Snakebitekit
The above are my 48 IDA’s this may help. The Key is balance of air flow, and fuel is the last thing you worry about. The first thing is get the engine running. If it does run but not smooth that’s OK. To help keep the engine from running to rich or to lean adjust all your fuel metering screws to 1 turn out this is just to get the engine running we will revisit the fuel at the end.
Tuning the carbs takes about 20 min. So maybe some extra fans will help the rad. with air flow.
You will need an Air Flow Meter and a Temp Sensor Gun.
The layout of the carbs is when I say R.R.(Right Rear) it is from the cockpit view point.
Now disconnect the left bank of carbs from the Right bank, should be a turn buckle bar between them.
Start the engine, should still run unless the bar between them was holding one bank of the carbs open then you must turn the idle screw until the engine will run without help from you.
The Sequence for tuning is as follows R.F. and R.R. must = each other. The reading between the two carbs must match and does not matter what it is on the meter as long as both are the same, this is done by adjusting the screw on the linkage between the two carbs , then adjust L.R. = L.F. Once this is done the engine may be racing or could be stumbling you may want to adjust the idle speed a little, try to get it around 1100 RPM’s
Turn engine off reconnect the Left side carbs to the Right side carbs.
Start engine and adjust using the connecting bar and using the flow meter and adjust the Left and the Right bank of carbs, again the reading just has to be the same. By now you should start to understand what is going on here.
If all the adjustments have held the flow thru all the carbs at this time should be about the same.
Turn off the engine
Now the fuel flow. Because you can’t monitor each output of each cylinder we will use two techniques that will give you the best chance of carbs that will perform well.
Just a quick review, Rich is too much fuel and will run Cold at the exhaust. Lean is not enough fuel and will run HOT at the exhaust.
Each carb has two fuel flow meters, one for each cylinder. The book on this is turning the screw in all the way and back out ¾ of turn this is just a baseline. I know I had you adjust them 1 full turn this was to make sure we did not run too lean.
Once you have done this start the engine and adjust the idle to about 950-1000 rpm’s. At this point using the Temp sensor gun, check the output of each cyl.. Check just past the flange about ½ inch away, do not check it on a curve or bend of the pipe that will read hotter and will give you a bigger delta between the outputs of each cyl. The reading will tell you if the cyl are running the same fuel flow. But we want to know if it rich or lean. The book will tell you to turn the screw in on each cyl until the engine stumbles and back out until it is smooth. You may have to repeat this a few time as the engine starts to run on all cyl’s so lets do that and now check the temps again.
The temps can run from 350 deg (to rich) to 800+ deg (to lean) the number will or should be between 600-700 deg each engine will be a little different.
The exhaust temps when the engine is running will or should be within about +/- 10 deg of each other. This will tell you that all the cyl are running close to each other.
When done take it out for a test drive it should be fine if timing is set right, if you do have a flat spot on hard throttle could be timing or the run jets need to be changed this gets a little more involved. But most of the time it is timing and or the advance springs are wrong.
48 IDA’s will not get you great gas mileage but depending on horsepower can be between 6-14 mpg . My 351w above put out 500HP and got around 7mpg
Good Luck
Joe
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