su sloper problems

Ian Jones · Posted: Tue Sep 29, 2009 6:57 am Post subject: su sloper problems

my su slopers have a 1mm hole drilled in the body of the carb in different places on each carb.The rear carb the hole is 1 inch from the manifold in the 4 o'clock position and the front carb it is about 2 inches from the manifold in the 4 o'clock position and quite near to the jet.My friends su's dont have these holes so i think they may have been drilled after manufacture but for what purpose?Fuel leaks out of the hole in the front carb[just a few drops] when the engine is stopped.What is the solution?
Also when rebuilding the carb is it best to soak the cork in oil or petrol before fitting?

Chris Card · Guest

Slopers have a small drain hole in the base of the body so that excess petrol can drain away. These holes sometimes get blocked with dirt and should be cleaned out.

I normally fit the corks etc dry with no problem - others may do it differently.

Chris

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

I know this is an old thread but my question might be related

My front carb (sloper) on my 4.5 constantly leaks at the gasket (carb to manifold) when the car is shut off. I'll replace that gasket once I find the problem as I don't want to simply fill the manifold with raw gas.

1.) Where would I find these drain holes?
2.) Surely the float should stop flow into the carb anyway as long as its not set too high? I checked the float needle and seat and both look good, no ridge or scoring.

The car runs pretty rich all the time, but this problem may be the cause of that - so need to fix this first.

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

A bit of fiddling around determined:

1.) Not leaking past the floats - the fuel stays just in the jets
2.) Found the drain holes - they are patent
3.) Continues to leak at the gasket/manifold junction

There is a brass pipe that runs from the bottom of the carb to the manifold junction. What is this pipe for? It seems to connect the fuel to the manifold area. What does it do? And how is flow controlled? Is it the feed to the slow running jet?

Thanks

These are G5
Slopers

Chris Card · Guest

I believe it o be a slow running jet and there is a "screw down" adjuster close to the manifold - just visible in your photo.
My understanding is that it is of no actual value and the adjusting screw should be screwed down to the stop.
If it is open, this might be where your fuel leakage is coming from, as the pipe originates from below the top of the jet.

Chris

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

Chris

That was my thought too. I'll try that and see what happens.

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

No, that made no difference. I screwed it all the way in. Still leaking fluid at the gasket junction. Perhaps it is actually the gasket - if there's a break around that hole it would leak. OK, tomorrow it comes off and I'll make a new one.

Chris Card · Guest

Let us all know what you find.

Chris

Chris Card · Guest

Dan - are you running on an autovac and, if so, is there any possibity that the valves are sticking and allowing it to overfill? This would allow fuel to be sucked back into the manifold.

Chris

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

Chris - I am on Autovac but it works properly. There's nothing to suggest raw fuel int he intake manifold.

I removed the offending carb today. The line that I pointed to in my picture above is a solid brass rod. There are two apertures near the top that communicate with each other, and with the float bowl. One of them lines up with the slow running feed hole in the manifold - but the gasket had blocked both those holes, so they are not in use anyway. All this forced me to conclude that the leak had to be through the jet, then via the drain hole to the outside and track down to the bottom of the junction with the manifold. So I made a new gasket, put it all back together and then reset the float needle a tad longer by unsoldering it. That did the trick - no further leak.

I'm now addressing the same issue on the other carb. Int did not leak before, but after fixing the front one it started leaking. It was likely just barely ok, and with the now fixed front carb there was no path of low resistance to the fuel pressure from the Autovac, so it manifested through the back carb. In the process of fixing that one now.

I do wonder if ethanol laced petrol has resulted in the need for a slightly different float setting?

Robert Craven · Posted: Thu Jul 27, 2017 9:19 am Post subject:

Dan, having adjusted the needle to stop the drip have you checked that that enough fuel is now coming through at full throttle? The adjustment can be quite sensitive. My 3 Litre once suffered from lack of power and misfiring which only became apparent at 60 mph and it turned out that not enough fuel was coming through at full throttle and high revs because the needle couldn't rise enough to allow sufficient fuel flow under such conditions. A slight adjustment cured it, though the fault took a long time to identify.

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

Robert - thank you, I have not driven the car yet as I have to resolve the rear carb first. I think I'll be fine though - with the jet fully retracted I can see fuel in the jet and when I pull up on the float needle, to has plenty of travel and causes quite a forceful ejection of petrol from the jet.

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

Robert - I adjusted both carb float needles to prevent overflow. Drove the car today and it feels supercharged. No problems at 85mph, and much more responsive acceleration. I put an AF meter on it and its still a bit rich, but I'm almost tempted to leave it as its driving so well.

Robert Craven · Posted: Sat Jul 29, 2017 10:01 pm Post subject:

Good. Well done.

Robert Clifford-Wing · Posted: Thu Aug 17, 2017 12:54 pm Post subject:

On occasions I find fuel marks on the floor of where our 3 ltr is stored. I always turn the fuel tap off when leaving the car in its garage.

With the engine not running but Autovac left with its inline fuel tap open, close inspections finds the fuel level easily visible at the bottom of the body of the Slopers where the pistons/needles are located. In fact it seems to surround the base of the pistons. Is this too high a fuel level and, if so, what would be a reasonable adjustment to make to the float level as a start, in an effort to reduce the fuel level?

Chris Card · Guest

Robert Clifford-Wing · Posted: Fri Aug 18, 2017 6:08 pm Post subject:

Chris Card · Guest

Before you start moving the collar on the needle, check that the needle is seating properly. Both the needle and the seat do wear, and that allows fuel to gradually seep through into the carburettor body, irrespective of the float level.

You might find that the pointy end of the needle has a ridge worn in it - this can be dressed out on a lathe, using a very fine file. New seats can be obtained OK. After that, you will probably have to adjust the collar position - mine are just riveted tight onto the needle and are easy to move, others are soldered into position, which makes it more difficult.

Chris