kksimpkins

Hi Guys,

I had to replace my 2 bbl Motorcraft carb. Since it is almost impossible to find a new replacement, I went with a new Holley 2300 350CFM 2 bbl. I'm having a really hard time tuning it up. I can't get it to idle below 1100 RPM, and if you try to drive the car, the engine dies when you hit the brakes going forward (no problem backing up). Can anyone direct me to a proper set of tuning instructions for this particular carburetor? Thanks!

Gun Jam

other than physical placement of things like jets and idle screws these carbs all function about the same whats true for one should be true for another to some degree.

Now if you cant get it to do something basic like idle at 800 rpm...and its a new carb well maybe its not a carb issue directly.

you must check for vac leaks at this point even if that carb is horribly setup it should still idle if you run the idle mix screws out far enough.

The holly 2300 looks like its simply half of my QFT HR600 which is built off the holly 4150.

I suspect I know the carb you have very well..im just use to it having both halves....im many ways the 2300 should be much simpler to tune.

Im going off of this link https://www.summitracing.com/parts/hly-0-7448/overview/

Lets go through some steps to help you get your carb to idle

1) with it set up like it is now...take some carb cleaner with it running at the lowest possible RPM (sounds like 1100) Spray the cleaner all the way around the base of the carb does the RPM drop significantly at anyone location? that would indicate a vac leak at that point (dont spray it too heavily or it can give false positive if vapor gets sucked in through the carb intake....You might seem some decrease around the throttle shaft as well.)

2) The idle mix screws should be located on the metering block on both sides (the metering block fits between the carb body and the float bowl) the Screws are silver color with a flat head slot and small.

3)Turn both idle mix screws in until they stop then back them out 3/4 of a turn

4) is idle rpm higher or lower?

5) turn both screws (either in or out) in equal amounts until you have the highest idle rpm

6) but our rpm is currently out of tolerance so if an adjustment makes rpm higher then reduce RPM using the curb idle adjust screw (on the throttle linkage lever) see if you can reduce RPM to like 850...Then again re do step 5 until you get max rpm then use curb idle screw to again get back to 850rpm

This should set your idle circuit.

so before you do this

1) check for vac leaks
2) you should verify timing as well you should have 10deg advance at idle rpm.

-Gun

kksimpkins

I dipped the metering block in Berryman carb cleaner for 40 minutes. Then I removed it and sprayed down with carb/throttle body cleaner. I blew out the passages with compressed air. While blowing out the main passage on the driver's side of the metering block, a clump of gunk and carb cleaner popped out. I re-assembled the carburetor and installed it on the car. Once gas was pumped back into the float bowl, the car started and has been idling normally. I adjusted the idle screws with no issue.