Hi guys. I don't get to do much tuning for 1/4 mile times around here so I'm looking for a shortcut...... imagine that

My 4780-1 came stock with 70/76 jets and so far I've changed it to 70/80. Never ran it stock.
My 440 has run a 12.37 at 110 the way it is but the jetting numbers look lean and the plugs are clean. Since I'll only have 3 or 4 chances to tune at the track I'm looking for the fastest approach to the best full throttle power, not too worried about driveability at the moment.
I was going to put 74's in the front and if it picks up I'd put some 82's or 84's in the back and see how it does.
Which end should I concentrate on, front or back or a little of each?
It's a 509 cammed 440, TM7 single plane intake with a 1 inch spacer, 452 heads and 1-3/4 headers, 3200 stall and 3.91's with 26 inch tires.
ANy thoughts?

Don.

a little of each
close the gap and try 80/86s. your combo is pretty close to a buddies that we ran 82/88s @ Mission on the weekend, although the temp was high and the air density around 2500ft. it ran consistent 11.90s

does it have power valves in it?


Either way I would run it square jetted.

no pv , try 80/80

I used to run 84/84 w/ power valves front and rear on a 509 cammed 440.

72 front with power valve and 80 front blocked.
(I would say no higher than 74/82 front)
85 rear power valve blocked. The front barrels on and 800 are the same as a 750 dp the rear barrels are 1/2 between a 750 and an 850.
I have one I bought in 1977 so done lots of jetting and 72/80 front and 85 rear will be pretty darn close. maybe 74/82 but still 85 rear.

I am using both powervalves. I might throw the 74's in the front on Saturday morning before some time trials and see how it likes them.

Don

jet it square .

with the pv go 74-78 at least .

just my opinion

100% RandyB

Let us know how you do....DAD!!!!

My 800 on a stock 440 ran 50cc pumps 42 squiters 88 jets no P/V ..would not go down the track with stock jets in it. need'ed a touch more jet than that.

Well....... I don't recall exactly why I put 80's in the rear . I think It was a morning run I made a couple years ago and it didn't hurt anything so I left it cause the plugs had looked too light previously.
I tried 74's in the front on Friday night at home and the engine didn't like it even in Neutral, it sputtered until it was really revving. Put the 70's back in and all was good again. I never had a chance to play with the jetting on the weekend, I was fighting some pinging issues so I had to get that sorted out first and I ended up breaking out in the Third round on Sunday by .04 on the brakes. I don't know why the car always gets faster Sunday afternoon but I was taking .05 off my dial every round and still letting up at the top end. So I really didn't accomplish much in the jetting end of things but had fun none the less.
Thanks guys.

Don.

I would think your car could handle 74's with ease. My combo is very close to yours other then I run the MP .557 cam. I use 906 heads and 1-3/4 headers but I do have an 850 DP. I run a front P/V and I have 78's and 86's in mine right now and it loves it. No plug fouling at all as I just put over 100 miles on it this weekend. And thats a great looking Challenger. Ron

Thanks Ron. My 800 is a 4780-1. Must have different sized air bleeds or something. My buddy has a quickfuel 750 on his 351 Ford and it came with 74/84. All I know is it doesn't like more than it has now. Unless I have too much at the back and not enough up front, but I doubt it.

Don.