okay here the deal 540 cu in 10.4.1 comp 647 lift holley hp 950 modified to 1040 cfm what jets to use for safe fire up for break in run .? dont want it to lean dont want it so rich as to wash the rings. .. thanks

As you probably know 950hp came with 78's all 4 corners and with secondary power valve I find it runs the best with the 78jets just as from the factory! May try plugging and increasing secondary 8-10jets as recommended. Who modified your carb to 1040cfm? Jets were changed at time of modification? Bill Mitchell has 88's squared in his 540's with 1050 Dominators. Sounds like a good strip/occasional strip motor you have there so think perhaps starting with 84jets would be reasonable, towards hot side on plugs. Start and warm engine and then pull #1 plug to check how running. Of course adjust carbs idle/mix screws and floats as needed! Goodluck! :cool:

sent it back to holley for modifications 275 bucks was cheaper then buying a 4500 series carb and intake sent it to them with no jets got it back that way . they enlarged the throttle plates and main body bore changed boosters and some mods to the metering blocks . i was thinking 82-88 so i was close thanks for the response..

A friend had a 496 with an 950HP on it unmodified and he made the most power with 81's square with PV's.

For break in purposes you could be somewhere in that range and not have a single problem. Remember that an engine only runs lean when it's under load(I'm using that term loosely).

All your doing putting it in "park" and running it up to 2000-2500 for break in. It's not under a load and your RPM's aren't that high.

It's more important to get that motor fired up immediately and keep it there as well as keep the temp reasonable.