I have done many months of testing trying to find the right combination of main jets, accerator nozzles, pump cams & power valves on these two carbs. My tests are for the best street drivability, miliage & performance.
The next level is the dyno & the drag strip.
With my engine combination these are the results.
The 4412-500 carb was a hassle, I downsized the accerator pump to the 30 cc capacity, used a modified blue cam with a drilled out accerator discharge nozzle to .0295 with a 2 stage power valve with 71 main jet size.
The results were not what I wanted.
At various ambient temperatures I encountered flat spots.
The final choice was go back to the stock 50cc pump, use the stock brown accerator pump cam, 7.5 power valve to the stock .028 accerator discharge nozzle, with a 71 main jet. The fuel miliage went down slightly, but that was expected to cover up the lean holes in the mixture.
Over all driveability is great with no flat spots & fantastic throttle response.
Your application may require a larger jet size if you have an aussie or argie head with more breathing ability.
Next the 7448-350 carb. That was easy, I used a 59 main jet, 8.5 power valve, .031 accerator discharge nozzle with an orange cam in the #2 position.
Next is a dyno test & or drag strip times to see which is top dog.
Just from the seat of the pants the 500 is much more responsive to the throttle, than the 350 carb but that would be expected, because you are exposing much more air flow at a smaller throttle opening.
The main jet size will vary with your perticuliar combination & use, but this will give you a basic idea where to start.
One thing I found out if you have any camshaft in your engine above stock make sure you run full manifold vacuum to the vacuum advance can to give you a much improved idle, part throttle response & fuel miliage. Only use ported vacuum if you have a stock engine. but you can experment.
Last but not least make sure you have at least 6-8# of fuel pressure with the holley 2300 carburetors & have the float setting correct.
Good luck on your application. William
One area I left out is the automatic choke pulloff adjustment for all 2300 series & including the holley 4 barrel series.
This is from an old post of mine, but I found many users of these carburetors are not even aware that holley has this adjustment feature.
Just a bit of technical advice for you owners of engines with the holley 2300 2bbl or any holley 4bbl with the automatic choke option with this adjustment feature.
The adjustment is for the choke pull off. Many of you possibly have no idea what i'm talking about. When you adjust the choke housing for the proper tension, there is another adjustment many owners are not even aware it exists,
The adjustment is after you start a cold engine the choke blade has to be cracked the correct amount. If the setting is too rich blubbering & black smoke will follow after a cold start, then go away after several seconds or minuites after starting-the other extreme is too much choke pulloff or choke blade opening after startup causing a lean stall. Remember i'm assuming your fast idle cam setting is correctly set.
This setting is on the choke casting. If you are too rich back out the small screw adjustment till the choke blade opens the proper amount to prevent the rich blubbering after cold start-up. If you have a lean stall after start-up you can turn the adjustment in clockwise to slightly close the choke blade for proper richness.
IF YOU MAKE THIS ADJUSTMENT FIRSTS CLOSE THE CHOKE BLADE MANUALLY THEN TURN THE SCREW IN OTHERWISE DAMAGE TO THE CHOKE PISTON IN THE HOUSING CAN BE PREVENTED.
Take a look at the photos & the adjustment screw will be obivious.
Hope this helps many of you holley owners. William
Hope this helps for fine tuning. William
The next level is the dyno & the drag strip.
With my engine combination these are the results.
The 4412-500 carb was a hassle, I downsized the accerator pump to the 30 cc capacity, used a modified blue cam with a drilled out accerator discharge nozzle to .0295 with a 2 stage power valve with 71 main jet size.
The results were not what I wanted.
At various ambient temperatures I encountered flat spots.
The final choice was go back to the stock 50cc pump, use the stock brown accerator pump cam, 7.5 power valve to the stock .028 accerator discharge nozzle, with a 71 main jet. The fuel miliage went down slightly, but that was expected to cover up the lean holes in the mixture.
Over all driveability is great with no flat spots & fantastic throttle response.
Your application may require a larger jet size if you have an aussie or argie head with more breathing ability.
Next the 7448-350 carb. That was easy, I used a 59 main jet, 8.5 power valve, .031 accerator discharge nozzle with an orange cam in the #2 position.
Next is a dyno test & or drag strip times to see which is top dog.
Just from the seat of the pants the 500 is much more responsive to the throttle, than the 350 carb but that would be expected, because you are exposing much more air flow at a smaller throttle opening.
The main jet size will vary with your perticuliar combination & use, but this will give you a basic idea where to start.
One thing I found out if you have any camshaft in your engine above stock make sure you run full manifold vacuum to the vacuum advance can to give you a much improved idle, part throttle response & fuel miliage. Only use ported vacuum if you have a stock engine. but you can experment.
Last but not least make sure you have at least 6-8# of fuel pressure with the holley 2300 carburetors & have the float setting correct.
Good luck on your application. William
One area I left out is the automatic choke pulloff adjustment for all 2300 series & including the holley 4 barrel series.
This is from an old post of mine, but I found many users of these carburetors are not even aware that holley has this adjustment feature.
Just a bit of technical advice for you owners of engines with the holley 2300 2bbl or any holley 4bbl with the automatic choke option with this adjustment feature.
The adjustment is for the choke pull off. Many of you possibly have no idea what i'm talking about. When you adjust the choke housing for the proper tension, there is another adjustment many owners are not even aware it exists,
The adjustment is after you start a cold engine the choke blade has to be cracked the correct amount. If the setting is too rich blubbering & black smoke will follow after a cold start, then go away after several seconds or minuites after starting-the other extreme is too much choke pulloff or choke blade opening after startup causing a lean stall. Remember i'm assuming your fast idle cam setting is correctly set.
This setting is on the choke casting. If you are too rich back out the small screw adjustment till the choke blade opens the proper amount to prevent the rich blubbering after cold start-up. If you have a lean stall after start-up you can turn the adjustment in clockwise to slightly close the choke blade for proper richness.
IF YOU MAKE THIS ADJUSTMENT FIRSTS CLOSE THE CHOKE BLADE MANUALLY THEN TURN THE SCREW IN OTHERWISE DAMAGE TO THE CHOKE PISTON IN THE HOUSING CAN BE PREVENTED.
Take a look at the photos & the adjustment screw will be obivious.
Hope this helps many of you holley owners. William
