HIF6 Float question

sdibbers

sdibbers

Well-Known Member
Hi All,

I'm still getting fuel out of the vent on the front HIF6 carb on my 2000TC. I have rebuilt both carbs with viton rubber seals and float valves. However I still have the older style floats with the flimsy '+' cross section arm. I have ordered new replacement floats with the later 'H' cross section arms.

I wanted to check if anybody has had issues with the old style floats causing problems. I have a working hypothosis and wondered if it made sense to you?

The way it normally works is I set the carbs up, the car runs great for about 20 minutes. I'll go for a test drive after tuning. By the time I get back (around 5 miles) There is fuel coming out of the front carb vent. I'll pull the carb, check the float and it will have risen about 3mm, I've also noticed a weird wear pattern on the brass adjustable tab suggesting it's pushing the valve sideways as well as up. Does this sound like a good line of thought?

Has anybody else had issues with the old style floats?

Thanks in advance!

Steven
 
I found threatening them with being thrown across the car park and replaced with a decent carb stopped them misbehaving. my carbs have been on and off more times than a whores knickers in the last 6months.

I also found that it was near impossible to set the float height I spent 30 mins doing it trying to get it bang on 1mm and still ended up with them being wrong. Arthur on here suggested tipping them on their side and doing it I found this a lot easier as I wasn't fighting for access with the straight edge.
coop
 
Yeah, I saw your posts on FB Coop. I think you may have the same issue as me. You were in fact setting the floats to the correct height but the older floats would bend and warp with heat and load from the petrol below them.

I found this article which mentioned the old floats specifically:

"HIF floats that were originally installed are pure junk. The floats were later redesigned with a more resilient nylon material. If you have the early hard plastic floats replace them immediately. Chances are they have already failed."

Full article is here:

http://www.ebay.com/gds/Part-Three-SU-C ... 149/g.html

Well, I should get the new floats tomorrow. The ones in there are beyond flimsy. When I sent a photo to Joe Curto his response was "Hell, I didn't think anybody still had them fitted!" So it looks like most have already been replaced.
 
Well, I fitted the floats. Now both carbs flood. I've tested the fuel pump pressure and it's about 2psi, well within spec. I did find a restricter in one of the unions for the return line. I ended up reaming it out from about 1.5mm to 3.2mm and things are a little better. However, I can't get the mixture right still and I think I still have a float problem causing a variable fuel level.

The only other thing is maybe there's an issue with the fuel pump. I know NADA 2000TC was fitted with a higher performance pump and I used a standard UK spec mechanical fuel pump.

At this point I'm considering switching back to the HS8's. The frustrating thing is that she ran great for a good week before these problems arose.

Does anybody else have any ideas? Floats, float valves and all seals are brand new and the latest iteration of parts.
 
It doesn't sound right, even if you may think that everything within the carbs is right.
I would suggest to bench test the carbs with a spare electric fuel pump with output pressure at least equal with the Rover pump.
It would be much more easier to rectify the fault with the carbs out of the car.
 
Demitrius, the problem seems to happen only when the engine is hot. Not sure if the bench test setup would help. I have manually pumped the mechanical pump while attached and all seems fine. With a fuel pressure gauge attached I'm reading around 2psi, so well below the problem threshold.

Here's the fuel line setup. If that helps at all. Remember that NADA models had a fuel return line to the tank that I had to accommodate. Not sure that the other markets had to have those?
 

Attachments

  • Fuel-lines.JPG
    Fuel-lines.JPG
    76.5 KB · Views: 370
So if heat is an issue what in the carbs gets sticky at high temps I guess is the question.... Are the insides of the carbs gummy or are they spotless?
 
The carbs are spotless. I cleaned them thoroughly before fitting and the fuel going in is clean and debris free.
 
I do wonder if it's a tolerance thing with the needle and seat, but tolerances seem nice and generous TBH
 
2psi is nothing, I know for a fact my SU's in my turbocharged installation were running with 15psi fuel pressure into the float chambers without any issues.

First thought is are you sure the float height is correct? I've personally over the years found trial and error works in getting a reliable seal and float height. Maybe setting them a little lower than the book and a test drive is the answer?
 
Hey Simon, I've set them religiously at 1mm. Maybe I should bring them down to flush and see what I get?
 
sdibbers said:
Hey Simon, I've set them religiously at 1mm. Maybe I should bring them down to flush and see what I get?
Click to expand...


I have always set them so that with the carb inverted a straight edge across the body just touches the lowest part of the float. I've never left 1mm clearance.
 
Just popped the bottom cover off the SU's I just removed, can't remember what the books say but the lowest part sits 5mm away from the body



Float looks like this
 

Attachments

  • 100_9481.JPG
    100_9481.JPG
    67.9 KB · Views: 362
  • 100_9488.JPG
    100_9488.JPG
    89.4 KB · Views: 362
Thanks Simon. Looks like the float is sitting about 2mm lower than the book level. Which maybe a good thing. You have the newer float too, same as I have fitted.
 
Worth a go at least, I do think I had issues with floats before I did my own thing, really can't remember now?
 
+ 1 for lowering the fuel level a little.
Also, i am curious how have you plumbed that return line?
As far as i know, the 2200 carbs i have fitted in my car have no provision for fuel return lines to the tank.
Are the carbs you are using P6 carbs, or are they from something else? Perhaps your extra plumbing is upseting something.
 
They are 2200tc carbs from a Dutch car. Apparently only us cars had the return line. Seeing as it tees off before the carbs it could only make the pressure lower. Especially as I've eliminated the restricter.

I'll certainly try the lower level tomorrow.
 
file.php


Looking at the above, I would lay the straight edge on the carb body on the near and far side in the above pic, so that it laid on the very lowest point in the dip of the float, touching, but not moving, the float itself. The straight edge would lie parallel to the fuel pickup on the bottom of the jet.
 
I measure mine using a straight edge across the bottom of the body and measure the gap between the bottom of the curved edge of the float and the straight edge. As per SU's instructions. I think Simon did it that way as it shows the depth better in a photograph.
 
You must log in or register to reply here.
Back
Top