Ring Pack Thickness: Question

[skinny z]

For a performance build 355 SBC shooting for 450-ish HP, I certainly wouldn’t be paying much of a premium for having an extra skinny ring pack.

"Extra skinny" being the operative phrase there.

Seems there's a general consensus that it makes no sense to run anything wider than a 1/16th. Going for 1mm seems a little extreme.

[skinny z]

Gas mileage doesn't matter much when on the next block you're going to hammer on it anyway.

While there's some element of truth in that I will say that previous projects have driven from Alberta to Ontario and back several times. It's nice knocking down some decent MPG when you on a 5000 mile round trip.
And plenty of pep for passing.

[swampbuggy]

Skinny Z, there is No reason to be afraid of using 1 mm rings ( top and 2nd ) . Everybody is becoming convinced that thinner rings are just fine. I guess it has already been mentioned in this thread, but if not , the Factory Engines are being fitted with thinner rings. The Auto manufactures did not just decide at a given point, lets put thinner piston rings in our Engines and hope it turns out good. They "always" do Research on things like this before mass production. Cylinder roundness and proper cross hatch is obviously of extreme importance, and there must be a load / resistance on the Engine to cause the rings to seal up . Mark H.

[PRH]

For a performance build 355 SBC shooting for 450-ish HP, I certainly wouldn’t be paying much of a premium for having an extra skinny ring pack.

"Extra skinny" being the operative phrase there.

Seems there's a general consensus that it makes no sense to run anything wider than a 1/16th. Going for 1mm seems a little extreme.

Sure, if you’re buying pistons anyway........ get something with thinner rings.
However, If the current pistons are “fine”, I would definitely find a different place to spend the money than new pistons.

[swampbuggy]

Yes PRH, the big question is , how far down the road is he on his engine build ? Mark H.

[skinny z]

At this stage it's a known that 40 over is in the cards.
So know having found a well represented shop to do the work, we're sourcing parts.
Pistons are at the top of the list.
Availability is proving difficult.
The Wiseco piston is the target at this point.

Now I'll throw a spanner in the works here and see what your educated minds come up with.
This engine will be carbureted.
Do you think with the often excessive fuel wash that comes from a carb, and it does happen particularly on cold starts, is going to kill those 1mm rings?
And to add to the debate, as it's been touched on here already, what is a half a millimetre in the difference going to provide?
1/16th (1.5 mm) vs 1 mm.

[ClassAct]

At this stage it's a known that 40 over is in the cards.
So know having found a well represented shop to do the work, we're sourcing parts.
Pistons are at the top of the list.
Availability is proving difficult.
The Wiseco piston is the target at this point.

Now I'll throw a spanner in the works here and see what your educated minds come up with.
This engine will be carbureted.
Do you think with the often excessive fuel wash that comes from a carb, and it does happen particularly on cold starts, is going to kill those 1mm rings?
And to add to the debate, as it's been touched on here already, what is a half a millimetre in the difference going to provide?
1/16th (1.5 mm) vs 1 mm.

No. Thin rings last LONGER. Tune up your carb. And .020 makes a difference. A 1/16 inch is .0625 so a .020 change is almost 20%.

I watched the Hidden Horsepower podcast with Larry Morgan. You should go watch it. He will tell you how much longer thin rings live. And you’ll also hear him tell you how he could have been 10 years ahead of everyone, but fear held him back.

Me? I’d wait on pistons and get something worth having. Rushing through a build is what a broke assed teenager does. Delayed gratification is real. There is price and there is value and they are different. One is far more important that the other.

[rustbucket79]

Rustbucket79, with appropriate and due respect, you kinda shot from the hip. Have you heard that old saying ? This ( my ) Engine will have ( 4 ) Scavenge sections 1.700" wide pulling vacuum in the Dry Sump Oil Pan. We are looking for 20 " , and there will be oil sprayed at the bottom of the pistons to insure that the wrist pins stay well lubricated . Mark H .

Sorry I didn’t see mention of a dry sump in that post.

[rebelyell]

Yes PRH, the big question is , how far down the road is he on his engine build ? Mark H.

yes again & again & after so many machinations ... when will actual assembly begin ? when ???

[rebelyell]

Vortec motors did not & do not come with thick rings; iron L31 continues to manufactured. Both then ('96) and now: OE 1.5mm 1.5mm 3 mm.

I wasn't really thinking about the L31 crate engines. More like the OEM production versions. And I didn't know the ring technology went back that far. More like a result of the LS explosion.
Thanks for the insight.
Seems also that the 1.5mm / 1/16th wide rings went a lot of miles.

It's crazy to think that a difference of 1/64th" made such an impact (5/64 vs 1/16).

The production iron Vortec 5.7L L31 motors ('96-'02 vin code "R") all come OE w/ the thin ringpack; as do their replacement L31 currently available via GM powertrain.
Thinner GM production ringpack pre-date Vortec L31.

[skinny z]

At this stage it's a known that 40 over is in the cards.
So know having found a well represented shop to do the work, we're sourcing parts.
Pistons are at the top of the list.
Availability is proving difficult.
The Wiseco piston is the target at this point.

Now I'll throw a spanner in the works here and see what your educated minds come up with.
This engine will be carbureted.
Do you think with the often excessive fuel wash that comes from a carb, and it does happen particularly on cold starts, is going to kill those 1mm rings?
And to add to the debate, as it's been touched on here already, what is a half a millimetre in the difference going to provide?
1/16th (1.5 mm) vs 1 mm.

No. Thin rings last LONGER. Tune up your carb. And .020 makes a difference. A 1/16 inch is .0625 so a .020 change is almost 20%.

I watched the Hidden Horsepower podcast with Larry Morgan. You should go watch it. He will tell you how much longer thin rings live. And you’ll also hear him tell you how he could have been 10 years ahead of everyone, but fear held him back.

Me? I’d wait on pistons and get something worth having. Rushing through a build is what a broke assed teenager does. Delayed gratification is real. There is price and there is value and they are different. One is far more important that the other.

I hear what you're saying. I've had this project on the shelf pushing better than three years now. I can wait a little longer.
I've subscribed to Morgan's channel. I'll look for that vid.
Thanks.

As for tuning the carb, it was pretty tight as it was but cold starts are still a killer.

[skinny z]

Yes PRH, the big question is , how far down the road is he on his engine build ? Mark H.

yes again & again & after so many machinations ... when will actual assembly begin ? when ???

Easy there big guy. When COVID and the economy wipes out 30% of your income over the course of a couple of years, these hobbies take a back seat.
But, I'd like to think I'm back. Disassembly is complete. Machine shop on deck. Now the parts parade begines.
By the way, I thrive on machinations.
Thanks for waiting...

[skinny z]

Does anybody know of a 40 over, forged, flat top, 1.560" compression height piston with 1 mm rings that's actually in stock somewhere?
I'm having a hard enough time with the 1/16th (1.5mm) versions.
I may be waiting until June or beyond.

[skinny z]

Piston List 357

4.040, 1.560 CH, 3.48 stroke, 5.7 rod, 1/16, 3/16 ring pack, forged flat top.

Wiseco PTS503A4 - Wiseco Pro Tru Street Pistons

Mahle Powerpak pistons 930200040

Sportsman Racing Products 138082 - SRP Small Block Chevy 350/400 Flat-Top Pistons

DSS Racing 8100-4040 - D.S.S. SX-Series Forged Pistons

DSS Racing 1-2000-4040 - D.S.S. FX-Series Forged 4032 Alloy Pistons

Speed Pro H100CP 40 - Speed-Pro Hypereutectic Pistons

[NewbVetteGuy]

Does anybody know of a 40 over, forged, flat top, 1.560" compression height piston with 1 mm rings that's actually in stock somewhere?
I'm having a hard enough time with the 1/16th (1.5mm) versions.
I may be waiting until June or beyond.

The Mahle PowerPak piston PN you listed in your previous post is in stock for $648 here: https://rcagarage.com/shop/engine-compo ... c1bd7ba386
The Honey price-checking browser plug-in says that RCAGarage has the cheapest published price for regular retail folks.

Speedway and PitStopUSA have a little stock on that PN, too but they're a good $100 more.


Adam