Datsun
Roadster Parts from Rallye Enterprises, Ltd.
1600
PISTON INFO The
dome tops give the engine it's 9.0:1 compression
ratio. You
can also use a flat top piston in your engine, which has
advantages and disadvantages. The flat tops will give
reduced compression pressures (unless the head has been
milled a lot) If your head hasn't been overmilled this
may allow you to run easier on a lower grade of gasoline.
If your head HAS been milled a lot it may allow you to
still run comfortably on premium without using an octane
additive. Sometimes in the size you want only a flat top
is available. When
a 1600 head is milled, the "pocket" that the dome mates
with is cut away. After about .030" milled off it is
necessary to recontour the chamber to allow clearance for
the piston dome to reside. Using a flat top piston allows
you to skip this operation. (Original 1600 head thickness
is 3.248 +/- .002. Since
head milling is usually done to correct warpage, this
problem is normally going to be on the far ends of number
1 and 4 pockets in the head. If you have been trying to
diagnose a "tapping" problem you may notice the head is
shiny on the outbound edges of the end chambers. You just
squeaked by, what can happen is the car actually starts
cold, but as it warms up everything expands until the
engine actually locks up. The
correct way to deal with this is of course measuring what
has been taken off the head at a given location and
recutting the chambers properly by laying a gasket over
the chamber and tapering the chambers out as before. This
will ensure the correct intake/exhaust flow and burning
characteristics are retained. Sometimes the domed pistons
are less expensive too. I'm
glossing over the fact that ANY engine that has the end
chambers of it's cylinder head cut will not run as
smoothly or efficiently as an engine with all cylinder
head chambers equalized. In a typical
surface-the-warped-head scenario, the end chambers end up
being cut far more then the 2 center chambers.
If
you have been trying to solve engine noise problems and
the noise is more of a ringing, like a church bell, that
can sometimes be a loose flywheel.
The
original pistons for the "R" 1600 have a mild dome top.
They may appear to be flat, but they are not. If you look
at them sideways, or run the piston up to TDC in the
block, or put one upside down on a table it becomes
apparent rather quickly that they are not perfectly flat.
CHECK WITH YOUR MACHINE SHOP BEFORE ORDERING RINGS AS
THEY CANNOT
BE RETURNED. "Unopened" or Opened. It is extremely
easy to damage rings by improper installation on or
removal from a piston. Would YOU like to be the next
buyer of a set that has been improperly handled and that
won't peform as expected? I think not...