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Chris Rosell

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Been on the site before, decided to get more involved in my love of mechanical expertise! Current and lifelong project so far has been a 70 Chevy C-20 Pick up. I have had lots of luck doing repairs myself, learning the technology along the way also doing modifications to run everyday ethanol.

Looking for clues on how to take a stumble out of my motor at 2500 to 2900 rpm. Will poke around and see what I can find out. Looking forward to getting er done!
 
Welcome. Post your engine build specs.
Do you think the stumble is from the ignition, or fuel, or something else?
 
Been through the HEI ignition fairly well. Disconnected the Vacuum Advance, base timing is at 14 btdc. Motor is Gen 1 mostly stock, 441 heads, comp cam 1 step over stock, Edelbrock 1405 manual choked carb, stock intake. 70 K on motor, has good vac at idle, in gear it drops to 17 to 18, in park its well in 22.

Vac gauge reveals possible low compression due to rings, rev in park reveals drop to zero then up to 25, then down to 22. Heads were redone 70 k ago along with complete top end. I am inclined to believe the bottom is going, especially the rings. I have yet to pull the plugs and do a compression test. Still runs, Ha! I am scared to get the real facts! Its still running!
 
Most likely ignition related.
Spark plugs.
Pull and check.
Post pictures of them. So we can read them with you.
Do a Cranking compression test on all 8 cylinders.
Likely OK but check still.

The Power pistons primary side of the Edelbrock carb, remove & check.
The pistons themselves may be scratched up.
Polish with 600-800 grit sandpaper.
Wrong power piston springs or calibration will cause hard to find stumble issue.
 
and hooking up an accurate fuel pressure gauge to the carb inlet fuel line ,
to verify consistent fuel pressure,and checking and setting the float levels would be a good place to check.
you'll waste far less time and money in the long run,
if your carefully isolating, problems and dealing with verified facts,
rather than guessing,or dealing with the results of ignoring the issues
 
Welcome to the forum !!! Always nice to see a new person join us!

More detail about the stumble. Does it happen when you go WOT, or just a very easy application
of the throttle .... or ..... ???? Describe the situation in detail.
 
Just an early guess here, but I think you might need to take a can of carb cleaner and
flush out ALL the passages in your 1405 Edelbrock carb. It's easy to do.
 
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