4 ring vs 5 ring pistons

[Marvin Gruber]

I'm sure this has been discussed before but guess I was out playing. Building two late BJ8 motors. The later number engine is a 4 ring piston motor and the other is a 5 ring. Would someone explain or give me any facts or history on that. Both are std bore. If the 5 ring pistons are that much better should I swap them to the later engine.

Marvin

 

[Jerry]

5 ring is just more friction, but work very well. I have used both. I think racers use the 4 ring, but most of us don't drive this way.

Jerry

 

[Bob_Spidell]

Modern cars, I believe, use just a 3-ring piston, but usually run 'oversquare' with pistons that have shorter skirts (I believe the top compression ring holds the majority of the pressure). I think the extra ring or two in a Healey engine might provide some stability so the skirts don't slap the cylinder walls. I've wondered if a properly sized 3-ring piston would work OK in the (relatively) long-bore Healey engine (I've heard of builders leaving out the fifth ring).

Randy, you've built more engines than most of us, what's your take on this?

 

[Patrick67BJ8]

Jahns pistons were 3 rings and worked great. I don't think the original 5 ring pistons worked any better at oil control than the others(4 and 3 ring pistons).

 

[Marvin Gruber]

So don't worry about the extra ring. Just found out that I have to sleeve one cylinder, too deep a scar from wrist pin failure. And cost goes on.

Marv

 

[Patrick67BJ8]

So don't worry about the extra ring. Just found out that I have to sleeve one cylinder, too deep a scar from wrist pin failure. And cost goes on.

Marv

Sleeving one cylinder is not expensive. I've had to do that on one overhaul. The sleeves are available.

 

[Marvin Gruber]

Headed to machine shop this morning to sleeve #3.
Marv