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High ring pistons and broken rigns

K

kakon864

Member
So I've got my share of 70's Evinrude v4's (6 of them). I have noticed that a lot of the times they have broken piston rings. I did some research and found that they are all prone to breaking rings, but ones with "high ring" pistons are especially as likely. I cannot find what a high ring piston is/looks like but I am assuming, and might be wrong, the piston ring is closer to the top than normal? How can I tell if the piston is the high ring design or not?. I also read that if you have the high ring design to fully retarding the full advance timing by 4 degrees to prevent piston ring breakage.
 
If you come across a "High Ring" piston, there will be no mistaking it.

There is only a few thousands of a inch between the top of the piston and the ring itself.... such a short distance that the top edge of the piston becomes hot, curls up and the ring is allowed to grab the edge of one of the ports.

In inspecting the pistons via removing the 6 bolt intake inspection port covers... if there is 1/8" or more of the piston showing between the top of the piston and the top ring... it is NOT a high ring piston.
 
Re: High ring pistons and broken rings

joereeves said:
If you come across a "High Ring" piston, there will be no mistaking it.

There is only a few thousands of a inch between the top of the piston and the ring itself.... such a short distance that the top edge of the piston becomes hot, curls up and the ring is allowed to grab the edge of one of the ports.

In inspecting the pistons via removing the 6 bolt intake inspection port covers... if there is 1/8" or more of the piston showing between the top of the piston and the top ring... it is NOT a high ring piston.
Click to expand...

Sounds like a pretty poor design. I also got most my info from a reply you made almost 20 years ago lol.
Thanks
 
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