Every engine is different. One might take 30, one might take 25.



Since you’re using the holley, have you verified your timing? Your 27* might actually be 24, or even 30+. They holley has no way to tell if your crankshaft reluctor is in the correct spot. I’ve seen them off quite a bit, mine in particular has to use a 3* timing offset to get it where it needs to be.

Checking the plugs after a pass would be my suggestion. I also peek at the fuel flow numbers in the holley data log to see what timing changes make to fuel flow consumption, assuming all your fuel data is correct in the holley.