1977 115HP Piston Ring Locating Pin Acceptable Length

Hi all,

Doing a rebuild of this engine, and have two pistons that have worn a locating pin completely away.

A third piston has a pin that has been worn to approx 2.1mm long (0.083"). A new pin is probably 4.3mm long (0.169").

The workshop book I have states simply check for excessive wear, but doesn't state a length.

I have no idea when the pistons were replaced (if ever), so have no idea how long it has taken the pin to wear this far.

What is an acceptable length for these pins?

Thanks,

Nick.

I would replace all 4 pistons right away. Those motors have piston issues that can be fixed right by replacing them with the updated piston.

You need 4 new pistons.

Thanks gents, have ordered 4 new pistons.

Could you let me the reason as to why (just need to know!).

Thanks,

Nick.

You would need to look at the ring grooves.---------They are usually worn and new rings will not seat properly in the PISTON.---If original the ring grooves were too close to the top as well.----------What pistons did you order ?

nicklanigan said:

Thanks gents, have ordered 4 new pistons. Could you let me the reason as to why (just need to know!). Thanks, Nick.

Click to expand...

When the slightest doubt arises pertaining to the piston ring locating pins... replace the piston unless you enjoy rebuilding the powerhead "twice!"

The new pistons will answer your question pertaining to the length of the pin.

The reason to replace...... when the engine is running, and the retaining pin is worn, the piston ring will turn out of place on the piston which allows the end of the ring end to relocate to one of the ports. The piston ring end flips into the port which of course results in major damage... and double work, $$$, down time, etc.