Float level in HUF38 / HIF44
Turbo Mini Forums

I've recently installed a wideband lambda sensor to try and get
the needle sorted in my car. I rebuilt the carb (HIF38) before starting
this process but am having problems getting a solid idle AFR set.
I thought I'd followed the instructions for setting the float height
correctly.

I'm starting to think the float level might be too low, the jet's ~4mm
down from the bridge to get the idle afr roughly right.

With the dashpot/piston assembly removed I turned the engine over to
fill the float bowl, the miniscus of the fuel looked like it was about
another 3mm down the jet.

That's not right is it?

Does anyone have an idea of roughly how far below the bridge
the meniscus should be?

Thanks,

Nial.

Nial.

What cc ?
What cam ?
What rockers ?
NA or turbo ?

If it's a std 1000 on a HIF38, then I'm no good at the jet tube height.

However, for a 1275, I know that for an HIF44, to get a steady AFR within the range 14:1 - 15:1, then the jet height can vary between cars as to be level with the bridge to about 3 mm down the jet holder (which is about where mine is on my turbo van on an HIF44).

The choice of cam is important as it'll dictate how lumpy your idle is. An MG Metro cam can be somewhat lumpy and to ensure a steady AFR (and be successful at passing MoT emissions) it's sometimes worth opening up the valve/rocker clearances a bit to say 0.014 in / 0.017 in ex when cold.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Sounds too rich if the jet is that low.

You will get a very erratic idle whether its at the extremes of too lean (a high AFR) - indicative of a jet that's too high, fuel supply issues (flow or pressure, pump, float or float needle valve), or an air leak in the inlet manifold, vacuum tubing to dizzy etc, or too rich (a low AFR) - indicative of a jet that's too low, choke stuck on or maladjusted or a blocked air filter or air inlet).

Take the plugs out, give em a good clean and reset them then bung em back in. Run the engine up to temp (ideally without any choke if you can so that it doesn't soot the plugs too much) then pop em back out and check the colour - jet black indicates over rich, very light tan is too lean.

You'd do well to check the float needle valve is sealing properly when you're checking the float height (which if correct, a straight edge should just kiss the plastic float when placed from one side of the carb bottom to the other with the carb upside down - check the Haynes manual if in any doubt).

Poor idling could be a myriad of things which will include dizzy timing at idle - worth getting a strobe light on that as well as it only takes a few minutes.

Good luck.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u