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Re: Carb & Trans Oil Questions

To: "Christian, Skip" <>,
Subject: Re: Carb & Trans Oil Questions
From: "Kai M. Radicke" <>
Date: Thu, 8 Apr 2004 14:14:35 -0400
> I will probably junk the HIFs and install HS4s.  The thing about the
> SUs I like the most is their simplicity and the HS series work fine
> and are the most basic.  Unless someone can tell me why the
> HIFs are better (a lot of people have told me to keep the HIFs, but
> no one has provided a good reason), I plan to switch to HS-4s.
> Anyone - why are HIF4s better than HS4s (not including
> emissions) ?????
> Skip '74 B

The HIF series of SU carburettors is an improvement over the older H and HS
series.  Here are the reasons:

On the positive side...
1)    They flow more air, typically 5-10% more CFM than the earlier models.
2)    The integrated float bowl means fewer fuel feed issues during extreme
autocross conditions or other race conditions.
3)    The bi-metallic strip makes slight compensations in the fuel mixture
depending on air temperature.
4)    I personally feel they are more durable and reliable year after year,
when in good condition, than earlier SU carburettors.
5)    Better fuel economy when the carburettors are setup up correctly.

On the negative side...
1)    Increased complexity, but, if you understand it, you'll get more out
of the HIF carburettors than the H/HS series of carbs.  So this is a
positive, if you like the HIF series.
2)    Increased cost.  Replacement parts and rebuilds are more expensive.

Hope that helps your decision.


Kai M. Radicke
Wishbone Classics

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