demoke

I have a 1980 4/speed. The original block was rebuilt as a Stage II Crate engine with 9.5 to 1 Speed Pro hypereutectic pistons, a Comp Cams .500 lift hydraulic roller camshaft, Professional Products Typhoon intake and a 750 CFM Holley Carb. ( Also, installed was a new Ram clutch.) It is pulling 375 HP.
The problem I'm having is some "missing" when I am accelerating in high 3rd gear and high speed in 4th. I have had to change spark plugs before, more than I feel I should. Do I need to change again? I don't have these issues in lower gears. (Does not backfire)
Not a mechanic so will have to have done. I have had the original quadra jet carb rebuilt. Just waiting to have put in. Should I?
From what I have read on different posts, mine seems to be running rich.
Any input is appreciated. Thanks

MelWff

1. What octane gas are you using?
2. Which 750 Holley, what is the list# found on the air horn?
3. Has the carburetor been modified? If modified what has been done?
4. Do you have the stock heads?
5. What manufacturer and number are you using for the spark plugs and what gap are they set for?
6. Are using the stock HEI distributor and has it been recurved?
7. If recurved what is the initial and total timing?

TedH

I would validate the spark advance. Sounds almost like it may be getting a little too much. I have total advance of about 35 degrees at 2500rpm and my engine is set up similarly.

jnb5101

Under high demand marginal plugs will cause a misfire. Consider using a hotter plug, and making sure the rest of the ignition system is up to par.