four rings on piston?

[Brayab]

I am replacing the rings on an engine I am rebuilding 1964 170.

there is a fourth slot at the top of the piston

it is filled with hardened carbon that i can't wash off or even pry out

I can't find out any info in my sources

any ideas?

I am planning to put it together the way it is?

 

[mannella]

A photo would help

 

[Brayab]

here's a pic

I attempted to scrape out the carbon on one piston

I tried for 45 minutes and did not get all the carbon deposits out

 

[Thad]

That looks like the partial grooves one on each side of the piston for oil to escape from between the piston and cylinder bore during down stroke. As piston goes up oil from crank is splashed up onto cylinder walls. On down stroke bottom oil ring wipes cylinder wall, accumulated oil needs to escape or rings will skate on oil losing seal. The reason that you can't clean the groove completely because there is part that is real shallow and not a real groove.

 

[Brayab]

sorry, not the greatest picture, it doesn't look like four grooves at all

the groove closest to the table is the one filled with carbon deposits

I took the the rings out of the other 3 grooves

 

[mannella]

I agree I think what you are calling the third ring slot doesn't go all the way around the piston. I assume there were no rings in it? Are you using a broken ring to scrap out the carbon in the top slot?

 

[Brayab]

I tried to take some better pics, they are FoMoCo standard bore

I am going to replace them, I found some on ebay for under $100

the crap in the last groove will probably start falling out once I get it running

still seems weird to have that groove and no ring, it is a crud catcher

 

[69.5Mav]

Brayab

Please post a picture of a piston with the rings still installed or re install them.

I have seen the carbon ring before. In an older engine of mine the number one piston lost have the ring. Carbon filled in the empty spot left by the missing ring piece.

I think some one installed the rings wrong.

 

[Brayab]

one of the pistons had lots of damage on top it looked like a piece of metal got banged around inside of the cylinder

lots of dents on the top of the piston

I purchased the set off ebay for $75 and $12 shipping

is it possible to install the wrist pins myself?

I see a tool in the service manual but I guess it would be really hard to get hold of one?

 

[bubba22349]

is it possible to install the wrist pins myself?

The pins are interference fit so you would need press to remove the old ones. Than to install the new ones a press fixture or a rod heater, unless you have use of a good size press or are planing on doing a number of engines it would be less expensive to have the pistons hung at an auto machine shop

 

[69.5Mav]

Any chance of a picture of the Piston with the original ring installation?

I think some one installed the rings wrong. Your piston looks like a standard three ring piston. Most auto pistons are three rings. The only place I ever heard of four rings being used is on diesel engines.

If I'm right about this that engine probably ran like crap.