[My427stang]

Currently you run
- A decent cam and a decent carb
- One of the the worst intakes and possibly the worst heads for peak horsepower

(although no FE heads are horrible, those flow the least by 40+ cfm, meaning their peak hp capability is reduced by 80 hp in a perfectly matchedmotor)

So getting 300 flywheel hp isnt too bad for a basically stock 390 with a cam.

I think you are at about where you should be with what you have, although you may be able to make some minor improvements.

1 - Make sure that air cleaner lid has room and flows enough, it may require cutting the choke horn or changing to a HP/Proform type body. Plus going rich with an air cleaner on it usually mean the air cleaner created a restriction

2 - Dump the Performer 390 intake (its a pig) for a Performer RPM, if you dont have hood clearance, look for a used Edelbrock Streetmaster. If you have room, a 1 inch open spacer will help top end a little too.

3 - Make sure you are getting the throttle completely WOT with the pedal. Lots of times the pedal doesnt open the throttle all the way

Run the same carb, put it back to stock jetting. Something isnt right that you need that much of a change (of course thats assuming you do have a 750, if you post the LIST number off the airhorn we can verify)

Those changes, could get you 20, or it even could get you 40-60, hp depending on how bad your current air cleaner is.

A set of the 72cc chamber Edel heads will give you the next step and should really wake it up at high rpm, with a slight loss of low end (very slight) However, its not worth doing until you get that intake and air cleaner resolved.

However, changing the heads will not be cheap, if you dont run roller rockers, you probably should at that point, to include studs and end stands. The roller rockers are not required, but studs are, and when you start to spin it hard end stands are important too.

If it were mine, I'd fix the air cleaner, change the intake, add a 1/2-1 inch spacer, make sure the timing curve comes all in by 2500 and see where you are.

Then, if it doesnt cut the mustard, go the next step over the winter with a set of heads that flow.