Rings for mild blown application

[FC-Pilot]

Putting together a mild blown BBC. Will be an 8 to 1 489 on pump gas. Will have a 871 at 1 to 1. It is going in a v-drive boat that will not get much use, and I doubt much if any full throttle use. Anyway, due to the fact that the customer is not much of an engine guy I was planning on going with a plasma moly ring set as I have had great results with them seating quickly. Any real reason that I use anything else? If there is strong reasons I can be persuaded, but have had two occasions where rings for boosted applications did not seat well do to the customer not putting any real load on the engine.

Feel free to share reasons or ideas as I am all ears. The pistons were ordered with 1.5,1.5,3mm ring grooves (as an FYI).

Paul

[Mark O'Neal]

Moly rings are fine. I've never had an issue under about 20 lbs of boost. Like anything else it boils down to tuneup.

I pretty much always use a steel ring when i can, if it's easy to do, and doesn't cost any more than the moly set. There's no reason to put a $300.00 ring set in this one.

[F-BIRD'88]

Build it and set it up as if it will run at WOT ALL THE WAY ACROSS THE LAKE AND BACK AGAIN.. wide open.

Cause it will.

[ProPower engines]

Build it and set it up as if it will run at WOT ALL THE WAY ACROSS THE LAKE AND BACK AGAIN.. wide open.

Cause it will.

I totally agree with F-Bird 88!.
Boats are a different animal. Mark does know lots about pistons but my concern as a builder is most boaters never really
get the fact that engines are under extreme load at cruising speed and the cooling systems allow for the block to get cooled but the internals like the pistons not so much and the top ring takes all the abuse from heat.

Yes a moly ring will work fine for so knowing the limitations of what they have and others again not so much.
For this type of application I would use a steel top ring and lateral gas ports. Or if its in the budget go with an AP steel gapless top.
Again be aware of the amount of back space you have behind the top ring if you are mixing and matching a combo as the extra heat generated in a boosted engine will grow the top ring much more then a regular N/A combo.

Just curious what pistons are you going to use in this build??

[dannobee]

And don't forget to put a little extra gap in the rings too, lest it heats up and pulls the top of the piston off.

And put some high quality valves in it, too. For the same reason as above; they're GOING to run it flat out. It WILL build some heat. REAL stainless intakes and probably inconel exhaust valves if they can afford it. Better yet, just do it and don't give them the option of saying no.

[FC-Pilot]

Actually I got the pistons from Mark (through my machinist). The boat is a light weight drag boat (v-drive runner-bottom, Cole TR6). It will not be run wide open for miles at a time as it is being built mainly as a show boat for a father and son to cruise on the lake to the v-drive gatherings. Most guys not on a race course won’t even run their stuff for a full 1/4 mile as the longer it stays under full power the greater the chances of an involuntary swim increase. I understand needing to open the gaps for the increased heat as well as the extra clearance due to running cool lake water for engine cooling. I recognize the reality that in a marine application there is continual load on the engine that a street car does not see, and the need for better parts as such. I appreciate the comments guys. Thanks. Any other comments in regards to what I might have forgot are also welcome. “I ain’t too proud”.

Now if this were for a pleasure boat it would get steel rings and I would put it in the dyno. Because it does not fall into that category I am willing to make an exception. Like I said, I have used AP rings before and had seating issues when the owners never put a load on the engines as they just putted to the sand bar and drank beer and talked about how fast the boat “could” go.

Paul

[engineguyBill]

1.5mm; 1.5mm; 3.0mm is a good ring package for this application. TOP GROOVE: steel ring with plasma moly face; SECOND GROOVE: grey cast iron Napier style; OIL ASSEMBLY: Standard tension flex-vent style. I have had good luck with the Perfect Circle/MAHLE ring sets with these features.
I wouldn't worry about gas-porting the pistons, as it is not really beneficial in this application.

[Walter R. Malik]

Hard coated, faced steel rings seem to work very well in high heat, detonation / preignition prone situations.