ATWEDITOR@aol.com wrote:
> I'm at work now and can't check on that dent question, but let me gas
> on about the last two.Last year Grassroots Motorsports did a series
> of dyno tests of bolt-on MGB engine mods. One of the huge shocks
> from their point of view was the difference--around 4%--made by
> bolting on stub stacks to the mouth of the SUs, and letting them
> reside under K&Ns, which also provided a power gain of around 4%.
> Unlike standard bell-mouthed velocity stacks, the stub stacks are
> about 1/2 in. high with a rounded opening edge that, as dealer ATF
> products (I think that's their name--information also at home) says,
> provides "a nice radius" for the SU carb opening. In short, I guess
> it just fools the air flow into thinking the carb is bigger, and the
> flow is increased. Cast versions of the stacks are around $19 each,
> and that's what Grassroots tested. When I ordered mine, the cast
> versions were out of stock, so I got the billet versions for around
> $30 each. I also got K&Ns at the same time, ! going for the open
> element design that eliminates the metal pots. I am here to tell you
> that the combination of K&Ns and stub stacks makes a SIGNIFICANT
> difference in performance throughout the power range, from lowest
> RPMs up to readline, and yes, it seems to allow the ancient B engine
> to keep accelerating at higher revs where previously it seemed to run
> out of gas. The bill--around $200 and 15 minutes install time. So
> here's my ultimate cheapie, no-risk, quick-install performance boost
> recommendation: A Petronix ignition, K&N filters and stub stacks.
> Buy, bolt and burn. Jay Donoghue72 B-GT66 Mustang (also with Petronix
> and K&N)
My experience confirms this; I have a single HIF6 SU on a special
manifold on my Cooper S. I experienced a noticeable performance increase
when I added the K&N cone filter with the short stub stack inside.
-Rock http://www.rocky-frisco.com
--
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