Holley 4412 Needle and Seat Question

[BC1]

What is the recommended needle and seat size for a 4412 on gas?

[sj valley dave]

I think our Willy's 4412 had a .110 Viton needle and seat

[dynoman14]

BC1;

.110" should flow enough fuel for 500HP, if you have adequate pump, fuel pressure and line size.

More HP than that you need to move up a size. Usually about 4-7psi is what I run. Some folks run more but I don't like the possible over aeration of the fuel at higher pressures. I used to run 4-5psi on 800HP ARCA engines and never had a problem. Most of the carb parts were BLP or Braswell and I ran larger Titanium needles and seats, just my way of ensuring I kept the bowls full.

I also like a weighted float in my 4412's ( maybe 18-22 grams ) and a spring loaded needle and seat. If you can't find them I keep both of them in stock. There are a couple major things that need to happen in the metering block if you want them to run right and not pull fuel over thru the boosters under deceleration. I keep them on the shelf also. It is real nice if you start off with a Keith Dorton model as the metering block has 5 adjustable bleeds in the jet well, that you can tune with and tunable PV openings.

[50j]

The dorton 500 has 3 and doesn't have the adjustable block. The dorton 350 does.

BC1;

.110" should flow enough fuel for 500HP, if you have adequate pump, fuel pressure and line size.

More HP than that you need to move up a size. Usually about 4-7psi is what I run. Some folks run more but I don't like the possible over aeration of the fuel at higher pressures. I used to run 4-5psi on 800HP ARCA engines and never had a problem. Most of the carb parts were BLP or Braswell and I ran larger Titanium needles and seats, just my way of ensuring I kept the bowls full.

I also like a weighted float in my 4412's ( maybe 18-22 grams ) and a spring loaded needle and seat. If you can't find them I keep both of them in stock. There are a couple major things that need to happen in the metering block if you want them to run right and not pull fuel over thru the boosters under deceleration. I keep them on the shelf also. It is real nice if you start off with a Keith Dorton model as the metering block has 5 adjustable bleeds in the jet well, that you can tune with and tunable PV openings.

[dynoman14]

Oops did I give away another secret ???

My Dorton 4412HP's are delivered with 5 adjustable emulsion bleeds if the rules don't specify otherwise.

[50j]

That's ridiculous. Just say "OOPS, I made a mistake". You're not fooling anyone.