9 replies to this topic

[redmini]

:wales: I've consulted the haynes book of nonsense and it says to set the float between 20 - 40 thou, which I have done yet the carb is still over fuelling and choking the engine. The needle valve above the float has been replaced with a ball valve (previous owner I assume) which is free from dirt an in good working order, the fuel pressure is 3 - 3.5 psi at idle too. It must be the float level as the petrol keeps running through the carb when the engine is switched off, does anybody have the correct float settings please?

[Wil_h]

The needle valve should easily be able to stop 3.5psi of fuel pressure.

I've never measured the float bowl setting I just bent it to increace the pressure on the needle valve and stuck the carb back together and tried it.

Obviously you don't want to bend it too far as you will reduce the bowl capacity.

Trial and error is the best way.

Wil

[Dan]

I asume this is a HIF as it's for a turbo.

I have the data for a standard HIF, but not the sealed one.
1.0 +/- 0.5 mm (0.04 +/- 0.02") which would mean 20-60 thou, so you can't be far off. I would check the valve again as the newer designs tend to be a bit rubbish. A lot of tuners will junk the valve even in brand new carbs and fit good used ones.

If the level in the float chamber is low you don't just loose capacity, the level in the jet is too low meaning the the mixture will be a little lean. It would make it hard to profile a needle as the venturi won't perform as designed.

[Wil_h]

It shouldn't make any differance to the mixture, well not on a turbo anyway. because the fuel is pressurised once you are on boost so it forces it's way past the needle valve and will fill the bowl anyway.

It will affect mixture on a NA car though, you're right

Wil

[Dan]

Very true, I had forgotten about the variable pressure regulator. However turbos aren't on boost all the time and at idle is when you would suffer the most from a low fuel level, as the venturi depression is negligable.

[Dan]

Could it not be the pressure regulator causing the trouble for Redmini?

[Wil_h]

Agreed.

But I still bent mine till it worked and it seems fine although probably could be better.

If it aint broken I'm not fixing it.

Wil

[redmini]

:wales: To answer you both it's not the pressure reg as I've got a gauge fitted inline while I'm setting things up, anyway I set the float at 25 thou and it's running. The problem I'm getting now is it's struggling to get revs when I open the throttle, I've varied the c/o's between 0.5 and 3% and it's the same result. When it finally gets up to speed it plooms blue smoke from the exhaust and shoots flames about 3 foot long with a bang on the over-run, the needle in it is an XY57 so I'm presuming that is the problem. I have a standard needle and jet so will try fitting that when I get chance, I think the other needle etc. is for running higher boost? than the standard I'm running until the engine is run in.

[Turbo Phil]

Standard needle is BDD, though if it's putting out blue smoke this is oil ....

Phil.

[redmini]

:wales: I thought that to Phil but I can smell the petrol in the fumes and the oil hasn't dropped at all. I've got a BDD so I'll try it, if it does turn out to be oil I've a standard 1275 in my shed :wink: