1956 5.5 Johnson re- ring job, ring gap specs

[dockrat100]

I bought a 1956 5.5 Johnson about a year ago, and at the time, it was said to be operational. i pulled it in the shop to start going through it, and the powerhead was locked up. I dissembled the powerhead and got it freed up, but I wanted to replace the rings in it. The problem is, the old rings fit in the cylinder with .020 of ring gap, the manual says that .015 is max. I have not honed the cylinder yet, which will probably open it up a few more thousandths.

What should I do with it now? Oversize rings?

 

[HighTrim]

Re: 1956 5.5 Johnson re- ring job, ring gap specs

Correct, and .015 is the upper end of that scale, .005 to .015 is acceptable.

Before making any other decisions, first determine what is going on with the bore. Ensure it is still round and honable.

With the original piston in the bore, what is the wall clearance, should be within .0013 to .0025.

Your cylinder bore should be 1.938"

If you do need to oversize piston and ring, the 020 piston part number for you CD is 376427 and the 020 ring set part number is 378417

 

[dockrat100]

Re: 1956 5.5 Johnson re- ring job, ring gap specs

For the price of pistons and rings, if they can be found, I should be able to locate a used powerhead with good compression ,no?

 

[boobie]

Re: 1956 5.5 Johnson re- ring job, ring gap specs

Don't use over size rings with a standard piston and bore.

 

[nwcove]

Re: 1956 5.5 Johnson re- ring job, ring gap specs

not sure if all your work will be worth it without checking all the other moving part clearances. a replacement powerhead from a good source may be a better option. jmo

 

[dockrat100]

Re: 1956 5.5 Johnson re- ring job, ring gap specs

I think I will donate my old powerhead to a local Physics teacher, so he can use it to explain engine basics to kids, and use the replacement powerhead for this project.

I found a donor powerhead on aomci, and though rebuilding one sounded fun at the time, I think the more prudent course of action will be to buy the powerhead and get on with life.

 

[boobie]

Re: 1956 5.5 Johnson re- ring job, ring gap specs

Good choice........