150???? I'm not doubting your facts at all. I just find it surprising. Many
years ago, I got my (stock) car up to where it topped out, on a very long
straight away.... As best I could figure, slightly down hill, it was just a
bit over 110 mph. At that speed, the front end was extremely light, and
exhibited a lot of skate. I don't recall taking it above 80 mph since. I just
figured the shape of the 3000 front end was piling a lot of air under the car
at those speeds.
David W. Jones
'62 Mk II BT7 tricarb
Cumberland, RI USA
----- Original Message -----
From: Chris Dimmock
To: James Lea
Cc: healeys@autox.team.net
Sent: Tuesday, April 26, 2005 9:30 AM
Subject: Re: SHE"S GOT LEGS>>>
Hi James
How hard you push your car is your personal decision. I was really just
trying to point out that 'top speed' in our road going cars is generally a
function of maximum rpm and gearing (diff/ overdrive and wheel diameter).
Maximum top speed (for most mortals**) gets simplified into the diff ratio -
how hard you can rev the engine - and how long the road is.
My car makes less horse power at 6,000 rpm than it does at 5,500 rpm - but
then again - if you're already in overdrive top at 5,900 - you don't have
any more gears to change up into - and if you haven't run out of road
yet......
The key things about the C series 6 cyl engine is that there are two bad
harmonics - someone may remember the numbers better that me - a minor at
just under 6,200rpm - and a serious one at around 6.400 rpm or thereabouts.
Don't go there. Or if you do - don't stay there.
I usually change gear at around 5,500 - 5,800 on the track. Depending on
whats going on - probably 3,000 - 5,000 on the road.
My engine specs are here: http://www.myaustinhealey.com/dyno_sheet.html
I was really trying to say that the diff ratio x max rpm does makes the
maximum top speed difference - and a major change in one or the other will
dramtically affect your top speed. Probably the best example of this was at
Bathurst 1998, on Conrod straight. Denis Welch was pulling over 7,800rpm in
overdrive top down Conrod straight - and he had (from memory) a 4.1:1 or a
4.3:1 diff ratio. That is getting pretty close to a 150 mph Healey 3000.
Best
Chris Dimmock
www.myautinhealey.com
**I'm not a terminal velocity enthusiast - but Keith Turk on this list is -
and I'm sure he can explain more about the function of aerodynamics,
friction, and drag once you get past talking about production based cars on
roads!.
----- Original Message -----
From: "James Lea" <clocks@midcoast.com>
To: "Chris Dimmock" <cd3000@bigpond.net.au>; "Dave & Marlene"
<rusd@velocitus.net>; "WILLIAM B LAWRENCE" <ynotink@msn.com>
Cc: <healeys@autox.team.net>
Sent: Tuesday, April 26, 2005 4:28 AM
Subject: Re: SHE"S GOT LEGS>>>
> Chris. Wow!! I guess I am a bigger chicken than I thought. I don't think
I
> have ever had the engine over 3500 and that is rare. Even thought it is
> completely rebuilt I get nervous when the engine revs get over 3000. I am
> I
> just being too careful? How far can I push it safely on the expressway
for
> long periods of ? Thanks, JL
>
> James Lea
> 2 West St
> PO Box 25
> Rockport Me.
> 04856
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