Datsun Roadster Parts from Rallye Enterprises, Ltd.




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.

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.

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...

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