Hello,
I have a 555 BBC with 10-71 TBS blower. I put on “carburetor” efi utilizing a Holley terminator x and coil near plug set up. Recently I ran into an issue where some of the cylinders are not fireing. I have swapped coils and checked all my grounds but it’s still not fireing on cylinders 1,2,7, and 8.

I am changing the dwell on the spark plug so a timing light works and battery voltage is good. (Also it will start on 4 cylinders and the bad 4 are not getting warm)

any ideas on things to check or try?

Thank you.

Not sure what that could be.. You have a relay for the coils? That wouldn`t explain why only a couple don`t fire however. The cylinder head grounds are important , they have to go to the corresponding head and not have any other grounds attached.
I have 2 Terminator X for sale if needed.
$450 with 02 sensor