How fix F/A distribution

pa38112 · #1 03-28-2016, 10:58 AM

I have an O-360-A1 and see about 1.5GPH spread between 1/2 and 3/4 (3/4 run richer). 1/2 are very close, and 3/4 are very close. This is at about 2300rpm. If I try to run WOT it gets much worse and the engine is too rough to run lean.

I attempted to correct this with an airflow straightener on the intake to the carburetor (per another thread). This worked very well at 2200rpm, but made the spread worse at higher rpm's.

I am considering trying to add a cross-flow pipe between the 1&3 and 2&4 intake pipes. Has anyone tried this, or have an opinion? Does anyone have a set of used intake pipes they would like to sell?

lr172 · #2 03-28-2016, 11:25 AM

I have the exact same behavior in my O-320, although the GPH spread comes down some at WOT and my EI upgrade reduced it a bit as well. My answer is to upgrade to Bendix FI. I don't think you'll have much success, but am interested to hear of your results. It would seem that the very small plenum volume in sump is the primary culrprit. If I were experimenting, I would be building a bigger plenum in the sump.

Larry

pa38112 · #3 03-28-2016, 12:59 PM

Quote:

Originally Posted by lr172

If I were experimenting, I would be building a bigger plenum in the sump.

I don't think the size is critical as long as it is as big as the carburetor intake, but I have considered some mixing veins or baffles in the plenum...

Carl Froehlich · #4 03-28-2016, 01:11 PM

Since you are looking at this, I suspect whatever incremental improvements you might achieve will not meet your satisfaction.

The Airflow Performance fuel injection is a bolt on carb replacement for your O-360 engine. I did this on my first RV before Van's was selling the 180hp IO-360 engines. Good decision then - and still is.

Carl