I can't answer all your questions, because I'm not that familiar with
the HIF4 carbs (or the Weber, for that matter), but I can help with some
of your questions.
I'll probably hear some disagreement on this, but, unless you're doing
some racing, I would go back to the original SUs. You won't notice much
difference in regular daily use, as long as the carbs are clean and
properly tuned. The SUs were made for your car, so why not use them?
Instead of looking for a shop to work on the carbs, why don't you do it
yourself? It's really not that hard. I picked up the Haynes SU Carb
manual (there are others on the market too) and rebuilt mine, following
the instructions in the book, mostly because I could not find a decent
mechanic that could get them running right. That doesn't mean they
aren't out there, but I would bet you would do a more careful and
thorough job, simply because they're your carbs. The carbs were the
first thing I ever did on my LBC and, believe me, if I can do it,
anybody can.
Some of the important things to check for, on any SU rebuild is: check
for wear on the throttle spindle and bearings, the needle, and the jet.
Make sure the flat faces are not warped, and check the piston and the
inside of the suction chamber for scoring and corrosion. Also check the
needle valve and float in the float chamber. There are other things,
but these are the biggies. When in doubt about a part, replace the part
- it's worth it in the long run. Above all, the most important thing is
cleanliness! Clean carbs run much better than dirty ones, so make sure
everything is spotlessly clean!
I'm not sure what the spring-loaded shaft is that you're talking about -
My manual doesn't show it, but it might be pictured in a good MGB manual
(should have a picture of the hose layout too). On my Midget I have the
throttle shaft & choke shaft (which lowers the jets).
I'm also not sure about the induction heater? A quick glance at my carb
book doesn't mention that (and my car doesn't have it). I'm guessing
they're calling it something else in the book, or they don't consider it
part of the carbs, so it's not in te book. Can you describe it? Is it
one of those cold start devices? Those are in there and I could look it
up for you. Sorry I couldn't help more.
-Nory
'74 Midget & '71 parts car
'94 Ford Ranger
'85 Ford Escort
'89 Ford Probe
'96 North American Shepherd
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