Miata Mailing List: February 2000, Message #528

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Fletch,
According to my Mazda workshop manual which is for a 1991 1600cc, it states
that the pistons should be measured at right angles to the pins at .650
below the oil ring land lower edge. A new standard piston should measure
3.0690 - 3.0698". No wear limit is given. Piston to cylinder clearance is
0015 - .0020 when new and max limit is .0060". It is not stated where this
measurement is to be performed although the illustration clearly shows it
being taken 90 degrees from the wrist pin. It would seem to me that the most
wear would occur on the lower skirt at this position opposite the wrist pin.
Steve


----- Original Message -----
From: "Fletcher Blades" <fletch@powerlink.co.nz>
To: "Multiple recipients of list" <miata@realbig.com>
Sent: Wednesday, February 02, 2000 11:55 PM
Subject: Checking piston/bore clearance.


> Can some-one with a factory manual look up and see what it says about
> checking piston to bore gap with feeler gauges?
>
> My non-miata specific books indicate you "usually" measure the gap at the
> skirts, ie. 90 degrees in relation to the pin.
>
> The Miata enthusiast manual says "measure several places, and see what the
> biggest gap is"
>
> Well, the biggest gap is right inline with the wrist/gudgeon/piston pin...
> and its bigger than allowed... But the skirt measurement is well within
> spec.
>
> So, I want the factory manual's suggestion on weather I need new pistons
or
> not.
>
> I'd rather use the existing pistons, for financial reasons, but if I've
got
> to get new ones, I might as well go over-size...
>
> Thanks in advance,
>
> Fletch.
>
>
>