RPM - Gearing - Redline

[Ron Earp]

I'm comtemplating a rebuild of my 907 motor in the JH depending on what I find when I tear it down for inspection.

The little Lotus motor has a stroke of only 2.72 inches, which, if you observe a mean piston speed of 4000 ft/min as limiting will give you a redline of 8800 RPM.

I regularily turn the Lotus 2.2 turbo motor in my Esprit to 7500 with no ill effects so I think this one will take it too. Using the stock rear end ratio this gives me a top speed in top gear, 1:1:

@7000RPM 123 mph

@7500RPM 132 mph

@8000RPM 141 mph

Roughly speaking. Now, I don't know enough about the various tracks to know what sorts of top end one needs. Does this look fine, or do I need to shorten the gearing for less top end, or make it taller for more?

I have no idea if the little car will even make it that high on the lengths that we're dealing with. It is just I have the rear end out, have another one I just bought, and wish to know if I need to start looking for some gears now since it will likey take me some time to turn up alternative ratios for a Healey.

Ron

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
BMW E36 M3
RF GT40 Replica
Jensen-Healey: IT prep progressing!

[apr67]

123 should be enough at 90% of the tracks, if not all.

[JIgou]

Ron--

Try giving Tom Kraft a call at his shop here in Des Moines - 515-287-3007. He used to run a Jensen-Healey in Production (DP maybe?), and while it's a different class than you're heading to with IT, it's still prepping a Jensen-Healey. (I'll let the old-timers have the opening of "what Production used to be is what IT is now".)

You can tell him I sent you if he wonders how the heck...

Jarrod

[JeffYoung]

Ron, I'm back in town.

You will need 130+ mph at VIR, the backstraight at Road Atlanta and Charlotte. At CMP, Roebling and Barber, you won't see more than 115 or 120 or so.

Jeff