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Re: piston to deck height?

To: datsun-roadsters@autox.team.net, jt_milton@yahoo.com
Subject: Re: piston to deck height?
From: walter@omni.sps.mot.com (Thomas Walter)
Date: Sat, 16 Oct 99 09:07:52 CDT
Joshua,

It is a really good idea to check out the compression ratio
while rebuilding the engine.

I do not have a piston to deck height measurement for the 1600.
Usually I set the piston to TDC, use a "ring" with a top cover,
then fill the volume up with a pipette (I have a 50 cc pipette
for this reason).

With the known volume of the "ring and hat", I calculate the
difference in volume to know the offset.

Then on to the cylinder head, same thing is measuring the
volume.

Do not overlook the 'displacement' of the head gasket. 
About 0.060" x area. 

Static C.R. =  (Swept volume + displacement) / displacement.

So if you measure 40 cc of displacement volume, on a 400 cc
swept volume you have a compression ratio of 11:1 -- really
too high on pump gas.  For 1600 engines sometimes it makes
sense to drop in a 2000 piston (flat top).

Using the 2000 cc piston, you'd get a total displacement of
50 cc. Compression ratio is ((400+50)/50) 9:1.

The above numbers are GUESSES. Just to give you an idea of
the calculation.

WITH A 1600 ENGINE:

When it comes time to reassemble, I'll get the cam set up
to the correct installation. 

TEMPORARY install the head WITHOUT a head gasket. Just finger
snug the head bolts down. Install the push rods and rockers.

Rotate the engine by HAND... everything OK?

If you can rotate the engine by hand, you'll be fine. Once
the head gasket is installed, it has about a 0.060" clearance.

WITH AN OLD HEAD GASKET: I'll repeat the above, but with some
thin putty on the top of piston, and a old (previously compressed)
head gasket installed. It is interesting to see the actual clearance
from valves to piston.

Hope this if of help.

Cheers,

Tom Walter  '67 2000
Austin, TX  '68 2000
            '93 Dodge Dakota - 3phase 288V electric powered!
            '99 Nissan Maxima 
            {Also a '63 Bluebird Sedan, and '71 510 4dr)


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