Piston brand identification

[healey8390]

I need to id my pistons because I need re-ring 3 of them and replace one of them. Im buying a wiseco but need to know what brand they are so i can buy the right rings for the other 3. There are no id marks at all but each piston has 3 lines about 1/8 thick around the whole piston skirt about equal distance apart. I KNOW that engine was torn into because #1 and #2 pistons have 2 rings and #3 and #4 have 3 rings but they are the same brand and i cant tell if theyre oe. Its a 1983 4cyl 90 chrylser. My camera crapped out so I dont have pics.

 

[Frank Acampora]

Re: Piston brand identification

As far as I know, there is no way to identify brand of pistons.

One thing I can tell you is that your 4 cylinder 90 is a derated 105. When the standard was changed in 1982 to prop shaft horsepower, Chrysler simply called the 105 a 90.

IN 1983, Again, as far as I know, there were NO stock pistons with three rings. So, yes, that engine has been opened. It may be that the pistons were replacwe with whatever was lying around. Are the rods matched?

If the other three pistons do not appear to need rings, then don't replace them. If compression on those three is 100 or better, there is no need to re-ring.

 

[healey8390]

Re: Piston brand identification

Thanks frank. I acutually found a video on youtube with a force rebuild and his pistons had the three lines like mine and i contacted him and he said they were oe. He also recommended not to change the rings on the good cyls becase a force expert told him that the rings and pistons wear together. I just figured since it was open to re-ring any way so I dont know what ill do. But before it blew i have my comp readings written down. 1-4, 128,130,134,135. And im guessing that #3 and #4 have better comp because of the three rings. Do you think i should only put 2 back to balance the engine out???

 

[Frank Acampora]

Re: Piston brand identification

The three lines or bands around the piston skirt Versus two lines or bands, or even no band, make no difference at all. The fine grooves in the skirt (knurling) reduce piston drag on the cylinder walls and retain more oil for better piston skirt sealing, thus better crankcase compression to blow more air/fuel into the cylinder.

However, I read your original post to mean that two pistons had three piston RINGS installed. This is old style and as far as I know, no newer engine uses a three ring piston.

Three rings don't seal any better than two rings, especially if the three rings have the gaps in line and the two rings have them on opposite sides of the piston, and a 5 pound difference in cylinders is not significant. With these 2 cycle engines, a fresh charge of oil is introduced with each revolution and significant part of that oil is on the rings and cylinder walls. That, coupled with the fact that these engines get relatively little running time means that short of problems, piston rings just do not wear out. So, usually, unless damage to the piston or cylinder has happened, which means that the piston will need replacing anyway, the engine will not need a "ring job."

Three rings will produce slightly more drag internally, but not enough that you would notice. Additionally, there is no "Balance" problem with mixing piston types. So go on and happily use the three ring and two ring mix in your engine.

(Personally, I would not do it because it offends me aesthetically--I'm anal, obsessive-compulsive, and Mr. Monk is my mentor and hero. I would not be able to sleep nights knowing that there were different pistons mixed in the same engine block. ---But, that's me. LOL)

As far as not replacing one of the rings in a three ring piston---I have often wondered about EXPERIMENTING with USING only the top ring in a two ring piston and letting the bottom groove fill with oil during running--- Just to see what happens to compression and power.

However, in your case, unless you are willing to experiment and are open to the possibility that you may need to do more work to replace the missing rings, I would re-install each piston with the correct number of rings it requires.

Here is a photo of three old style stock pistons with not only three "bands" around the skirt, but three piston rings.