dual quad high rise & holly 4barrels

[dirtydog]

How do I go about adjusting them? Dunno much about holly n not mine. Sbc. Cam lil over 500 lift. Need to get it to idle. Back fires threw the back carb . Got new summit distributor.  Msd ignition.  Would two edelbrock  600cfm b to big. What would u z
Set the timing at? What should the idle rpms b ?  Thanks for any and all input . May have more? To come 

[frdzila]

That is way to much carb for the cam and cubic inches.

[4x4xdodgeman]

are you saying its a tunnel ram set up? or just short dual quad intake?  first off what holleys are on it list numbers,  and 600cfm carbs are not to big for a tunnel ram set up.

[MR NASTY]

They are way to big for that motor.

[MR NASTY]

750 cfm will be more than enough for that motor. Ditch the intake and put a good dual plane intake on it and your gonna be farther ahead.

[dirtydog]

like 425 525 hollys. know about switch intakes dont wanna unless he has to. dual high rise intake tunnel ram

[MR NASTY]

With the minimal specs you gave 500 lift sbc that set up will cost you performance. Your gonna give up all your low end grunt and I'm guessing from the specs you don't have the upstairs. With a 500 lift cam the valves are gonna float long before it gets to where it hits the rpm range of that setup. Might work but it's only gonna run right on the floor not to mention the hassle of properly tuning 2 carbs let alone one. You said it's backfiring so at a minimum you need to tear the one carb down to change the power valve.

[dirtydog]

i prefer edlelbrocks but not mine n different strokes for different folks lol its in a prostreet camero we brought back from jersey shore lol dont think guy new much before he sold it to us lol

[dirtydog]

has a 7000 rpm chip in it when we got it

[Jthomas]

Kill the fuel system (so it won't start), and set the timing 8-10* advance at cranking speed. Turn the fuel back on and Guarantee it will start.

I like to adjust my idle speed to about 700rpm with the truck in gear and foot on the brake.

Adjusting dual carb setups is really simple. They have to be a mirror image, whatever you do to one carb, has to be done to the other. Same jets, same power valves, set the screw on the idle to the same position, set the air bleeds the same.

Turn the air bleeds in all the way, then back them out 1.5-1.25 turns.

Then re Set the float height the same, loosen the jam nut on the float bowl, remove the plug screw on the side of the float bowl. then with the fuel pump turned on, either turn in or back out the needle and seat, just until the fuel level is just about to puke out the plug hole. YOU DO NOT want it FLOWING, you want it really close to coming out. So if you rock the truck, and the fuel dribbles out the plug hole, then it's close enough.


When adjusting idle, your not going to just turn one screw in our out on a carb. If you turn one in 1/16th of a turn, then you do the same to the other.

As you already know, you have way too much carb, but if your not going to change it, that will Atleast get you closer than you are.