Weber Jetting Survey

[*13*]

Originally Posted by Caprimaniac

13; I cannot remember seeing you testing A/F ratio? It's very useful as to get the webers correct. Hesitation at either RPM can be due to too much or too little fuel. It is also possible to trace the problem by reading plugs.

Changing the pump jets (exhaust) to 00 I think is mandatory... See Eljaro's posts on this.

As of yet I have hooked the motor up to an A/F machine. Reading plugs at this point, learning the hard way

[Gaz64]

Reading spark plugs will only give you an average indication of A/F ratio.

Lean at one end and rich at the other (or vice versa) may give a good reading.

You need a fast operating wide band O2 sensor gauge with data logging capability to pick accelerator pump accuracy (rich/lean), idle circuit/progression/main circuit overlaps etc.

[Snakebit]

My plugs looked good, light tan. But I was too lean above 3000 rpm AFR was 17. Went up 2 jet sizes to bring it down to 12.5. Reading plugs will get you close, but a dyno lets you zero in.

Take your distributor to some one with a Sun distributor machine to recurve your distributor. You want a total of 38* all in by 3000 rpm. That was a surprize too. Jim Inglese said to run 20* initial advance and 18* in the distributor for a total of 38*. Also keep the fuel pressure at 2.5 psi

[dlampe]

I disagree with the 00 pump jet. Engines are different and have different fuel requirements. Mine bogs with the 00 and with the .55 but runs great with a .40. I have tested about every possible combination of jets, e-tubes and exhaust jets and that is what is making my engine happy.

[Snakebit]

I started with 50's, dropped to 35's and finaly with 00. You are correct that each engine is different with cam, heads and choke sizes.