I am ready to pull the Holley 750 DP apart, and change the jet size(as per your recomendations here). My question is, how many jets are there? Are there 2 in front and 2 in the rear bowl, or just in the front Bowl? Thanx. scott

two in front...and two in rear.

I have changed the jets to a smaller size. I went down 6 sizes, but now it seems that its starving for gas, and runs worse than it did with the bigger jets.. To small now huh? I had 73 in front and 79 in the rear. Now i have 67 in front and 73 in the rear. What do you think about going back 3 sizes both ways and trying that?

what's the application? I ran 74-80's in a mild 340 w/ 28 squirters and it ran good. 78-84's in a mild 440 w/ 31 squirters.

too lean will also destroy the rings quicker as my uncle just found out in a 302 he just finished building.

6 #'s is alot of change. Splitting the difference(3 sizes)sounds like a practical plan to start with

ok, thanx guys. I will go change them out now, and get back to ya..

I am a novice tuner, but I have some holley experience. Jumping one jet size is not enough to feel but six is kind of extreme. I think three steps at a time is good until you get close. Do you know how to read plugs?

You should have new plugs after your jet change. To check the primary jets turn the car off at cruise and coast to a good spot. Pull a plug and check the color. You want it to be cleanish with some brown tan color. Other colors can be from chemicals in the fuel. Fluffy black is rich a/f oily black is rings or valve seals leaking, look with a loupe or small magnifying glass on the ceramic for tiny metal balls- these would mean it's knocking (pinging, detonation etc.) I like to start rich and go down in jet sizes until it just starts to have a little surging while cruising under load, then go up one or two sizes.

Remember, if you floor it the secondaries come into play- that would effect the readings.

good luck