what size rings for my pistons

[twkjr 1250]

how can i tell if they are standard. I can't find any numbers on the old ones. the motor is 69 mercruiser gm block 4cylinder 3.0 serial #2770087

 

[Fishermark]

Re: what size rings for my pistons

Measure your bore and see if it is standard or not.

Why are you replacing the rings if I may ask?

 

[Fishermark]

Re: what size rings for my pistons

By the way - looking at your picture - when you get that engine back together, be sure to get rid of the inline fuel filter. It is not needed and can cause issues with safety. Go ahead and replace that line either with another metal fuel line, or type A1 marine fuel hose.

 

[twkjr 1250]

Re: what size rings for my pistons

they were seized up oil rings freed up , compression rings i soaked in mystery oil for a week . had to remove in peices. 2 down 2 to go . by the way this was newly rebuilt 6 years ago and only test run once on muffs. also cleaning up valve stems 2 vof them were sticking. what do i use to measure bore size standard.

 

[Fishermark]

Re: what size rings for my pistons

You can use a dial bore gauge.... but if you do not have one, it will be cheaper and easier to drag the block down to your local machine shop and ask them.

How do the cylinders look? Rusted and pitted? May at least need to be cleaned up with a hone if nothing else.

 

[twkjr 1250]

Re: what size rings for my pistons

that filter was their probably because both fuel tanks are no good . rusted out right below pickup tubes. Hate galvinized tanks in a boat, and for the lines they are trash anyway no choice in the matter copper sounds like the way to go .

 

[twkjr 1250]

Re: what size rings for my pistons

cylinders look pretty good compared to the rings . I have 1 cylinder with pitting 1" from the top ofa cylinder. but plan on alight honing to clean them up abit more. One of the rod bearings was gauged . looks like the shaft got a burr from a peice of something from the rebuild the other guy had done.

 

[Aloysius]

Re: what size rings for my pistons

the pistons will have the oversize stamped on them unless they're stock bore.

 

[twkjr 1250]

Re: what size rings for my pistons

so i should be looking for .10,.20,.30 ect.. i imagine on the inside will look now

 

[twkjr 1250]

Re: what size rings for my pistons

thanks got it now it was on top . don,t know how i missed it all the time i spent cleaning them up anyway. std for standard, bigger than daylight

 

[Aloysius]

Re: what size rings for my pistons

that's it!

Now, before you install the rings on the piston, make sure the end gap is adequate..rule of thumb..0.004" per inch of cylinder diameter. 0.004 too much won't make any difference; 0.004 to little will destroy stuff. Put the ring in the cylinder, square it with a piston upside down, measure with a feeler gauge.

 

[Eric 3.7LX Alpha 1]

Re: what size rings for my pistons

I've bought rings as "file fit" as well that come oversized and require/allow you to create the clearance you desire by filing them to the correct gap, depending on your application.

You have to buy a ring grinding tool to do it.

But I would think as long as you measure the gap as mentioned above on the std. rings before installing, you should be all set.

 

[Aloysius]

Re: what size rings for my pistons

Cylinders wear more at the top than the middle..the bottom never wears. Use a point at the bottom of the ring travel to measure and fit the rings!

 

[twkjr 1250]

Re: what size rings for my pistons

thanks for that install info. i looked and found my rings on the web , but they need to know the width of the ring grooves on the piston does this sound right

 

[Aloysius]

Re: what size rings for my pistons

sure. But why buy online? If it's someone that advertises on this site, great...support them! Otherwise, deal with a local supply house, where you can make sure everything is correct.