Jim and Andy,
I am virtually certain it is an error. Although I erred on my statement
too; 0.003 to 0.010 is correct, Jim.
The general rule of thumb is 0.003 for every inch of bore diameter. Racers
often go 0.005 for every inch of bore diameter, to account for additional
carbon buildup (I think). 0.003 on a 3 inch bore (3 inches=75mm, let alone
a 83 or 87mm) would most likely result in broken rings. This is what I
learned from the list and other resources when I did my emergency re-ringing
patch job last spring. The paperwork from Deves, the ring manufacturer
supported this belief.
BTW as a plug for Deves, their pre-gapped 83mm rings consistently end gapped
at 0.011 to 0.013 in the unworn section of my bores. This is the bottom, or
tighter end, of their tolerance range.
Jack
> -----Original Message-----
> From: JIM_WALLACE@HP-Canada-om1.om.hp.com
> [mailto:JIM_WALLACE@HP-Canada-om1.om.hp.com]
> Sent: Tuesday, December 29, 1998 10:37 AM
> To: amace@unix2.nysed.gov; brooks@belcotech.com; triumphs@autox.team.net
> Subject: TR2-4 Piston ring gap specs
>
>
> Andy, Jack,
>
> My Haynes says "Before fitting the rings on the pistons each should be
> inserted approximately 3 inches down the cylinder bore and the
> gap measured
> with a feeler gauge as shown in fig 1.17. This should be between .015 and
> .038 inch. It is essential that the gap should be measured at the
> bottom of
> the ring travel........" This is in the text on page 36, in section 32.
>
> In the specifications on page 15 however, the gap for the TR2,3, or 3a is
> given as 0.003 to 0.010 (not 0.0010), and for the TR4 or 4a as 0.010 to
> 0.015.
>
> What gives? I thought at least that the 3a and 4 engines were the same
> thing, and anyway, all these numbers are different.
> Can someone shed further light on this?
>
> Thanks,
> Jim Wallace
> TR3 TS81417
> ********************************************
> From: Andrew Mace <amace@unix2.nysed.gov>
> Subject: Re: TR2-4 Haynes manual errors
>
> On Mon, 28 Dec 1998, Jack Brooks wrote:
>
> > ...Are there any known errors beyond the TR2-3A piston ring gap
> > dimension?
> >
> > The above mentioned error is the piston ring end gap for the TR2,3,3A
> which is incorrectly listed at 0.003 to 0.0010 whereas the TR4 gaps is
> 0.010 to 0.030. The correct TR2-3A numbers are closer to 0.009 to 0.028,
> the values supplied by Deves, the ring supplier for Moss.
>
> If that range IS in error, then it's an error carried over from the
> factory's own Service Instruction Manual, p/n 502602.
>
> - --Andy
>
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