Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

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1mainiac:
I have a 26ft boat with this carb recently replaced the 350 with a 383 long block boat performance has gotten worse. Mid range has improved however top end is lower. Idle is way too lean so it stalls on every shift out of gear I have to send the rebuilt carb back as it is messed up and they will replace it however what jets should be in this setup. I am going to rebuild my stock carb over the winter since I have a second boat with the same engine setup which I will be getting ready for next season. The 383 long block was installed by a  shop and nearly everything was replaced during the upgrade. Which included new fuel pump new Distributer new water pump and belts it has no vacuum leaks. The issue is it runs much worse with the rebuilt carb than with the 26 year old stock carb since I will have 2 carbs I have some room to play around and dial it in. However I want to be fishing not working on the boat. The  rebuilt carb has damaged idle mix screws and they are replacing  the carb what bothers me most is I should get more top end out of the new engine, it has 30 hours break in on it. the motor will not make over 4000 rpm I swaped  props from a 17 to a 15 and all I got was lower speed it still would not go over 4000 rpm. My thought is the carb does not have jets enough to provide the CFM needed The old 350 would run about 4300 with this carb which if my math is correct is about 440 cfm the 383 runs 4000 which is  436cfm by my math. To get where I want I need 650 cfm running correctly what should I use for jets and adjustments?

StillLearning:
Welcome to the blog!
  With all the new stuff and changes to your engine take some time and make sure some of your basic settings are correct. A lot of what seem to carb problems can be ignition timing, fuel pressure or some other thing that was overlooked.
 That said, most commercially available "rebuilt" carbs are not all that good. Each one is built for several different applications and usually are marginal for said applications. You would be much better off taking the original unit and building it with Cliff's parts. Most rebuilts use some pretty cheap innards.  With Cliff's parts you get the right parts and the newer alcohol containing fuel won't be a problem. Consult with Cliff to find out what changes you need to make to your Q-jet. He also has a rebuilding service if you don't want to try it. Believe me it will save you time and hassle in the long run. Happy fishing!

1mainiac:
I have no problem with rebuilding my own carb what I don't have is experience with Quadrajets frankly I am one of the guys that always tossed them out and installed a Holley. Not that I thought they were junk but I grew up with Holley carbs and could tune them in my sleep years ago. So what I need is a base line to work with. I would prefer fat and happy til I get some more hours on the engine. Not really looking for huge performance but I expect it to make decent power and be able to hit upper RPM when needed. On paper this setup should run 5200 to 5500 pretty easy which a friend of mines similar setup does with a stock 350. I have a few more weeks to sort this out before I put it to bed for winter. If it does not start to behave soon it will have a TBI on it next spring.

77cruiser:
Do you have Cliff's book? It has some baseline combos in it.

Cliff Ruggles:
The problem is going to be with the "rebuilt" carburetor.  I do this for a living and will NOT work on them, and don't even want one sent to my shop for any reason.  I'd send it back and completely/correctly rebuild the original carburetor with one of our kits.  I'm betting at this point your carburetor issues will disappear.....Cliff

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