74 gmc 350 start dies

[mikes74gmc]

New hope this is the right place.

 

Driving down the freeway at 70 mph running great then 3 backfires through carb dies tow home.

 What I have done.

 

 

Rebuild Edelbrock 65o set float levels air fuel 1 1/2 turns out squirts fuel ok fuel pump and pressure ok

timing set to TDC on compression stroke rotor pointing at #1. Power to  HEI elect and choke with 1/8th inch open cold normal when running idle 900 rpm crank to start rotate dist clock and counterclockwise. New battery, plugs, wires, fuel filter. cleaned cap and rotor. spark and fuel ok

The engine cranks OK tries to start then dies during crank it is normal then lugs down to almost stops for a sec then cranks ok again tries to start catches then dies.

 I am going to pull the valve covers and check it out. I built this engine and the whole truck AND I NEED HELP!

Any ideas on what happened and why the fix does not work?

[garagerog]

Have you replaced the cam?  If not that may be the culprit. That particular era of 350's had a batch of defective cams, if I recollect correctly it's the number 8 exhaust lobe that wears prematurely, the backfire is the clue. Happened to my brother with a 74 Camaro with a 350 and others that I have heard of.

[mikes74gmc]

Well, I just checked the coil and pick up coil. Going out to put the cap back on and see what I get. I was getting a weak spark so I hope this helps. If not the valve covers come off and I will check compression in 8 first.

 

Thanks for the tip.

Mike

[garagerog]

Mike, any luck getting your 350 to run?