The Stovebolt Site Forums The Shop Area Engine Shop dual Carter W1 issues....

Okay, I have just finished a top-end rebuild of my 58' 235. (Pretty much had the head gone through and redone) I have got everything hooked up and running. Today I set out to get my engine dialed in with the new Carter's and the rear carb is not flowing any air, almost none at all. I can have the engine running, throttle screws all the way out, and the front carb is flowing alot more than the rear. Noticible with just putting your hand over the air horn.

The two carbs are 41'-48' Carter W1's. The only difference between the two when hooked up it that the vacuum plug on the rear carb is blocked with a pipe plug and the front one is hooked to the distributor( not while I was tuning though, had it pluged with a piece of rubber hose and a bolt) Which that may be my problem....vacuum leak at the vacuum port. I will go investigate that possibility, but if anyone sees this post and thinks of something different, please let me know! Thanks!!!

Well, it wasn't a vacuum issue.....

Carb balancing can be a very fickle issue! Start by being absolutely sure, both throttle plates are adjusted identical....A feeler gauge works well.
Be sure both idle mixture screws are both turned out the same amount also, say 1 1/2 turns. Try not to let idle speed get above 600 rpm, if it does, use idle speed adjustment too get it around 450. I have found using my old motorcyle carb balancing/ vacumn gauge works great, but a standard vacumn gauge and tachometer does the job also. Patience and many, many adjustments may be required......good luck !

I appreciate the response Helilog, but I was doing those exact things to adjust them. I had to crack open the rear carb throttle abit to even come close to the same amount of air flow as the front. It has me quite perplexed as my other dual setups haven't had any issues like this. They were just bigger carbs, that's why I'm switching.

I do all my adjusting with the linkage unhooked. I start with with the throttle screws backed out so each throttle blade is 100% closed. Then, using either a dial indicator or feeler gauge, I open each to the same spot. I set them where it should start and run, at this point I am looking for it run, not so much a set rpm. The idle screws are set identical as well. Once started, I can then adjust for idle speed after it warms up. You need to be sure to turn each adjustment of each carb the same amount, its a lot of jumping back and forth. I have used the air flow gauge which helps (http://www.speedwaymotors.com/Edelbrock-Uni-Syn-Carb-Synchronizing-Tool,267.html ). I also use a air to fuel ratio gauge stuck in the tail pipe, which really helps when setting the mixture screws, with two carbs, a little goes a long way.

Once they are set and the idle is correct, I then set up the linkage being sure not to change the throttle positions.

Joe