What's on your bench today?

[spudulike]

5 thou is very good, 7 -15 thou typical, 20 is getting knackered. Obviously a single ring is more prone to compression loss than a double.

[bmp01]

10 minutes ago, spudulike said:

5 thou is very good, 7 -15 thou typical, 20 is getting knackered. Obviously a single ring is more prone to compression loss than a double.

Ring end gaps, yes ?

I was attempting to put a number against the subjective piston to bore clearance.....obviously not very clearly. Cor blimey, just imagine 12000rpm, a piston clanking around with 20 thou clearance.... 

[spudulike]

Sorry, I was talking ring end gap clearance and not piston to bore.

I have seen some piston skirts shattered down to excessive piston slap through wear. The MS260 was one culprit!

[billpierce]

Well with the ring pushed square down the bore an inch I can fit the feeler gauge which says 100 on it through the smallest part of the gap and that's the biggest one I have. Think that means 1mm gap as its .05mm to 1mm guage so reckon that means worn right?

[billpierce]

Just answered my own question! Thanks for help so far! Piston skirt doesnt seem to rock much 

[openspaceman]

24 minutes ago, billpierce said:

Well with the ring pushed square down the bore an inch I can fit the feeler gauge which says 100 on it through the smallest part of the gap and that's the biggest one I have. Think that means 1mm gap as its .05mm to 1mm guage so reckon that means worn right?

That's 40 thou; way too big a gap by a factor of 5, lots of gas escaping.

[openspaceman]

Does the gap change as the ring is moved up and down the bore?

[spudulike]

My experience is measuring at the base of the bore and never seen 40 thou on any machine. That is massively worn!!! 7-15 is fairly typical with 20 on a well used old machine being normal!

The cheapest fix would be to get a decent quality piston...OEM, Meteor, Hyway, Episan and fit that making sure it is set to rev as a 350 would be. Check the plating is still good on the bore and lightly hone to accept the new piston.

 

 

[billpierce]

9 hours ago, openspaceman said:

Does the gap change as the ring is moved up and down the bore?

Have not checked but will do so

[billpierce]

9 hours ago, spudulike said:

My experience is measuring at the base of the bore and never seen 40 thou on any machine. That is massively worn!!! 7-15 is fairly typical with 20 on a well used old machine being normal!

The cheapest fix would be to get a decent quality piston...OEM, Meteor, Hyway, Episan and fit that making sure it is set to rev as a 350 would be. Check the plating is still good on the bore and lightly hone to accept the new piston.

 

 

Nikasil looks ok on the pot. Any good places for rings? Only seem to be cheapos from China on Ebay or cabers from the states