correct fuel pressure for 396. bbc 7 1/2 to much?

lsbw17

Daily Driver
Dec 11, 2012
16
0
0
weatherford , tx
Im having a problem with my carb runnin rich ive changed the jets to
76 in front 86 in the rear this is a mighty demon 750 dp. Im runnin 7 1/2 lbs of fuel pressure
It seam to load up an run rich at idle but pulls every where else. I have my primary an
Secondary air bleeds set at 3/4 turn out an transfer slots are barely exposed just a square is showing in the bore . . . I have 10 lbs of vaccum at idle an a 6.5 power valve ..... do I back the fuel pressure of a bit? ? ? Any ones advice would be nice


Thanks larry
 

alex383

Frequent Racer
Aug 16, 2008
369
0
16
douglas az
lsbw17 said:
Im having a problem with my carb runnin rich ive changed the jets to
76 in front 86 in the rear this is a mighty demon 750 dp. Im runnin 7 1/2 lbs of fuel pressure
It seam to load up an run rich at idle but pulls every where else. I have my primary an
Secondary air bleeds set at 3/4 turn out an transfer slots are barely exposed just a square is showing in the bore . . . I have 10 lbs of vaccum at idle an a 6.5 power valve ..... do I back the fuel pressure of a bit? ? ? Any ones advice would be nice


Thanks larry


i use a 9psi behind my 850 proform whit blue holley whit 0 problems ;)
 

lsbw17

Daily Driver
Thread starter
Dec 11, 2012
16
0
0
weatherford , tx
Lol thats about right man . . It runs good at wot but runs rich enough to burn eyes. I dont think it has as much throttle response as it should
 

Ed Cannon

Pro Stocker
Jul 17, 2009
1,682
0
0
Johnson City Tn
Main jets do not effect idle. Check your float levels. Check for raw fuel dripping into the carb while running. Make sure to properly adjust the idle mixture screws. Turn them about 1/4 turn at a time one at a time.
 

10secBu

MalibuRacing Junkie
May 21, 2003
4,284
0
36
Westminster, MD
Fuel pressure will not affect idle mixture IMO.

Sounds like you need to go over the basic setup from square one.

Properly set the throttle blade position so the transfer slots aren't exposed too much. Set primary & secondary blades equally.

Set baseline idle mixture screws at 1 1/2 turns out from lightly seated.

I set idle mixture screws for the highest rpm idle in gear, then back down the throttle blade position to achieve target idle rpm.

Ideally when the carb is correct, the engine should restart (when fully warm) without needing to touch the gas pedal. If you have to pump the pedal a little to get it to start the idle is lean, if you have to hold the pedal open to start it's too rich.

Again, when checking idle quality & rpm, it needs to be done in gear. Make a change to the carb, climb in the car, hold the brake and put it in gear to check how it idles in gear. If it stalls the idle is likely lean.
 

lsbw17

Daily Driver
Thread starter
Dec 11, 2012
16
0
0
weatherford , tx
Thanks guys sorry I just replyed . . . Havent been on in a while . . . I since then got it to idle perfect an throttle response is great . . Went to a 5.5 power valve an made small adjustment s
My secondarys where opening way to fast also . .some body tweaked the arm so the primarys an secondarys where both opeing around 2000 rpm . .thanks guys
 

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