Good evening. I'm looking for cast pistons for my "170 Stroker" build. I'd prefer a hypereutectic set, but "regular" cast pistons would be fine. There are approximately twenty-eight million posts about pistons here, and I've spent several hours poring over many of them, but I'm still adrift. Can you help me identify some options?

Here's what I've got so far:
- 2843169 head
- 3.64" stroke (198 crank)
- 5.71" rod (170 rods)
- 9.68" deck height (170 block)
- The motor will be naturally aspirated.

Here's what I'm aiming for:
- finished bore diameter anywhere between 3.46" and 3.48" (This leaves some room for another rebuild.)
- compression ratio in the neighborhood of 9.5:1 (Head and block will be resurfaced as needed.)

Bear with the newbie, here: If the 170 crank has a stroke of 3.12", and the pistons in a bone-stock 170 (with a 1.765" wrist-pin height) are flush with the deck at TDC, then swapping in the 198 crank would pop them out by 0.26", right? Am I looking for a piston with a wrist-pin height in the neighborhood of 1.5", give or take whatever the desired compression ratio requires, and whatever I can do with resurfacing the head and deck?

I saw Matt Cramer's informative post about Japanese pistons (http://www.slantsix.org/forum/viewtopic.php?t=5073); maybe one of those would do the trick. Forged would be a bonus, I guess. I have no idea what my final combustion chamber volume will be, and I don't know if my pistons will need to be flat, dished, or domed.

Heyyy... Silv-O-Lite Cast Pistons 1461-1-0MM measure 88mm across. They have a wrist-pin height of 1.438", and the pin diameter is 22.0mm. Could they work?

https://www.summitracing.com/parts/uem-1461-1-0mm

Really...for anyone doing the kind of work you are getting into....pick up the phone, call JE or Wiseco or whomever and order a set made to your specs. Lay off the beef jerky/Starbucks/cigs/Astroglide/Chikc-FIl-A for a year and it'll pay for it.

Custom engine combinations should first be worked-out, on paper, in detail. (your "plan")

Measure your current head's combustion chamber so you know it's starting volume.
A camshaft decision will have to be added to the list of info. for the plan. (know your planned intake valve closing point)
Double check the current deck height or better yet, swap-in the 198 crankshaft as a "mock-up" and measure how far the piston(s) sticks-up above the deck.
From there you calculate the ideal piston deck height, then check if anything "off the shelf" is close to that.
If not, you have all the info. needed to order a custom made set of pistons that will work exactly to plan.
Note: 22mm P. Pin = .866 and the 170 con rods are at .901 (22.88mm)
The Silvolite 1290H or 1291H are a couple of off-the-shelf pistons that could be made to work.

Take actual measurements and Write-out A Detailed Plan, On Paper!
DD

https://uempistons.com/series-2112-silv ... 1290h.html

That's what I'm trying to do; I fell down on the "measure first, ask later" part. I will ask my machinist to mock up the engine and take measurements.Thank you. They're hypereutectic! Bonus.

That would definitely yield the best results, but part of the appeal is building something interesting with stock and off-the-shelf parts. I might just be telling myself that because I expect fearsome invoices from the engine shop, and I'm trying to save on parts.But... these essentials you've listed... Who can live without the occasional romantic dinner, indoor sports, and afterglow smokes?

Stay the course, my good man! lol

Last year I made measurements on a 170 block with 198 crank and stock 170 rods and pistons. The pistons stick way out at TDC. Based on the measured distance out, I ordered a set of Silvolite pistons for a GM 3.1L V6 with 1.45" comp ht, 3.505" bore, and an 11 cc dish. Part number 1486HC. I believe Summit still has them and the rings and they are not expensive. They look nice and have skirt coatings. With my particular parts, this should give 0.050" in the hole at TDC. I do not know if this block has been cut, and I intend to clean it up 0.010 or 0.020" as needed.

Plan is to put a head on it that I will have cut appropriately for 8.5:1 (or so) comp, and run 15 psi boost into it... Not sure which car yet. Might be a year out for me?

Hope this helps,

Lou

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Home of Slant6-powered fun machines since 1988

It does - thanks! Looks like my (very rough) ~1.5" wrist-pin height estimate is OK, and I'm getting more comfortable with designing and building for a target compression ratio.

Hey Lou, I know this is a little late, do you remember if the pistons you bought for this build were flat tops?
And I will be able to find the thread now.
Stan

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Hyper_pak

Hey Stan,

Doesn’t the 11 cc dish mean it is not a flat top? I’m not sure.

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Rob

I’m Mater
The Kentucky Poser

The silv-o-lite catalog shows 5 pistons at 1.5 and one at 1.8, this is at 3.5 bore.

I'd go the 3.5 bore to start with. If you kill a hole just sleeve it.

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Official Cookie and Mater Tormentor.

The part number brings up everything in their catalog, Stan (1486HC). Dish is 0.095" depth and 2.95" diameter, or right around 11.7 cc by my calcs. See post right before your question...

Lou

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Home of Slant6-powered fun machines since 1988

Duh....
Thanks Lou and others.

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Hyper_pak