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SU HS4 carbs on 68 MGB/GT

Subject: SU HS4 carbs on 68 MGB/GT
Date: Mon, 4 Feb 2002 15:06:08 -0600
Just as a followup, I wanted to update the list on the outcome since so 
many of you offered very helpful advice to my carb problems. 

First, on the problem of the needle valves in the float chambers sticking 
open and gas streaming from the overflow pipes, I'm happy to report that 
it is fixed.  Not a drop of gasoline from the overflow pipes.  The culprit 
was apparently particles of dirt getting stuck in the Grosse jet valve 
(which I replaced the original needle valves with).  After installing an 
inline fuel filter and (once again) thoroughly cleaning out the float 
chambers, the problem was solved.    No fuel pressure regulator was 

I also found that the reason the car had been so difficult to start and 
run was because one of the jets was frozen stuck in its bearing in the 
carb (this car sat in dry storage for over a decade).  Therefore, the carb 
with the frozen jet was exceptionally lean and would not choke at all. And 
the other carb was adjusted fairly lean anyway, so after disassembling 
them, cleaning them, and replacing the frozen jet and bearing, I adjusted 
the fuel/air mixture to a slightly richer setting.  Presto!  The car 
starts easily (even on a frosty morning) and purrs like a kitten.  Even 
cold, it revs up smoothely.   I love these SU's!  They are a marvel of 
simplicity and reliable engineering if you just take the time to 
understand what is going on inside them.  I think the mixture is now 
slightly too rich, but I'll deal with that later. 

Now I have a stripped down B/GT in primer with no doors or glass or 
interior that runs pretty well.  I even took it for a short drive around 
my cul de sac (slowly, since it has questionable brakes).  Thanks again 
for the advice!
Greg Hutmacher
1968 MGB/GT 
1976 Triumph TR6

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