Seeping SU bowel

The bowel on my rear HS4 is leaking. I have replaced the gasket, grose jet and have a new fuel feed line with a good tight clamp. I don't get it. I have tried adjusting the float to a little more and a little less than 1/8" and it makes no difference. The seeping is greater under acceleration load (I can smell the raw fuel).

The grose jet is working because when I removed the bowel cap the pressure in the line from the front to the rear carb was still there (spraying fuel everywhere) until I lifted the float and the grose jet stopped the flow.

Also the tube coming from the overflow is dry. So the grose jet/float is cutting off the fuel.

I am suspecting maybe the gasket is not thick enough. Do you guys use some sort of glue on those thin little gaskets?


This car burned 4 years ago from leaking fuel and it is not moving again until I solve this.

Any/all suggestions greatly welcome!

Ditch the GrosJets and go back to the OEM needle and seats on both carbs.

Jack

Peter, you should not need any sealant on the gasket. Were these carbs on the motor that burned? If so, the carb tops may have warped slightly and if they did it will be difficult to get a good seal.

Jack, do you think those are causing the leaking problem? I have a pair of used SU's in the basement and I might just see what's in them and try a swap. If that works I would order new needles and seats.

Wray, don't think so. Those carbs were shot. BUT I can not promise that I didn't use a lid from them. It was 3 years ago when I rebuilt them and I was swapping parts so I am not sure.

In theory the GrosJets are superior but in practice they are often a PITA. Try the old ones, just make sure that the cones of the needles don't show a heavy groove where they meet their seats, and do keep the sets paired as they come from the old carbs.

Jack

My Grose (gross) valves worked perfectly under every static test I could devise. Once the engine vibration entered in, they seeped. My experience is that they are useless. Some people say you can tap them to seat them - I'm sticking with the old fashioned valves.

Peter, my HIFs were weeping, smelled slightly of gas. I had torqued down the bowl lids too hard and bent them ever so slightly which was enough. I had to replace them.

After talking to Joe C and Hap I used a straight edge on them and could see the bow in the lids.

I realize yours are HSs but you might want to swap a top lid from one of your spare sets and see what you got.

Well how about that!

I put the lid from the other spare set on (with the needle and seat) and it leaked worse than ever. So I swapped the grose jet for the needle and seat and put on a different gasket. NO LEAK. No seep.

Gonna do the front one now because I can see that its gasket is damp too.

Thanks Jack. I'll take it for a spin and see if the engine vibration causes any issuea. But statically under key on fuel pressure, its looking better.

Sometimes the jet will pull right out of the jet tube on hard acceleration. Safety wire the jet in place or add a tight spring to the jet to keep it from leaking. Basil

Basil Adams Wrote:

Peter,
You might want to clean the whole bowl/jet assembly and then turn on your ignition to see if simple pressurization from your pump is causing the leakage and where it is originating from. You may know the source already, but if not, it may be coming from somewhere you haven't noticed because there is too much gas all over to isolate it.

One area that does give folks some fits over leakage is the connection of the jet supply tube to the float bowl. For the small O-ring seal there to work/seat properly, the old seal has to be completely removed during installation, and this does not always happen. Sometimes the complete old seal is left behind during disassembly or it has hardened such that there are remnants left in the float bowl seat and these can cause the new seal to either not seal properly from the get-go or allows a leak to emerge sometime later. The float bowl/jet tube seat really needs as clean as possible before installing a new jet tube connection. You may have done this, but I have encountered too many SUs for which this has NOT been done and a simple clean up with a new O-ring did the trick.

Another, perhaps more remote possibility is that over-tightening of the jet supply tube by a PO to stop a leak has cracked the float bowl casting. I have only encountered this once, but the integrity of any float bowl casting is only as good as how well it was cast in the first place. Small imperfections in castings can cause cracks to radiate from screw and compression fitting mounting holes that only show up when there is some tightening force applied. Altho not too likely, you never know how hard some PO reefed down on a fitting or screw/bolt going into a threaded casting.

No picture, sorry. But the jet pulls right out the bottom of the carb body. I have springs attached to the heat shield and to the jet to keep them from retracting. If you have a manual choke hooked up, the choke linkage will stop that from happening.

I'm surprised no one has said this yet but, wouldn't a seeping bowel leave a brown stain under the carb? :I3:

Peter,
What's your fuel pump setup and pressure (if non standard)?

JoeReed Wrote:

A goodly dosage of some Kaeopectate should cure that problem. Joe, I couldn't resist it any longer :)