Help with Twin SUs fuel leak

[1966 122s]

I have just developed a fuel leak on the twin SUs. I noticed petrol smell when parked up and examination shows petrol wet to touch where fuel line enters. There has clearly been silicone sealant applied by the previous owner which is now falling off in chunks. Apparantly he applied to both carbs (so I could describe this as a "thorough" bodge !) but I believe only the front is leaking. Its lasted 3 years or more but I'd rather not have this bodge dripping fuel onto the heat shield / exhaust !

I'll admit the problem started after me adjusting tick-over and choke in a rather cack-handed manner. The results of the adjustment were that the choke cable had a lot of resistance when used for the couple of days before I admitted defeat reversed my attempt ! Still has more resistance than it used to, so once the fuel leak is fixed I'll have to find out how to do this.

I'm not very technical and I am not familiar with SUs or carbs in general. But I'll have a go at whatever is needed. Hence apologies for asking the basics.

What's the best way forward???


I'll post up photos to try to explain the problem a little better. (My arrow on scan of service manual is probably the best explanation. I wish I had a Haynes manual !) Apologies again for these basic questions ! Thanks

[asneddon]

Buy two new jets and fit them. About £16 each from memory. They include the pipe that is leaking. If the float chamber (the alloy bit the pipe goes into) has stuffed thread, then get a second hand pair of carbs. Probably about £150-200?

Idle is easy, and shouldn't change choke feeling unless you really wind it up.

[amazon69]

I'd bet the thread is ok...those little lines can be a sod to get fully seated, and you can think you've done it and they'll leak..looks like what's happened here.
Always good to get new jets. Get a pair of needles too, about £5 each iirc..big difference.

[Ron Kwas]

?

Normal silicon is not hydrocarbon compatible, and that fitting shouldn't need any sealant anyway. The Seal (25) is a snug fit over the fuel line OD and it is squeezed (out against wall, and in against hardline) as the fitting (23) is tightened (Snug, and to the point of not backing out by itself, only...Do Not overtighten!). Washer (24) is the interface between turning fitting and fixed seal...it prevents damage. Remember, there is only the minuscule pressure of a 2inch column of fuel to seal against!

Leaks are caused if seal to line fit is sloppy. Replace seal. In a pinch, an emergency seal can be cut from fuel suitable line with an ID of the OD of the hardline, and OD of the threaded hole in base of fuelbowl...use old seal as a guide.



Hope that helps.
Cheers from Connecticut!

[amazondean]

A small o ring often does the trick but new jets and needles is the answer. They are incredibly simple to fit. A big deal is made about centralising the jet but all you need to do is wind the jet right up onto the needle while the lock nut is loose. Carefully tighten the lock nut and wind the jet down so that the top of the brass jet is leval with the bridge. (the inside of the carb throught.) Then wind down nine flats. That setting will allow the car to run properly. Small adjustments may be needed for fuel economy but the car will run ok at this setting.

[1966 122s]

Thanks again for the above replies. I've finally had time to start work on this.

See photo:
I have got to the following position with the carbs still on the inlet. (Photo is courtesy of a digital camera stuffed into position. I am reasonably convinced thread is OK from the photo.

Questions:
1. A brass part is visible inside the thread of the aluminium body (see photo). Is the brass part actually " washer 24 " (on Ron's post and diagram above) ???? If so I will pull it and the seal out to inspect / re-new.

2. Braiding cover over plastic fuel pipe doesn't look great. If it turns out that on re-fitting there is a gap of expossed plastic pipe, would this be a risk this close to heat shield exhaust manifold ? (Hopefully I will manage to re-fit without a gap... but this question is a "just in case".)

(Apologies trying to cut corners here !! I'm trying to avoid changing jets or even taking the carbs off as the car is running well and I am petrified of screwing something else up. Everytime I do something for the first time it seems to be one step forward and two steps back. Feel free to read my previous post about changing the timing gear .... complicated by my snaping the end of the cam if you doubt this.) Hence I am attempting to just put in a new o-ring / seal.... or even just re-tighten if I find seal 25 (on Ron's diagram above) is in good condition. I know I should do the whole job, but jets etc sounds daunting.)

Thanks

[AidanC]

You really need to replace that part - anything else involves too much risk to the car. Burlen will post them out or MacNamaras in Fairview will most likely have them

[redcar]

aidanC have you dealt with McNamara's before? if so, what are your views?

[AidanC]

Originally Posted by redcar

aidanC have you dealt with McNamara's before? if so, what are your views?

Mixed - I found them helpful but expensive when I was bought SU parts from them. They know their stuff though and I've heard that they're good at setup if you bring the car to them. I know of someone else who found them good value (for VW Solex jets).

In the context of fuel leaks and fire risk I'd see them as being much cheaper than the worst case scenario. If a quick fix is need then they're quicker than waiting a week for post from the UK.

Have a look at www.wheelspin.ie - a few of us are planning a meet in Roscrea in June this year.

[1966 122s]

Thanks Aidan and Redcar,

I can wait for the parts so will probably go for Brookhouse out of habit. Nice to know there are irish suppliers !

I understand the needles are standard. What jets would match a B18 with D cam (and skimmed head) ?

Does it goe solely by the cam ?