It sounds like the pistons are standard Nissan 1.00mm overbore. Where did you
measure the piston
diameter? See http://oemcomputer/machinist.asp
There shouldn't be any notches on the pistons. Do they look machined?
If the Jahns pistons have valve marks even with reliefs, it makes me wonder if
the head has been
milled. If your engine is still reasonably together, clay the pistons and see
what kind of
piston-to-valve clearance you've got.
andycost@att.net wrote:
> I had a knock that sounded like it was coming from the
> piston pin on the #1 piston so I pulled the motor and
> tore it down. The pistons were stamped with a 1.00-F
> marking on the top and there were small (1 cm) notches
> in the edge at the front and back of the top of the
> piston. I measured the pistons and got 87.75 mm. The
> Datsun Sports manual I have lists a 100 overbore with
> the size as 88.270 mm. Upon manipulating the rod and
> piston I can find no slop at the pin. The rod bearing
> has some very shiny worn places and an area where the
> copper shows through. How do I determine if the pin,
> piston, or the rod top bushing are bad? Why do the
> measurements not match the factory manual? What are the
> notches for? They don't appear to be valve reliefs.
> These pistons appear to be three piece units with some
> kind of inserts the wrap around the skirts on the
> inside. I have a set of Jahns high compression pistons
> that are the same size. I have not been able to find
> out anything about them. They do have big valve
> reliefs, but they didn't help the PO. All four of them
> have impact marks form the intake valves. I was
> thinking of grinding the impact area a bit and using
> them. This car will be for autocross and I have access
> to all the (free) aviation fuel I could ever need. (I
> work for a lab that tests diesel/gas/jet fuel etc...)
>
> Thanks,
> NT
--
Gordon Glasgow
http://www.gordon-glasgow.org
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