4150 likes to die on hard acceleration

1606 Views 22 Replies 10 Participants Last post by 406monte, Jul 7, 2009

406monte

Discussion Starter · Jul 3, 2009

I need some help on my 750 Dp it is a 4150 and i just rebuilt the carb and installed it and it runs really good till i get at around 2500 rpm and then it starts to surge and stutter. I don't know why this is happening i have checked everything i know to check. I starts right up and idles fine. I have checked the floats and they are good and the fule preassure is set at 6 lbs. I have 30cc pumps and 6.5 power valve and 67 primary and 72 sec jets in it. I have 31 primary and 37 sec downleg squirters. I put them in there from the 31's that were in there both front and back. Also, if i am taking off fron a dead stop and hammer it down it takes off really hard then it seems to stumble and act like it is trying to float out on me and i have to peddle it to keep it from dying on me. It has done this to me once yesterday and it tried to die on me once today as well but i kept it going. Any help would be apprecitated i want to take this to the local midnight madness and see if it picked anything up from the old 750 vac sec Holley that i had on it.

Eric

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Drag Chevette

· #8 · Jul 4, 2009

The main jet controls most cruise & W.O.T. fuel metering.

The main jet under cruise conditions supplies the fuel and this circuit is easiest to tune.

If @ steady speeds (2200-4000 rpm / return road rpm) the engine surges it is too lean.

looking for economy?......You can usually lean the main jets down till you get this surge at 2200 rpm & then richen up the mains by 2 jets #’s to be safe.

its a 750...try 75pmj and 83smj,....with a 5.5pv

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Drag Chevette

· #9 · Jul 4, 2009

I went up to 72 prim and have 73 sec jets in it. I checked the power valve and it is good.

DUDE, when you run a primary power valve and the secondary is blocked....you need to increase the secondary jet 8-10 sizes.

the flow from your power valve channels along with the jet flow need to be close to the jetting in the rear if the rear is plugged.

right now with a 72 prim and 73 sec jets in it and a power valve your about 8 sizes lean on the secoondary........

try jetting it 75-83 and report back.

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