Engine Misfire & Stumble

[toolboxchev]

So I have been pretty lucky with my older rebuilt engine so far, until today.

Going down the road under mild acceleration I get a ever so slight misfire. I have been having a problem with a lifter under cold starts for a while now but it will quite up after running for 10 seconds and after a couple of minutes it is virtually non existant.

Fast forward, under half throttle it is stumbling and a few more backfires I am thinking the HEI ignition module is going out again. I go through one about every 2 years due to the older style of charging system which can give out voltage surges.

Replaced it and I have the same problem, now I thinking I am losing fuel pressure or in need of a fuel pump. Have not checked pressure yet.

What is a good next direction to look at?

Carb is about 9 years old, Eddy, stock mechanical fuel pump (not leaking yet) Large can style fuel filter, I checked between fuel filter and carb by cracking the line open, fuel came spraying out.

HEI was just gone through last fall, new adjustable vac advance, cleaned weights, and made sure springs were functioning ok. Everything was ok until today until that little backfire. Ughh I start a new job tomorrow and this is my driver.

Stumped for now, looking for some hints, Any pointers are appreciated.