Ring Pack Thickness: Question

[skinny z]

Just throwing this out there but would it make any sense to have +.030, in-stock pistons abradable coated and forgo the +.040 deal all together?

Looking at the bores and I'd say it's going to take the full .005" per side to clean up. Coatings are great although I'm not sure if this would even be a possibility. Admittedly, it's something I've never looked in to.

[skinny z]

FTR:

IMG_20220115_114849607.jpg

IMG_20220115_114914613.jpg

[rfoll]

$420.99 for a hyper piston?

Which?

https://www.summitracing.com/parts/slp-h100cp40

[skinny z]

$529 CDN funds.
Seems having a thin ring puts a premium on a Sealed Power piston.
And not in stock ...

[rfoll]

How much money are you willing to spend to get a few MPG and HP. How long at your current driving habits will it take to recoup your expenditures. $648.99 for pistons on a street car? Plus about $150 or more fore rings?

How much less performance/longevity are you willing to settle for may be a different way to look at it.

I would surely like to see more than the 5 hp quoted elsewhere in this discussion. We are after all talking about a 350 with a factory cast crank. One of the things no one has mentioned is the likelihood of finding enough room for the overbore to use forged pistons. They tend to be .002"-.003" smaller in diameter.

[skinny z]

Factory forged crank.

As for piston clearance, anything I'm looking at is a 4032 alloy. Low expansion as it's described when compared to the 2618.
15% in the difference according to JE.

[ClassAct]

Just throwing this out there but would it make any sense to have +.030, in-stock pistons abradable coated and forgo the +.040 deal all together?

Looking at the bores and I'd say it's going to take the full .005" per side to clean up. Coatings are great although I'm not sure if this would even be a possibility. Admittedly, it's something I've never looked in to.

I thought about the .030 piston and a coating but I’m not sure if .005 per side makes a difference on ring seal.

Line2Line coatings has an abradable coating that will go up to .010 per side (.020 total) that is designed to do what we are discussing. It is designed to get the piston to run at zero clearance. I’m considering sending my pistons out just because the idea makes sense in my head.

I would call Line2Line and explain to them what you are doing and ask if that has potential.

I’m know for sure I’m going to have my oil pump coated.

[skinny z]

While I can see the merit in coatings in general seeing as we do our own in house zinc and manganese phosphating, I can't see these bores being round enough for anything other than the next oversize.

[BobbyB]

While I can see the merit in coatings in general seeing as we do our own in house zinc and manganese phosphating, I can't see these bores being round enough for anything other than the next oversize.

Have you measured the bores?

[skinny z]

That'll be this week.
But experience tells me they're toast.
The hope is that there's enough material to go only to .040" over. Might be worse. More than a couple of bores are deeply scratched.

[rfoll]

Factory forged crank.

As for piston clearance, anything I'm looking at is a 4032 alloy. Low expansion as it's described when compared to the 2618.
15% in the difference according to JE.

They are still smaller. You won't know how much until you have them in your hands. Curiously, the later model GM pistons such as the Vortec motor uses are .001" smaller than the previous ugly dished pistons.

[skinny z]

Any and all measuring I do is going to be duplicated by the shop. Which is how it should be. I'm measuring more for knowing than anything else. I'm curious as to how wiped out these bores really are.
IIRC, that engine had a couple of intense overheating moments when the temp sensor in the cylinder head crapped out and disabled my fans.
There's that and also the few times I was forced to start it at freezing temps. Lots of fuel wash in those few minutes it takes to warm up and idle.
Anyway, I'll soon know but my best educated guess is 40 over.

But further to this thread, and all of the replies and direction, it will be thin ring pack. Seems a no brainer.
The rest has yet to shake out.

[Dan Timberlake]

[/quote]
I would surely like to see more than the 5 hp quoted elsewhere in this discussion. We are after all talking about a 350 with a factory cast crank. One of the things no one has mentioned is the likelihood of finding enough room for the overbore to use forged pistons. They tend to be .002"-.003" smaller in diameter.
[/quote]

A few decades back I think off the shelf pistons were made for the nominal bore, and had the clearance built in.
Thus the bore needed to be 4.040" for the various flavors of cast or forged pistons.

[skinny z]

That was my recollection as well.
Fast forward a few decades to today and I can't say for certain how it all measures up.

[allencr267]

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.