Interested in Thoughts - new pistons and rings or just new rings

[mswyka]

I have some 340 pistons and jugs that measure within tolerance.  I could throw a new set of rings on the old pistons or swap in another set of pistons and rings.  Both options seem equally difficult to find these days.  Thoughts?

[Lloyd (ljm)]

 Hey Mark

 My opinion, and remember it is worth exactly what your paying for it,
 On a 340 I would do which ever I found first. On a 440 it isn't much more money for new pistons than it is for new rings.

 Are the rings on the pistons you have completely done? I have heard of people taking the glaze off rings and reusing them.

[mswyka]

Lloyd, and valuable insight it is.

I am not sure that I really know how to gauge whether rings are done or not.  My sense -based on the fact that only one of the multiple sleds that have come into our shop initially came in under its own power - is that if I have the sled, the former owner probably ran it until it wouldn't run any more.  So to give it the best chance of running again, fresh rings on a new or old piston are probably in order.

 Hey Mark

 My opinion, and remember it is worth exactly what your paying for it,
 On a 340 I would do which ever I found first. On a 440 it isn't much more money for new pistons than it is for new rings.

 Are the rings on the pistons you have completely done? I have heard of people taking the glaze off rings and reusing them.

[Interceptor398]

Check the ring gap.  On the 340 it is .008-.028, if it is on the low side of the gap I would run them.  If it is .020 or higher I would go with the new ones.  The manual shows a new 340 piston diameter of 2.3602-2.3610 and a service limit of 2.355 on the skirt of the piston.  Since 340 Invader pistons are no longer made if it met the service limit I would run it.  As stated before this opinion is worth what you paid for it.  Good Luck!!

[gixxer6]

When I build a motor, I always do a compression test before pulling it apart.  Then I pull the engine apart and do a visual inspection of the pistons, rings, and cylinder walls.  If they are in good shape, and compression is good, run it.  Just keep each cylinder, piston, and rings as a matched set.  If it ain't broke, don't fix it!