I've now got my car (RP saloon) running with the SU carb and the fuel staying mostly on the inside of it, but I need some advice on tuning it.
It's a rebuilt engine. Standard valves and cam with the combined inlet / exhaust manifold. Standard exhaust.
It has a high compression head which was skimmed a fair bit to flatten it.
I'm using a DK4A distributor but not sure what advance profile it has (LC or HC).
Timing is set slightly advanced from TDC at idle. Should this be dead on TDC?
Carb is an SU H1 (1 1/8") with no spring and the brass weighted piston.
The carb was bartered from another owner. It's since had a complete new jet bearing assembly (the superdry version) as well as a service kit with new jet.
It currently has a VS needle which looks from the charts to be too rich for a fairly standard engine.
Jet has been centred and the piston rised and falls smoothly by hand and drops with a click.
It doesn't fully open when you rev it with no load, but I've read that's not unusual on a standard engine.
At present, the car starts and runs pretty well but all indications are that it's running too rich, both at idle and on the move. I have a lambda boss welded into the exhaust with an AFR meter in a mobile box connected to it.
At present, I'm struggling to get the mixture weak enough at idle and still have it run smoothly. Tightening the mixture nut (to make it leaner) makes the idle miss. A smooth idle that sees the highest tickover shows about 10.3 on the AFR meter (too rich). When running the mixture enriches further but that's possibly to be expected with that jet.
The above is born out by sooty plugs.
As I understand it, the selection of jet shouldn't make that much difference at idle unless this one is worn??
Any advice on where to start is appreciated.
It's a rebuilt engine. Standard valves and cam with the combined inlet / exhaust manifold. Standard exhaust.
It has a high compression head which was skimmed a fair bit to flatten it.
I'm using a DK4A distributor but not sure what advance profile it has (LC or HC).
Timing is set slightly advanced from TDC at idle. Should this be dead on TDC?
Carb is an SU H1 (1 1/8") with no spring and the brass weighted piston.
The carb was bartered from another owner. It's since had a complete new jet bearing assembly (the superdry version) as well as a service kit with new jet.
It currently has a VS needle which looks from the charts to be too rich for a fairly standard engine.
Jet has been centred and the piston rised and falls smoothly by hand and drops with a click.
It doesn't fully open when you rev it with no load, but I've read that's not unusual on a standard engine.
At present, the car starts and runs pretty well but all indications are that it's running too rich, both at idle and on the move. I have a lambda boss welded into the exhaust with an AFR meter in a mobile box connected to it.
At present, I'm struggling to get the mixture weak enough at idle and still have it run smoothly. Tightening the mixture nut (to make it leaner) makes the idle miss. A smooth idle that sees the highest tickover shows about 10.3 on the AFR meter (too rich). When running the mixture enriches further but that's possibly to be expected with that jet.
The above is born out by sooty plugs.
As I understand it, the selection of jet shouldn't make that much difference at idle unless this one is worn??
Any advice on where to start is appreciated.