Jarrid says:
"I think the resulting power band was usable torque between 2500 and 5500 RPM.
Thats a pretty wide operating band, quite usable for the street, and puts
the power well within the design margins for the engine"
Yes, then we all agree!
Kristian J
----- Ursprungligt meddelande -----
Fren: "Jarrid Gross" <jgross@econolite.com>
Till: <Jay_Laifman@countrywide.com>; "Bruce Davis" <phyrman5@earthlink.net>
Kopia: <alpines@autox.team.net>
Skickat: den 20 maj 2003 17:58
Dmne: RE: Torque or not more torque
> Jay and piners.
>
> The holbay H120 engine is a paradox.
>
> The published cam timing data would suggest that it is a higher
> RPM engine due to its overlap and duration, only that it also has
> a lot of cam advance.
>
> Advancing the cam yeilds more low end torque, so what you seem to have
> are competing strategies between high and low rpm opperations.
>
> When you through the added compression that the flat top pistons gave,
> and the vastly improved porting, I think that the net result favored
> the mid range operation. The H120 clearly was done making power
> at 5500 RPM so its definately not a high horsepower engine.
>
> Why the H120 produces more horsepower than the stock 1725 is twofold.
>
> 1) The engine produces more peak torque, at a slightly higher RPM than
> the stock 1725. This is from the compression and webers.
> Horsepower is a measure of work done, and making torque at higher RPMs
> does more work, hence more horsepower.
>
> 2)
> The small ports on the H120 simply would not have flowed the amount needed
> to make a 6500 RPM engine, but much like header designs, the smaller port
> diameters shifted the induction resonance to a lower RPM, which would
> reinforce the cam timing.
> The competing strategies between the cam advance and the overlap
> reinforces the power band to be the compromise between the two.
>
>
> I think the resulting power band was usable torque between 2500 and 5500 RPM.
> Thats a pretty wide operating band, quite usable for the street, and puts
> the power well within the design margins for the engine, which made it
> a popular combination for rally racers that actually wanted to finish a race.
>
> As to the lugging issue, Its never a good idea to "lug" a high compression
> engine as its hard on the rod and main bearings. If the driver knows better,
> than 3.70 would be fine.
>
> I am pretty sure though that my comment about 3.70 and lugging related to
> fitting an overdrive in which case even a 3.89 might be excessive.
>
>
> Jarrid
>
>
>
>
>
> -----Original Message-----
> From: owner-alpines@autox.team.net
> [mailto:owner-alpines@autox.team.net]On Behalf Of
> Jay_Laifman@countrywide.com
> Sent: Tuesday, May 20, 2003 8:16 AM
> To: Bruce Davis
> Cc: alpines@autox.team.net
> Subject: Re: Torque or not more torque
>
>
> Well, what you are describing is what Rootes did to the Holbay engine, and
> exactly what I was saying. You are giving up on high end power for low
> end power. Nothing is free in this balance. Remember, the original
> Holbay set up was 120 hp, but when they got it to the street it was only
> 105 hp. Part of this was the result of doing what you described,
> narrowing the intake, and part from the change to the cam (which also
> reduced breathing) - but all the loss of high end power to gain lower end
> drivability. Even to this day, nothing has changed. Take the Honda S2000
> for example. Wild total power, but all at the higher rpms. Just look at
> the figures on various cars. The higher the power on a same size engine,
> the higher in the rpm it indicated at. Nothing is free. Of course the
> geniouses at Honda have come up with all sorts of new ideas to keep some
> power down low.
>
> My point is still that throwing on the Holbay head, cam and Webers does
> not make the Alpine a low rpm torque puller - and a 3.7 rear end could
> cause too much lugging on the engine. Remember that Jarrid sometime ago
> was arguing that even a 3.89 might cause too much lugging on a Holbay
> engine.
>
> Jay
>
>
>
>
>
> "Bruce Davis" <phyrman5@earthlink.net>
> 05/19/2003 07:54 PM
> Please respond to "Bruce Davis"
>
>
> To: <Jay_Laifman@countrywide.com>
> cc:
> Subject: Re: Torque or not more torque
>
>
> Remember, with 2 identical motors and you cause the intake to be either a
> wee bit longer or narrower, you will cause the charge to go into the motor
> at a higher speed which will equal more torque. That is why you get better
> low end power by delaying the intake
> opening.......................................................OK I am not
> a
> rocket scientist but I believe this is correct.
> BAD
> ----- Original Message -----
> From: <Jay_Laifman@countrywide.com>
> To: <alpines@autox.team.net>
> Sent: Monday, May 19, 2003 5:52 PM
> Subject: Torque or not more torque
>
>
> > "Together with the Holbay camshaft and the correct Webers and right air
> > filter (look up! the carb set-up is very sensitive to the air filter)
> you
> > get a torque engine. Its not a high RPM engine! This suits the 3.77 rear
> > end with overdrive gearbox."
> >
> > I do not think this is 100% accurate. In general, if you take two
> > identical sized engines and try to increase power to one of them by
> better
> > breathing and carberation, that brings on power at the higher rpms at
> the
> > expense of the lower rpms. On the other hand, if you take otherwise
> > identical engines and increase the size of one of the engines, you will
> > gain that power and torque at the lower rpms. So, by going the Holbay
> > route, you generally lose torque and power at the lower ends.
> >
> > Jay
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