I have a quadrajet on my boat and was told the secondaries were running lean?

Question

does anybody know if i can change the jets to fatten it up?

Answer 1

I have been separating fuel problems with a propane torch. They are handy and can be reloaded in the field. First get the engine to duplicate the problem. Next point the torch (not lighted-right?) at the throat of the carb while under way and give it a brief shot of propane. If the engine loves it -you are to lean- If it stumbles alot- you are to rich. Either way you can get a real idea which direction to go with out pulling spark plugs.

Answer 2

Secondarys have different  rods to match the engine>It running lean as there not opening up> Chock not open adjusted wrong> Something hanging up> Vacuum pod not working> Have to look and see what not working>Many adj on that card>

Answer 3

Is the carb original to the engine? If so you don't need new rods for more fuel. I would be looking for other problems. If no one has been inside of the carb,and the boat falls on its face when four barrels kick in check all fuel filters. Easiest way is to change out carb filter, then run new piece of fuel line to five gallon tank. If ok then start changing other filters; water separator;then tank filter, if problem comes back, go back to five gallon tank,to you got problem nailed down.Good Luck!

Answer 4

Secondaries don't have jets, It's rods and hangers. Real easy to change, one s***w holds the hanger and they lift right up. Hard part would be choosing which rods and/or hanger to install. Secondaries could be lean because of an internal problem. The person that diagnosed the lean condition should be capable of fixing it.

The way those secondaries work is the top butterflies open from the amount airflow, they move the rods up richening the mixture to match the amount they have opened. Like Wereifsnyder is saying, If they were correct already then they are not the problem. If you are in fact taking in more air while they are in use then they just open a little more and raise the rods adding more fuel. Ambient conditions on two different days could change enough to show a 200rpm difference. I'd make sure and make two runs back to back, one with each arrestor to confirm it's the cause. Quadrajets are designed to be generally rich on the secondaries however the primaries are designed to be efficient consiquently on the lean side. My experience is that older carbs often need larger primary jets by one or two sizes, I assume it has to do with the difference in todays fuels. Primaries are however harder to change and have jets and rods. I'd jump up two jet sizes and test drive it again with the same weather conditions, it should respond better at part throttle too if it likes it.

If this carb has many years on it or your engine is modified I'd consider having it overhauled. I'd use a carb shop that specializes in quadrajets and modifing them to match your engine and use. If you check out some GM Camaro or Chevelle performance type bulliten boards, you'll find some carb builders that people are really happy with, I don't recall the name of any of them and you'd probably have to mail it to them.