weak and hesitant under load

[78 C10]

I have a new motor in my 78 c10. Its a 355 around 10 to 1 compression a set of 487 casting heads that have been milled to the max with tons of other work done to them also. The cam is a comp cams 292 501 magnum cam. The intake is a vic Jr with a 650 eddi performer. Ignition is a HEI with new bosch cap and rotor with brass terminals. Plugs are new and gapped to .045 with new MSD 8.5mm wires. Initial timing is set at 12* and total of 34* at 2700 RPMs.

Cruising at about 2500RPMs I can smash the gas pedal and it will hesitate go and buck like its on and off the throttle a bit. Its like its cutting off the power and then back on. While cruising and normal driving it runs just fine. I have checked everything I can think of from re adjusting valves to plug gap and making sure wires are snapped snugly on to the plugs and cap and I can not get it figured out.

[Mick]

THIS SOUNDS LIKE A CARB PROBLEM. LIKE IT IS DUMPING TO MUCH FUEL INTO THE MOTOR WHEN YOU STOMP ON IT. CAUSES A BOG AND AS THE RPM PICKUP IT GOES AHEAD AND TAKES THE FUEL.

[78 C10]

It doesnt seem to clear up though. I had the same carb un touched on a stock 327 and never had this problem. The new motor in my opinion would need more fuel not less. Could it be caused by a lean secondary condition?

[JES]

Sounds to me like the magnetic pick-up wires are broke in the distributor. Disconect the vac. advance and drive it again and see if problem goes away. I have seen this problem many times on older cars. John Eric.

[78 C10]

vac advance is disconected the problem didnt go away but improved slightly.

[rustbucket]

still sounds like carb. If there is a dead spot right when you stomp it, it may need more fuel. Not sure about edelbrock carbs but with a holley it would suggest the pump shot wasnt big enough.

[78 C10]

I have the accelerator pump set up to squirt as early and as much fuel as it is possible to adjust. Its not just one quick bog and then it goes its on and off kinda like the ignition switch is being turned on and off really fast and never clears up but not quite as drastic.

[JES]

The carb may very well be a problem, if you can barrow a holley or holley style carb this could be a easy way to locate the problem. With the cam you have, it most likely idles rough and the posability that you have a couple of wires crossed might need to be double checked, also is the insulator between the coil and cap in place ? just a few ideas. John Eric.

[78 C10]

I dont have a carb to borrow or exchange for testing. All the wires are in place in the right order I have checked and re checked and had someone else check also. The insulater between the cap and coil is installed. I didnt have time to finish the swap but I am in the middle of installing another known good distributor.

[JES]

Souds as if you have eliminated any electrical problems.try to find a good carb even if it is too big it can tell you a story.keep us posted. I had a problem like this, about 25 years ago, with a single plane intake. Went to a dual plane, same carb and set up and run like it should. You might just need to change the tune on your carb. John Eric.

[supernova]

Sounds like a carb problem!

Those pesky Edlebrock carbs suck! Put a Holley on it and be done with it!!!!!!!!!!!!!

[rustbucket]

Those pesky Edlebrock carbs suck! Put a Holley on it and be done with it!!!!!!!!!!!!!

yep!

[vegaracer]

Sold my Edelborck. Will never go back again.

[Necessary Evil]

I had a edelbrock carb that did the same thing on my 71 torino. While it was idling i looked down the carb and noticed it was dripping bad at idle right out of the squirters, so i took the carb apart and found dirt in the jets and needles. Carb cleaned everything, blew everything out and threw in a rebuild kit then it ran like a champ. But i agree with everyone they are JUNK my Edelbrock was very fussy, one day it ran like a raped ape next day it was a dog, etc.

[wikd69]

I had a edelbrock carb that did the same thing on my 71 torino. While it was idling i looked down the carb and noticed it was dripping bad at idle right out of the squirters, so i took the carb apart and found dirt in the jets and needles. Carb cleaned everything, blew everything out and threw in a rebuild kit then it ran like a champ. But i agree with everyone they are JUNK my Edelbrock was very fussy, one day it ran like a raped ape next day it was a dog, etc.

Note to self: Never go to the zoo with Necessary Evil. Especially not to the monkey section.