[TR] TR4A Piston Upgrade

[MMoore8425 at aol.com]

In a message dated 9/6/08 11:30:42 PM, 308gtsi at roadrunner.com writes:


> Well, I did go with the 87mm upgrade when I rebuilt my 4a engine last year,
> but not sure it was worth the extra $$$. It is a bit self defeating - the
> larger the piston, the more mass; the more mass, the less revs. And we all
> know revs = fun! Ever see the inside of a Ferrari engine? The pistons are
> about 50mm, but they get some serious revs and HP out of those things.
> 'course there's lots of other stuff that helps too.
>
> Anyway, I'd say if I were to do it over again I'd spend the money else
> where... like maybe overdrive! :-)
>
>
> I'm sure Randall will have some good words of wisdom on this subject...
>
> Brian
> '67 TR4a
> Just won 1st place in my class at the Portland All British Field Meet! Time
> to sell???
>
>
>
> ------------------------------
>
> Message: 5
> Date: Sat, 6 Sep 2008 15:31:43 -0700 (PDT)
> From: Pat Caffrey <pcaffrey at deltacollege.edu>
> Subject: [TR] TR4A Piston Upgrade
> To: triumphs at autox.team.net
> Message-ID:
>     <28406311.480721220740303817.JavaMail.root at hermes.deltacollege.edu>
>

Brian,
When I rebuilt my TRA several years ago, I bored to 90mm and had pistons
made. THAT was a little pricey to. Wit a little bigger cam etc it scoots right
along. I would probably not do it today because it is a waste of mony. It goes
very well, but sounds just like my neighbors Harley at idle. I don't really
care
if my 0-60 time is any better as I'm not racing it.
You are on the mark on pistons size though-the torqu is related to piston
diameter (area) but the RPM is going to be affected more by the inertia pf the
rotating mass which is really a diameter cubed function (piston mass) qhich s
why those little bitty v16s do so well.
Best. MIke Moore
(I would probagly go with 83mm today


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