Quickfuel Marine 850 Carb
 

Hello,
I know there are many variables regarding the carb setup, I have a 540 with flat top pistons 305 AFR heads nice setup but need a little help with the carb. I have seen some posts claiming they did nothing to the carb others say its just to lean at wide open throttle. Should I leave the setup or change it prior to running it. Any suggestions are welcomed.

AFR Gauges

I run some Quick fuel 850's with a blow through carb set up and I really did not how rich they were running until I put the AFR gauges on it

Install afr gauges, takes out all the guess work, might make difference between making ashtrays or wasting fual.

Don't make the mistake I made. I rebuilt one of my motors and dynod it with the original carbs that came on it and then I dynod it with a holley xp 950 I had bought earlier in the year (brand new). The motor picked up 20 hp so I ordered a 2nd holley xp 950. I put the 950 I dynod on the motor in the boat and put the new 950 on the motor I just rebuilt. It ran fine and seemed normal until I did a full throttle run and the end of the season and I burnt a piston. When I rebuilt the motor (the 2nd time) and we dynod it that new carb was extremely low on fuel. We had to do a lot of work to get the AFR right on the dyno. I guess my point is that 2 of the same carbs can be completely different so either dyno it or get some AFR guages.

I will say this in regards to every QF carb I have run on cars, every single one was pig rich at idle. some so bad you could not be near them. all needed lots of air bleed and idle jet changes to clean them up to run decent.

Mine were definitely on the rich side , I went through a lot of spark plugs before I got the AFR numbers under load where I wanted them .

With the current tech as well as carb tech, no excuses to not run an AFR. Pretty cheap access to real data that will determine the health of the engine.

Once you install O2 sensors to tune you'll never go back to guessing, best thing I've ever done as far as tuning in water.