SECONDARY HESITATION

[JEFF69Z28]

MY 750 HOLLEY HESITATES A BIT WHEN I FLOOR IT IHAVE BEEN GOING UP IN SHOOTER SIZE AND IT IS GETTING BETTER,IM CONFUSED I STARTED WITH 37 IN REAR AND NOW IM UP TO A 42.SHOULD I BE CHANGING THE FRONT SHOOTER ALSO? :?
MOTOR IS IN 86 SS MONTE CARLO 3550 WITH ME IN IT,CHEVY 406 APPROX.500 TO 525 HP?,3.90 REAR,3400 STALL

[jmarksdragster]

Engine specs? Timing?

[dparker]

Bump your front squirter to a 42 also. You might try screwing out your idle screws a 1/2 turn or so. That will richen your idle alittle. I have also seen that the older 4150s have a solid screw in the squirter. If so get a hollow screw to replace it. That will let more fuel thru more evenly.
good luck

[JEFF69Z28]

I CHANGED BACK TO A 41 ON THE SECONDARY AND WENT UP TO A 35 IN THE PRIMARY THIS TIME IT DIDNT HESITATE,THANKS FOR THE HELP MY CAR RAN 11.92 ALL DAY ON SUNDAY.

[dparker]

You may have to go down a little in the heat of the summer when the air isnt so good. Lots of times theres a 3000ft difference in adjusted altitude form mid summer to fall. When the air is good your idle circuit is a little lean. Thats why you needed more fuel.

[mopar1968]

Jet extenions?

[JEFF69Z28]

I THOUGHT JET EXSTENIONS BUT IT DID IT WHILE IN PARK ON FLAT GROUND ALSO.

[dparker]

I don't know what your timing is set at, but you may be able to bump it up a little to help also.

[mopar1968]

Did you check for vacum leak's? this will cause this because of extra air entering engine.

[fishman1]

Your car weight is 3350 then a 42 shooter is to big u should be around 35 or 37 in the front and the back other wise u r wasting fuel is all....set your shooters tell you get best time then change your carb cam to another setting until it starts to fall away then reset your shooters.........my car with me in it is 2645 and i use a 37 shooter any bigger does nothing for me....weight of your car has alot to do with it as it takes longer to get a bigger car moving hence the smaller shooter will give you the same amount of fuel as a bigger one but over a longer period of time.....same with your carb cams they react with your throttle so the curve of them controls your shooter fuel............that is why they have holes in them to make them more agressive or to slow it down same reason the diffrent cams have longer or smaller rams to control the fuel curve to the shooters

[footbrake]

fisherman is right, 42's are way too big. They are doing nothing. Try 35's front and back

[JEFF69Z28]

HAD 31 IN FRONT AMD 35 IN BACK,WHEN I MASH THE GAS IT WOULD SHUT OFF, KEPT GOING UP IN REAR UNTIL HESITATION STOPPED WHICH WAS A 41 IN THE REAR,35 IN FRONT.LAST SUNDAY IT WENT 11.64 FROM A PREVIOUS BEST OF 11.90.ALSO FOUND THE VAC.LINE TO PCV VALVE HAD A NICE CRACK IN IT SO I REPLACED IT TODAY AND WILL RUN IT FOR THE LAST TIME WITH THIS MOTOR ON SUNDAY.ALSO TOOK ABOUT 120-130 POUNDS OFF THE CAR LAST NIGHT.THIS CARB I THINK NEEDS REBUILT BUT IT WILL PROBALY BE TO SMALL FOR MY NEW SET OF HEADS AND CAM SO IM NOT GOING TO WORRY ABOUT IT ANY MORE.
THANKS FOR ALL THE INPUT....
JEFF

[mopar1968]

I still say you are sucking air in from somewhere, all you are doing is adding fuel to compensate for the air..

[JEFF69Z28]

I SAY THE SAMETING BUT CANT FIND A LEAK.

[fla1976]

I agree with mopar1968. Sounds like a leak. Have you checked the linkage at the butterflys. Sometimes they get worn and start leaking thru the pivot. One way to check is to spray a little WD40 on the pivot while it's running. You can spray around the base also. If it changes the idle it's being drawn thru the pivotor a leak. Or try choking it partially off with your hand, if it picks up rpm , it's getting air from somewhere.

[camarotale]

a 750 holley is not a favorite of mine I changed squitters, cams, jets, you name it. the only thing you can do is send it to a pro, it will work ok if you just drive it but if you want preformance when you floor it , it will hesitate,just to show I know what im talking about, turn your idle screws open to a point where it is gasing big time , like 3 to 4 rounds out and your hesitation will be gone, but you will stink up the garage and polute your oil, but it will show where the problem is and it cant be fixed without a pro getting into that carb, stop killing yourself , I have been there, I bought holley books and talked to every motor head i know and my problem was gone when i sold it and went to a 950. I suggest selling it and buying one from pro systems

[dparker]

:?

[mopar1968]

When i bought my engine from sonny's engines it came with two intakes, mopar m-1 and a indy, i tried both intakes, tuning the engine, the m-1 did not run very well idle was erratic up and down, so i went to the indy, run's perfect, come to find out the m-1 was warped 0.02 at the intake to head runners, no coolant leak but did leak air, sonny's said this was probably caused when they ported and polished runners, could have gotten too hot. just a example of what happened to me hope it help's you out.

[jmlebel]

You want to tune your shooters to do more than just cover the hesitation, your shooters will make all the differance in throttle reponse, your motor can make good power in conjunction with throttle responce if the AFR is kept at the right ratio as you open your throttle plates. If the motor goes to 14:1 or 15:1 AFR as you open the throttle you lkely won't notice a hesitation, as you would when real lean around 17:1 or a back fire around 19:1, but if you keep the AFR in the 12.5:1 ratio as you open the throttle blades the motor will make optimum power that you will feel in instant throttle response and torque. The point is keep tuning for optimum throttle response rather than just covering the hole. you will be very happy you did. Also don't forget the other aspects of the acceleator pump circuit, the cam, pu :cry: mp size, shooter nozzle style.

[cepx111]

Just curious, have you tried a 50cc pump?
On them troublesome 750 dp's I always swap out the smaller 35cc pumps and go with the bigger 50cc pumps - usually 9 times out of 10 them hair pulling WOT hesitations will go away instantly.
You need super crisp off idle throttle response for them killer lights and quick short times, especially if your foot braking.
I'd start with the primary first then go to the back if it stills needs more.
Always worked for me, goodluck Cp