CC247

My stock jets say 743 on them. What does the 3 mean? If i want to rich it up should I go to 76's. I've got a 4160 and it's pig rich at idle. I went to 72's and it was too lean. So I want to go to 76's and close up the idle screws. Sound good? Also I had a vacuum gauge on it today. at idle I've got 12", when getting on plane it's at 2-3 ", on plane vacuum is around 6" at 3000 rpm. Is this carb too small? It's a 600 on a 460 BBF. It looks as if the power valve would be open at cruise . It's a 6.5

BUIZILLA

the triple digit jet numbers reflect the taper on the threaded end inboard seat area, makes for smoother fuel flow, so they say...

CC247

let me refrase my question. Today under cruise condtions at 3000 rpm, on plane I only have 3" of vacuum. Would this be a ignition problem? I put my timing light on the engine and at 2500-3000 I've only got 20* and it jumps between 0* and 20*
I've got one of those spitfire systems, maybe the module is going south?. While cruiseing it also sounded like the carb backfired and then ran rough until I got it on the trailer. Probably blew the power valve? I've got problems and the old lady ain't happy.

Griff

Jetting has absolutely nothing to do with being rich at idle.

A 600cfm is too small for 460ci. You need more like 750-800 if you are turning 5000rpms.

PatriYacht

Something is wrong with your ignition system if the timing is jumping around like that. While I don't know much about Fords, I think the timing should be about 34 degrees at 3000 rpm's. That's likely why your vaccum is so low. Changing jets doesn't affect idle mixture. It's probably idling with low vacuum and the power valve is open flooding the engine. Initial timing should be around 14 degrees.

CC247

Thanks, I just checked the timing and it's at 8* idle, but jumps all over at 3000rpm. I'm going to look into a new distributor and scrap this spitfire system.