I should add that yes, the Holbay head did not have intake runners this
large. My mechanic opened them up to match the Weber throats. And,
again, my car is very tractible and responsive at the low end too. I'm
not convinced that Rootes/Holbay did the right thing in the first place,
especially given the nice running I have.
Taking it one step further, where I'm bound to trip, intuitively, it seems
wrong. The issue is the size of the throats of the carbs for the size of
the engine. It's like blowing with your mouth wide open versus with your
lips puckered. That makes sense to me. But, to restrict the flow after
the carbs have already mixed the atomized gas with the air seems like a
misplaced cure that basically kills the very benefit in the first place.
If the carbs were so incorrectly big, they should have started from the
top with smaller carbs. But, from my experience, I don't think they were
too big either. Again, as I said, with this step, I will probably trip.
Jay
"Jarrid Gross" <JGross@econolite.com>
11/25/2002 12:04 PM
To: Jay_Laifman@countrywide.com, alpines@autox.team.net
cc:
Subject: RE: Weber intake size and alternator information
Jay wrote:
>Someone asked me the size of my Holbay head intake inlet size. That is,
>the size it was opened up to to match the 40 DCOE side draft Webers. I
>can't find that e-mail. Sorry. So, everyone gets the number. I measured
>it at 32.7 mm in diameter.
The 32.7mm runner diameter is quite large. I doubt the stock holbay head
had such large runners, becuase this was contradictive to the strategy
that
Holbay was after in the tuning of the H120 engine. The strategy seems to
have been to keep the port velocities high, and utilize the valve-train
reversion to give higher volumetric efficiencies as lower RPMs.
Larger ports are great at higher RPMs, but probably not so good for the
camming strategy from the H120 cam.
It is my understanding that the stock H120 head used slightly smaller
exhaust ports, and the same sized intakes as compared to stock.
Jarrid Gross
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