i need help on tunning my holly 600 cfm carburetors i have two because i am running a tunnel ram. we need help on how to tune the dual carbs so we can get the car running right.
i know it won't run perfect but we know it will run to where we can drive it we have had it there before. i just need help on how to tune dual carbs
You need to get a carburetor synchronizer and an adapter for your carbs to use it. You start by getting it to run at an idle. Close the throttles on both secondaries and the rear primary bores. screw the rear idle adjustment needles all the way lean (most are in) to shut off fuel to the rear idle circuit. Then adjust the front throttle on the front carb to about 1 -1 1/2 turns in from full closed. Adjust the idle mixture needles on the front primaries to gently closed and back them out 2 turns (+/- 1/2 turn). Set your timing and then idle the car - fine tune the idle speed and mixture using a tachometer. (you can use a vacuum gauge but I prefer the tach) get the highest idle with the mixture screws and then set it at the right speed with the throttle stop screw - readjust the mixture for the highest rpm and adjust speed with the throttle stop screw. Keep doing that until it is right on then turn the idle mixture screw out (richer) 1/4 turn. From this point on you need the synchronizer because as you add the back carb you have to subtract the front one until they flow the same amount of air at the right rpm with the best mixture .... It is a long laborious job and the adjustments need to be locked in using "After-torque" or you will be doing it again in a month. Good luck! I used to do this often when guys had multiple carbs but since carbs are now made to cover any application with a single four barrel there is no reason to run more than a single carb on the street.
There are no rear idle circuits on Holley 600's. And you need no syncronizer. Both carbs need to be kitted identical to start with. Then you're going to have to figure what powervavles to run. That's going to be decided by reading the plugs or using an exhaust analizer to see where the mixture is in normal driving. You will also need to connect the vacuum pods for the secondaries together as well as use the same sec springs in both. That will insure their opening equaly. As for the primarys, the throttle linkage needs to be adjusted to where both carbs are opened fully at WOT. You can set one as the idle carb and close the other, if the engine will idle on one carb. You may also fine tune it by playing with whichever carb is giving the leanest plug readings by way of jetting and throttle linkage settings. There's proably more, but this is a start, it's been awile since I ran a 2x4 setup and then it was on a lowriser 427, not a Boss 302 with a tunnel ram. My advice to you is sell the tunnel ram setup and use the proceeds to buy a new Edelbrock RPM airgap intake and a single 4 carb. You will end up with more hair on your head and lower blood pressure. That's all unless you can find someone locally who knows how to tune it for you.
I would think with two vac secondary carbs if you put heavy springs in the secondarys or just disconnected them all together it would run like a 600 with four corner idle circuits, but i may be wrong. But boteh carbs do need to be the same calibration all together. And when you tune one be sure the other is exactly tuned the same. Just my thoughts, i never fooled with this but thats what i would do.
Ummm.....after a few dyno sessions under my belt at my old friends Red machine shop I gotta disagree both carbs are tuned exactly the same.... In fact if you tune each cylinder for max perfomance jetting will be different from runner to the next...
