4 turn past zero lash. ( if you have a hyd cam cranked a full turn past zero)

 

[Gene Neal]

Just a thought ! Sounds like a bad COL that has the secondary wiring gone bad.-----------------Your Friend, Gene Neal

 

[yamahajo]

As far as the valves, i set them at zero last, then 1/2 turn. I may go through and reset them at 1/4 turn past zero. As far as the COL, im not sure i follow you...did you mean coil?
Thanks a ton guys!

 

[T-bucket23]

It sounds like a secondary ignition issue. I would take a hard look at the plug wires, dist cap etc for cracks. Sometimes if you run it in the dark and have a helper put some load on the engine with the foot break applied and the wheels chocked, you MAY see some electrical leakage. The engine is most likely misfiring at idle as well, it is just not as noticeable. If you pull all the plugs you will most likely find one that looks a little different. That should lead you to the offending wire. You also could have a cracked or miss gapped plug.

 

[yamahajo]

I pulled all the plugs, all look simular and nothing out of the ordinary. im going to adjust the valves and replace the plugs and try that...
Thanks!

 

[old76c10]

sounds like a cracked cap to me as well...what part of louisiana you from?

 

[yamahajo]

actually, when i first went to crank the motor, the cap was not completely secured down and a little crooked so the rotor hit the cap a few times before I had time to realize it...This very well could have cracked the cap.?..?.. Im going to change the plugs and do the valves and if thats now it im moving on to the cap. Im from Baton Rouge, LA.
Thanks!!!!

 

[T-bucket23]

I doubt it is valve adjustment. If the rotor hit the cap, I would replace both

 

[yamahajo]

I replaced the plugs and backed the valves off 1/4 turn and it runs perfect!
Thanks!!!