Ring Pack Thickness: Question

[BadSS]

Not to complicate matters anymore than they already are. However if you don’t think you really need a forged crank or forged pistons, and don’t need to run a lot of RPM for an extended length of time you would come out with a lot more power with the same or less money going with a cast 3.75 or 3.8” crank, running the 5.7 rods you have, and an economical set of 5/64” ringed hyperucrackit pistons. Probably would be able to find all that in stock also.

Not advocating, just saying.

[skinny z]

Piston's ring lands, not the deck.
Ring shim, like on oil rings to bridge a high pin bore or repair worn & re-machined lands, not a stamped steel single piece gasket some call a shim.

Misunderstood what you were commenting on. The conversation had swing over to shim steel head gaskets and I just kind of ran with it.
As for ring land shims, seems to me best route is the proper piston.
But as stated, the issue is inventory.

[skinny z]

Not to complicate matters anymore than they already are. However if you don’t think you really need a forged crank or forged pistons, and don’t need to run a lot of RPM for an extended length of time you would come out with a lot more power with the same or less money going with a cast 3.75 or 3.8” crank, running the 5.7 rods you have, and an economical set of 5/64” ringed hyperucrackit pistons. Probably would be able to find all that in stock also.

Not advocating, just saying.

Funny you should say that.
This whole conversation started in another thread about a replacement piston proposed by my shop. It was pointed out that it has 5/64ths ring and it would be shameful not to step up to something more modern along with the benefits that go along with it.
I've found a hypereutectic piston with a 1/16th ring but it too has shipping delays.
I already have a balanced assembly with a GM forged crank and Elgin rods which were part of the original Speed Pro hyper piston package that I raced for several years. (This is rebuild of that).I found an equally weighted piston replacement, another Speed Pro but with thin rings, but the shop commented on how heavy it was at 700+ grams (with pin). He'd like to go with a lighter piston (Wiseco I believe are under 600 grams) but that'll entail a rebalance.
As for application, it may well be that I'll visit an open road event or two sometime down the road. Certainly drag racing. And plenty of highway miles. Nothing super stressful (the open road racing notwithstanding) and RPMs limited to 6500. Cam spec with the current heads are showing a peak HP RPM of 5900. Overspeed will probably see 6500.

[rebelyell]

How much do shims affect rings?
Couldn't you use narrow rings in any piston with them?

Yes you can.
But the decks require a certain spec surface and flatness to guarantee no failures. I may not have that deck.

At this point in the saga ... It seems you May Not actually KNOW what shape your deck(s) are in. It May be they are Perfect.
OTOH, and regardless which gasket you might compensate with, your Deck(s) may Require cutting/milling.

And, if that be the case, you could run any cheap, Short rebuilder piston you can find.

[ClassAct]

Not to complicate matters anymore than they already are. However if you don’t think you really need a forged crank or forged pistons, and don’t need to run a lot of RPM for an extended length of time you would come out with a lot more power with the same or less money going with a cast 3.75 or 3.8” crank, running the 5.7 rods you have, and an economical set of 5/64” ringed hyperucrackit pistons. Probably would be able to find all that in stock also.

Not advocating, just saying.

Funny you should say that.
This whole conversation started in another thread about a replacement piston proposed by my shop. It was pointed out that it has 5/64ths ring and it would be shameful not to step up to something more modern along with the benefits that go along with it.
I've found a hypereutectic piston with a 1/16th ring but it too has shipping delays.
I already have a balanced assembly with a GM forged crank and Elgin rods which were part of the original Speed Pro hyper piston package that I raced for several years. (This is rebuild of that).I found an equally weighted piston replacement, another Speed Pro but with thin rings, but the shop commented on how heavy it was at 700+ grams (with pin). He'd like to go with a lighter piston (Wiseco I believe are under 600 grams) but that'll entail a rebalance.
As for application, it may well be that I'll visit an open road event or two sometime down the road. Certainly drag racing. And plenty of highway miles. Nothing super stressful (the open road racing notwithstanding) and RPMs limited to 6500. Cam spec with the current heads are showing a peak HP RPM of 5900. Overspeed will probably see 6500.

Well crap. If this is the case, I’d take the thin rings and the heavy pistons. The piston weight isn’t nearly as big a deal as the ring is. Think about it. As the piston comes to a stop at TDC on the exhaust (because there is no load on the piston) the ring wants to keep going up the bore and off the top of the piston. The lighter the ring, the easier it is on the ring groove. There’s way more to thin rings than just that, but suffice it to say that when you add up all the benefits of thin rings it makes piston weight far less important. This is just my opinion. And millions of passes and miles were put on heavy pistons. It’s not like you want to shift at 8k.

[skinny z]

At this point in the saga ... It seems you May Not actually KNOW what shape your deck(s) are in. It May be they are Perfect.
OTOH, and regardless which gasket you might compensate with, your Deck(s) may Require cutting/milling.

And, if that be the case, you could run any cheap, Short rebuilder piston you can find.

Saga?
Ask a simple question and get 8 pages in reply. Yeah. Maybe a saga.
But the build is simple except for parts availability.
Knowing this engine as well as I do, and at the last refresh it was still square, I'm of the hope that's still the case.
If it isn't, I'll deal with it.
If it's still tight...did I mention I was looking for pistons...?

And I do want to say thanks for all of contributions to the thread. It certainly sparked some interest.

[skinny z]

Well crap. If this is the case, I’d take the thin rings and the heavy pistons. The piston weight isn’t nearly as big a deal as the ring is. Think about it. As the piston comes to a stop at TDC on the exhaust (because there is no load on the piston) the ring wants to keep going up the bore and off the top of the piston. The lighter the ring, the easier it is on the ring groove. There’s way more to thin rings than just that, but suffice it to say that when you add up all the benefits of thin rings it makes piston weight far less important. This is just my opinion. And millions of passes and miles were put on heavy pistons. It’s not like you want to shift at 8k.

I'd mentioned I'd come across a newer version of the piston that was in it after searching through all of the forged options. Same weight too with better rings. Hypereutectic and heavy.
Now in conversation with the shop, the builder was surprised at the weight. He went so far as to recommend looking for a lighter piston. (Looking some more that is).
This is when the conversation stopped because now being from a simple 40 over, polished crank and out the door, there's a rebalance. And whatever else.

Now, all of that said, and with the contributions here and elsewhere, I've got the direction dialed in.
Just have to wait on parts. And it'll be one of two piston choices based on hours of poking around.

[Bill Chase]

The right cam will always overcome heavy rotator with thick rings.

Wouldn't the benefits be even better with the modern light weight rotator and modern ring pack though? If the goal is performance and longevity the cost difference is really not that bad. Mahle, wiseco both make a decent affordable piston kit now days.

[skinny z]

Unless the supply chain shifts dramatically, and pending further discussion with the shop (we've only met face to face once when I dropped off the crank and piston/rod assemblies), I'm inclined to simply go for the replacement Speed Pro hypereutectic piston (1/16th, 3/16ths rings), skip the need for a rebalance, and get on with it.
If the shop or anyone else can put up a more compelling argument as to why the Wiseco would be a better choice, I'm all ears. Other than lighter, which is better, and a forging, which is debatable given the history this engine has seen with the original hypereutectic pistons, the Speed Pro looks to be the way to go.

Screenshot_20220126-064427.png

Screenshot_20220126-064513.png

Remember that it's also an availability thing as it is anything else.

[skinny z]

Unless the supply chain shifts dramatically, and pending further discussion with the shop (we've only met face to face once when I dropped off the crank and piston/rod assemblies), I'm inclined to simply go for the replacement Speed Pro hypereutectic piston (1/16th, 3/16ths rings), skip the need for a rebalance, and get on with it.
If the shop or anyone else can put up a more compelling argument as to why the Wiseco would be a better choice, I'm all ears. Other than lighter, which is better, and a forging, which is debatable given the history this engine has seen with the original hypereutectic pistons, the Speed Pro looks to be the way to go.

The compelling argument came from the shop owner.
When discussing the machine work he said that he'd investigate the balance regardless of my piston choice. The logic is that he doesn't know what it is to begin with and he'd be remiss if he didn't address it. So, whatever the piston, I'm in for a balance job. Or close to it anyway.
Cue the Wiseco piston in all it's glory.
Done and dusted.
Now we'll see how his personal supply chain works out. I can easily wait a couple of months or more before the shortblock lands in my "shop". It'll be all indoors in this part of the world for a while yet. Like May...