4.1 Piston Rings

[ek02]

I have a set of very good used custom JE forged 4.1 stroker pistons made for 1/16" compression rings and 3/16" oil rings. A ring package does not exist for a 3.995 bore in that ring width. I used 4" JE file fit ductile iron rings (.005 larger) in the past because JE said they would work, and they did for a long time, but I experienced excessive cylinder wear and eventually excessive blow by. If only I knew then that I should have gone with a 4" bore. My thought is to use standard Speed Pro or Sealed Power moly rings for a 4" bore and file fit them for another block I can have bored to 3.995. Does anyone think this will not work?

 

[87GNSteve]

What did you wind up doing about this?

 

[gunzandgearz]

It should work fine that's all the file to fits are is just a little extra material to get ring gap right on, you are achieving the exact same thing with a standard ring and taking .005 off of it.

 

[ek02]

I spoke to the tech department at Speed Pro and he thought that the 4" standard rings would work. I'm still waiting on the block to be girdled and bored. It's been in the machine shop since April due to a lack of personnel. It's supposed to be done in two weeks. File fit rings are not larger in diameter, they just have the gaps extended from what I have read. I used a set of JE 3.965 file fit rings in a block honed to 3.972 with ceramic coated pistons, and they worked perfect. I am sure the 4" standard rings will be OK. I found a guy that has some Diamond Plasma Moly rings for a 3.995 bore that are 1/16, 1/16, and 3/16. They are apparently left over from a special order, maybe for a 4.1 Stage II Busch engine? I should have them by next week. I'll check the fit in one of the good round cylinders in my old block. Custom rings can be made, but it is big bucks to do it. If anyone needs a set of 3.995 rings, I'll post the info when I am sure the rings are correct.

 

[ek02]

I got the Diamond 3.995 file fit rings today. The top ring is plasma moly, second ring ductile iron J ring (groove on the outside of the bottom of the ring), and low tension oil rings. I have never used a J ring or low tension oil rings, so I will need to research it some. Looks like the second J ring is to scrape oil from the cylinder walls. It has a ledge on the bottom of the outside of the ring. I put a 3.995 file fit in the cylinder and the gap is 0. I put a 4" ring in the same bore and the gap is 0. I placed one 3.995 ring on top of another standard 4" ring and I don't see any difference in diameter. I believe either ring will work when file fitted. Edit: I found out the J hook second ring is a napier ring and should work OK. Not sure about low tension oil rings though.

 

[gunzandgearz]

Yep shouldn't have any problems.

 

[87GNSteve]

Does that guy have any more of those rings? how much did you pay for them?
I found a set of Hastings moly but they are 4.000 I need to decide soon.

 

[ek02]

Here is the E Bay link. http://www.ebay.com/itm/Diamond-Pis...ash=item2a3020c854:g:MjoAAMXQwwlSCoaZ&vxp=mtr They are 89.95 plus 9.95 shipping. He has 4 sets left. The price is right. I may get a spare set once I decide if I want to run a low tension oil ring. Unless you already have 3.995 pistons, I would go with 4" pistons and rings on a 4.1.

 

[87GNSteve]

Thanks for the info. I have the pistons already.

 

[ek02]

I have done some reading on low tension oil rings. They are usually not recommended for boosted applications. What makes an oil ring low tension is the expander. The Speed Pro oil rings I have look like the expander puts more pressure on the rails than the Diamond expanders. The low tension expanders are made to pretty much just hold the rails with almost no tension. The Speed Pro expanders are made to put tension on the rails. The rails are the same on either set. The second ring being a napier ring should help oil control with the low tension oil rings. The main reason the low tension oil rings are not recommended for boosted applications is because any oil in the combustion chamber could cause detonation. Most new car engines come with low tension ring packages, though. I have a set of expanders from a Speed Pro ring set that I could use in place of the Diamond expanders, but then there is the napier second ring that may not work well with higher oil ring tension. I'll have to wait and get my block back so I can maybe see how many pounds of pull there is on the piston with the Diamond rings versus the Speed Pro's. There are many different levels of low tension oil rings from what I have read.

 

[87GNSteve]

I planned on using the oil ring set from the Hasting set I have, not going to use low tension oil rings in my application and I like to use heavier weight oil.

 

[TexasT]

I planned on using the oil ring set from the Hasting set I have, not going to use low tension oil rings in my application and I like to use heavier weight oil.

Not to get too far off topic, but why do you favor heavier weight oil?

Sent from my HTC PH39100 using Tapatalk

 

[gunzandgearz]

Im curious about this too, the objective is to run the thinnest oil you can get away with that will still get the job done.Its kind of like racing fuel you want to run the fuel with the least amount of octane that the motor can tolerate without detonating, because as you go up in octane, this slows down the burn rate of the fuel and makes less power.

 

[87GNSteve]

This engine will be used in an endurance road racing application and the tolerances were built to the max specification.
I am willing to sacrifice some power/economy for increased protection.

 

[ek02]

I called Diamond tech support today. The guy I talked to said that the low tension rings in this set should be used with a vacuum pump evacuation system. He said using regular tension oil rings and the napier second ring will work OK. He said the difference in a 4" ring and these 3.995 rings is not enough to matter. I plan to use the expanders from a Speed Pro ring set I only ran for a few hundred miles with the rails from the Diamond set, the Diamond napier second, and the Diamond Plasma Moly top.

 

[turbofabricator]

The napier ring IS an oil control ring, not a compression ring. Top ring is compression ring, second ring is an oil control ring. Run thinner oil. No need for thick oil if you control bearing clearances. (and pump clearances)