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Home > Beginners Tech > Realistic rpm max and final drive

NealfromNZ

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29 Posts
Member #: 1961
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Wellington New Zealand

Have a Austin 1300gt engine running forged pistons 7.9 cr , standard gt rods / flywheel , 255 piper turbo cam , 13 stud head , double valve springs, s rockers. Gearbox internals are St ratio backlight, and I have an abt diff.
Turbo is a smaller IHI VJ unit which I'll allow up to 12psi. Hoping for 130 BHP.

Engine is going into an old 1964 mini 7 which I'm converting back for club tarmac based motorsport running on 165/70/10s

Anyway, I'm thinking 6500 rpm would be a realistic max but interested in peoples experience.

If this is realistic was thinking of 3.4 final drive to achieve 100 - 105 mph in 4th for those long straights.
Am I close too the mark or am I dreaming ?


stevieturbo

3393 Posts
Member #: 655
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Northern Ireland

rpm ability will be down to crank, rods, pistons, camshaft etc etc.

Certainly for an A+ based turbo build even with standard parts...I'd consider 6500rpm a pretty low upper limit.
Some 20+ years ago when I ran mine, I regularly seen 7500rpm with no issue at all.

Although how bearable yours will be for whatever journeys you do is another matter and entirely personal.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


D4VE

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2910 Posts
Member #: 10749
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lowestoft suffolk

Mine is there and ive only hit it once, but its all down to individual engine imo

On 24th Oct, 2015 jonny f said:
Nothing gets past Dave lol

NOTHING GETS PAST ME!! *tongue*

1/4 mile 14.7 @ 96mph 12psi boost
Showdown class A 2nd place 18.6 @ 69mph


NealfromNZ

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29 Posts
Member #: 1961
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Wellington New Zealand

Thanks, for the replies. Main use will be motorsport events and no doubt most of its life spent below 100 mph. Would like to enter a targa event where some of the roads would see max rpm in top on quite a few sections. Thinking 110 115 would be limit of power verse air drag if taken out to 7000 rpm. Turbo sweet spot looks to be 2200 to 5000 ish.


minimole23

4196 Posts
Member #: 1321
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Bristol

I would be tempted to fit an ultralight flywheel and backplate to loose some weight off the end of the crank. Sounds like with the power tailing off 7k will be about the limit.

On 7th Oct, 2010 5haneJ said:
yeah I gave it all a good prodding

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