I'm guessing #75 jets in the rear of a 750 double pumper w/o a powervalve is a little lean for a 454?
Just curious,as I recently swapped a metering block into my 3310 with #80's in the rear and no powervalve..previous was stock metering plate.
I ask the question since I've run both these carbs at the track,and the 3310 was always 1 full MPH quicker than 4779..even though the metering plate of the 3310 is roughly equal to 74/45 jet size (.081-thanks Brandon)
I'm obviolsy on the quest to up my 103.9 MPH..hoping the recent swap to the metering block/#80 jets will maybe get me into the 105 MPH zone.If it works out well with the 3310,think I'll pick up some 80's for the 4779 and try that carb out again at the track.

When I converted my 3310 to a metering block in my 427 I had 84's in the rear. Allthough mine was more of a strip car, it still seemed a tad lean.

I don't have my Holley book in front of me, but doesn't the metering plate have some sort of provision to "bypass" itself to deliver more fuel? Where as the block normally has the PV to take over this function in the event of WOT.

My 950 had 78's with PVs for the strip but my 3310 had 84's with no PV. Go figure.

I think your on the right track, but only tried and true seat time and jet changes while recording the weather will tell.

I'm sure you already know this, but make sure you do a minimum of 3 runs befor you start to change those jets for a good baseline.

Rob

I have 78/80's in the hp950 with power valves,might have to step up the front to 80 also with additional cubes. The 80's sound about right with no power valve. I think my carb will be a tad small now for max performance but still has great drivability.

Chris

i think you might find the 3310 may want a little more jet in the rear than 80s without a powervalve. a 3310-1(4150) came with 76s in the back with a powervalve, going by the old rule of stepping up 8-10 jet sizes when blocking a PV that would put you at 83-85.

like i mentioned before in your previous post, ive got 73/80s in my 3310-1 with front and rear PVs. so i definitely think you could use more than 80s in the rear without a sec pv

looking through my book none of the 4779 list carbs (750dp) have a secondary PV. the 4779 has 75/76s and the 4779-1 and -2 have 70/80 jetting. im sure the same jetting combo used for the 3310 would work fine with the double pumper, but with the DP you probably would be better off squaring up the jetting front to back, like the 78-80 Bob mentioned.

Chris, I will be interested in where this heads for you. I am inclined to believe I am facing a similiar situation with my 770 Avenger. I know it has 72/75 jetting and a 6.5 powervalve. Don't know for sure, but I think it does not have a secondary power valve. I am thinking maybe 74/78 combo with the 408 motor.

Guys,thanks for all the input as always.
I'll run the 80's at the track and see where the MPH goes and post my findings.

Just need to search out some good combination snow tire / drag radials and you will be good to go.

Originally posted by GRN69CHV:
Just need to search out some good combination snow tire / drag radials and you will be good to go. Joe..LOL
Raceway Park opens 2/26
I'll probably just wait until LVD opens in April/May

My 4150 with blocked PV 78front-86 rear ,GOOD Luck

I can remember going to the SnowBird early season sessions at the Grove many years ago.

I assume this is the car with 2.56s? There is a good chance it really doesn't need the full 750 at your trap speed. The vacuum carb is not fully open thus the gain in MPH. Oval port motor? if so they need much less jet than the big port motor that the 3310 came on.

Originally posted by Mike Feudo:
I assume this is the car with 2.56s? There is a good chance it really doesn't need the full 750 at your trap speed. The vacuum carb is not fully open thus the gain in MPH. Oval port motor? if so they need much less jet than the big port motor that the 3310 came on. I have 3.31's now Mike
I shift @ 5500
cross stripe at about 5K/at almost 104 MPH

The 2 Holley 4779's that I had came with 70'sfrt 80rear when new and almost always needed to go richer in a 396 cuber.
75's in the back is very lean with no power valve.