Stihl 660 piston skirt re: “I made a mistake”

[drf256]

Or a cheater bevel in just the plating, arching the plating rather than the whole port, so that the height isn't affected any noticeable amount.

That is another good cheat.

 

[NPKenny]

I ordered a Meteor 288xp piston on Saturday night from HLSupply. I'll post back once the piston arrives.

 

[NPKenny]

It’s been a while. Here is an update. I touched up a bit of the port work and need to decide where to go from here

I installed the Meteor 288 piston, using a 13mm pin and a crossover roller bearing (395xp, I believe) to match the 12mm crank.

The pistons are quite a bit different. The 660 piston is noticeably taller with the crown lower wrt the pin height. I had to remove approximately 0.035” more from the base to obtain a squish of 0.021”.

The numbers at this point are:
Exhaust 98*
Transfers 125.5*
Intake 78*

26.5* blowdown seems like a lot. I can raise the transfers some, but the uppers seem huge.

I plan to finish the intake at 80-82* and would appreciate some input.

I was able the curve roof of the exhaust slightly and went from 100* to 98*. Due to the shorter 288 piston, there is a slight freeport at the bottom of the exhaust. The exhaust has given me a run for my money on this saw.

Pictures…

Piston pin differences. 288 on left, 660 on right. Both Meteor.


Piston total height difference.


Exhaust roof, 98*.


Intake with export. Currently at 78*.


Exhaust freeport at bottom.

 

[NPKenny]

Part numbers for the piston pin and crossover bearing.

 

[NPKenny]

This saw will do most cutting at 5k - 6k feet elevation. I’m trying to create a plan for compression and case compression. This is basically a salvage effort at this point. I might as well do the best I can.

 

[Junk Meister]

This saw will do most cutting at 5k - 6k feet elevation. I’m trying to create a plan for compression and case compression. This is basically a salvage effort at this point. I might as well do the best I can.

Any MORE content ?? A CURIOUS READER is wondering if you managed to salvage this project.