first I am going to say I'm not really sure stroker is the right word. This line of thought started due to the recent 198 and big bore threads. I am not sure how I actually ended up with this line of thought, but here goes...

Assuming the 170 block can be bored to the same 3.504 bore as the 225 it would be able to use the 89mm pistons. The problem would be finding a piston with that bore and the correct height. In the 225 the long 198 rods are used with the shorter big bore pistons, there aren't any slightly longer rods available for the 170.

The specs I found online for the 170 rod are 5.707 (145mm) long, crank journal (stock) 2.187, and width at crankshaft of 1.21 attached to a piston with a height of 1.625 or 1.765(I've seen both numbers). The 1.765 was in an old post from Doc so I would trust it more.

I don't know if these specs are accurate and I don't feel like tearing apart my spare 170 to check at the moment. I found a rod with piston combo that looks like it will fit the crank with .020ish machined on the rod journal. The pistons are flat tops with 4 valve reliefs.

The cheaply available in every US junkyard rod/piston combo is:

Rod length 158.5mm (6.24") length, big end width is 15mm (measured a bearing shell, not the rod), designed to fit a crank with a stock journal of 2.1644-2.1654

Piston spec 89mm (3.504) bore with 30mm (1.18") piston height.

My math puts the stock assemble length of the 170 piston/rod at 7.332 (or 7.472). The junkyard assembly would be an assembled length of 7.421 (188.5mm)

I don't know if this combo would work. The problems I see are the narrow rod bearing .6 inches wide on a 1.2 inch journal. Another issue is the (maybe) slightly longer total length and boring the engine to max bore. The pistons likely could have a bit shaved off the top since they have valve reliefs that can go away if needed.

The donor engine to source the rod AND piston assembly is the Honda J35 v6 put into every honda odyssey, pilot, ridgeline, and some accords/crosstours since 1999. Those engines are everywhere(in US). I have pulled pistons out of the engines at 200k+ with minimal side scuffing (teflon skirts) and good rings. These engines are prone to oil rings getting stuck in carbon, but the compression rings don't wear out. I will get my hands on the next v6 we swap out for the core charge to do some in person measurements and maybe make a coffee table out of it.

edit: A weird advantage to using a honda rod is that if you know how to use "select fit" bearings you can get your rod bearing clearances perfectly exact. Select fit is a hard concept to explain and I would have to refresh myself before I could explain it properly.

Good thinking in most aspects, but you need a rod width that will match the crank journal width. Otherwise, the rod will wander around fore and aft, and will get destroyed quickly. Almost NO gasoline engines will have rods this wide. I have not seen any. You are probably looking at a custom rod. I also would not call this a stroker, since that would require a crank with a different stroke and has nothing to do with the rods and pistons.

1.74" is the spec I have in my head for stock compression height for all passenger car 170, 198, and 225 pistons. A few other heights around that number (lower or higher) have been or are being produced for industrial or mildly different aftermarket applications.

I'd say get the stock 170 rods bushed on the small end to accept your favorite piston, chosen by the method you are using. I have picked/used pistons using this method of mixing and matching, as have many others.

Lou

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Home of Slant6-powered fun machines since 1988

Just a stupid question BUT what would happen if the machinist only machined the center of the crank journal to the smaller bearing size. If only the center of the journal was smaller it would leave a step and center the bearing. I don't know if this would cause side forces on the bearing shell itself or if it would just be perfectly fine.

You would need to machine the step deep enough (and find a suitable rod) so that the wall/step rides on the side of the rod big end body, not just on the bearing shell. I cannot imagine the shell would center it properly/solidly, or let oil out properly.

I believe Mike Jeffrey and others may have used a small Honda rod journal and machined a step, but the diam of the big end was very different than the Slant 6 rod such that the rod body rode on and was centered by the step. You could also get the crank welded up and machined to give a journal to fit the narrow rod. Probably $1000 these days for such mods? You could then choose what stroke you want too.

Lou

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Home of Slant6-powered fun machines since 1988

lol and it leaves the realm of cheap/easy. I figured this line of thought would end this way. I have so many projects ahead of old car tinkering it gives me something to think about.

If you spend 15-30 minutes on 2-3 days a week doing car tinkering, you can get a lot done...

Lou

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Home of Slant6-powered fun machines since 1988

The shed(24'X32') I built that houses the car needs a 150ft of power cable to even see out there. I did have a 100ft cord from the garage but the garage is an underpowered circuit already. Days are dark before I get off work. Snow and ice outside so the shed is also cold, makes me less eager to work.

My current things before valiant.

Finish remodel of living room, found water damage with no leakage in vaulted ceiling. Roofers were going to come in and patch that section this week, snowstorm and ice have delayed. I have ceiling drywall and insulation and walls to reinstall. Since it is now a COLD room in the room it comes first. Moving blanket door curtains for the win in this one.

Next will be a redoing the property power feed to 200 amp service with a feed line to the mentioned shed. Somewhere in there I need to build the staircase into the loft (20'X20') of the shed to move all the stuff packed around the car and various other items in the garage next to the house.

So I have a few really big elephants that all need some bites taken out of them and my valiant just sits waiting.

Fair enough...

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Home of Slant6-powered fun machines since 1988