Holley 4412 HP

[Robertms]

Has anyone tried the new Holley carb on 2300 dirt cars? If so what do you think of it? Robertms

[Foghorn]

I would like to know also. It looks like a nice piece. I would be interested in how it works on a dyno next to some of the reworked 4412's that different companys are selling. It sounds like they may have solved the old pullover problem for the 4 cylinder crowd. So who is going to "Take One For The Team" and do some testing for us?

[84Dave]

Has anyone had the new 4412HP 2-bbl on the flow bench? Tested at 20.4" (1.5" Hg) of vacuum? It may flow moderately more than the old 4412 with the choke horn? 84Dave

[Headhunter]

Have not been here in a while, I got the chance to look at the primary bowl of a HP carb and if there the same on the 4412 I would give it a 50/50 chance of mitigating the vibration induced pull over. For one there is the baffles in the bowl and there is more room in front of the float in the area I believe the pumping originates from. There is also the added mass of more fuel in the bowl that could help it also. But then again every time I think I understand everything that causes this to happen I find out something new.

[Doug_Guilds]

I saw a post on facebook from Esslinger that they had tested the carb on the dyno and weren't very happy with the AFR numbers.

(Esslinger Engineering) Let's just say that the AFR climbed from 10.8 at the hit to 14.2 by 8,000rpm... Not exactly what you'd want for a reliable tune-up! Our guage legal 4412 stayed between 11.8 at the hit and then 12.2-12.7 all the way to 8,500rpm! Even the C&S Aerosol 4412 keeps the AFR stable in the mid 12's upto 8,500rpm!

[csj1]

I have had this carb on the dyno for well over a week and can’t seem to get it to work. Starts off way too rich and bogs the motor down but once it picks up around 3500 RPM leans out. Just pulled it off, going back to the original carb for the rest of the season. I will mess with it again over the winter. CJ

[R2C Competition Filters]

So far, the new 4412 booster signal has been very erratic in our testing. In an effort to design a base that mitigates entry turbulence and creates a more consistent pressure/velocity over the booster, we've found it requires much more CFD analysis and testing than the 4412 with choke tower required.

[oilman]

For what it's worth, I know 2 people who tried HP carbs on a V-8 and both of them ended up taking them off. They just don't run right. Both were done by well known carb builders.

[car62]

not sure what the difference is, but we run the new 4412 XP and it works great on a 2300

[7uptruckracer]

Just got the 4412XP didn't have to change a thing was imaculate on the dyno

[Robertms]

I understand there are some metering plates that are being produced that really help this carb.

[scott5104]

+ One to Holley Ultra XP - was having all kinds of issues with 7448 Holley, did/modified everything that anyone listed here. 1/4 mile dirt 6 degree banking, bolted on the Ultra and set lap record 3 times in feature. Didn't touch anything...

[car62]

when they discontinued the HP and replaced it with the XP it seems to have corrected alot of issues,the XP carb is so much more responsive than the HP on the exact same engine with same jets and PV block