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SU HIF-4 runs too rich ('73 MGB)

To: @auschs, @ibmchs.UUCP, @cs.utexas.edu.UUCP:djd@aurora.arc.nasa.gov
Subject: SU HIF-4 runs too rich ('73 MGB)
From: bcarter@gama.austin.ibm.com
Date: Tue, 8 Oct 91 15:03:40 CDT
>>Daniel writes:

> Sometime in the first hundred miles the first carb started to run
> rich.  That's the problem I can't correct.  The engine is fine.  I've
> done the 100-mile valve adjustment and head retorque and have
> proven (?) that the carb is the problem, there's no oil fouling and the
> electrical system (points, timing) is ok.

>The carbs are type SU HIF-4

>Here is a summary of changes to the carb.  Before the new engine:
> -Misc. gaskets plus a good cleaning
> -New needle and seat assembly (jets)

> New parts on this carb since this problem started:
> -metering needle (but not the spring, out of stock) on both carbs
> -float and lever (lever looked pitted)
> -jet assembly (plastic looked cruddy)
> -dust seals on the throttle shafts
> -jet bearing gasket

I had the same type of problem after rebuilding my SU HIF-4s on 77MGB.
it was a devil to figure out. Seeing how I had just rebuilt my carbs
I really didn't suspect them. I checked all other avenues, and ended up
at the carbs again. What I found was that the float in the forward carb
was filled with petro. I still do not know to this day why it filled
with petro and caused the engine to run rich. There were no marks on the
float to indicate damage.

The question I have for you is, have you installed Grosse jets, or just
the standard type? you could have gotten some dirt in there and causing
to much fuel to be supplied. My other question which may be redundent is
have you checked the floats since installation? I know it is a pain but...

No real answers but a few comments and theories. 


Good luck

Bruce...



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