Doc's article below mentions stroking via offset grinding the crank and with a 3.5 bore piston and achieving a 240CID slant 6.

https://slantsix.org/articles/stroking/stroking.htm

If such is an option now a days (offset grinding)?

Would these pistons work: https://www.summitracing.com/parts/uem- ... 0#overview
As far as I can tell the compression distance is 0.10 shorter than the stock slant 6 piston

Or does anyone know of a 3.5" bore piston for a stock build?

Jase I like your thoughts.
Custom pistons can be made. you will be spending a lot to get this built.
I have a grinder in Dallas and I will be taking a couple cranks early next year.
I will ask him.

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Hyper_pak

The amount you can offset grind is small will only gain you a couple cubic inches. The .100 over pistons get you to 238 cu in.

The pistons you list have the wrong size wrist pin.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Agreed that the offset grind does not gain much... so maybe it is not worth the effort.. which then probably takes these pistons out of the running.. as they have a slightly short compression height..

And then dealing with finding a bushing that would allow those pistons to be used is also not worth the effort... I am seeking for options for something that does not require custom pistons and I thought with the above ones with an offset grind, might work....

Offset grind will work fine with stock comp ht pistons. You can likely still get 0.060"-under or at least 0.050"-under rod bearings from King, which if you have a stock crank in good shape you can get about 0.040" or maybe up to 0.055" extra stroke. 0.040" gives 2.3 extra cubes with a 3.46" bore. My local crank grinder did a mild one like this (0.0075" offset grind for 0.015" extra stroke) for a minimal or no extra charge about 10 yrs ago. We used 0.030" bearings because I had them laying around. You will lose nothing in terms of durability. It will raise your comp height (piston to deck) by 1/2 the gain in stroke. That gets you more compression too with less milling. It's a win-win-win, for most NA buildups.

Now that I've typed this out, I should get more of my cranks offset ground. Time to buy some bearings...

Lou

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Home of Slant6-powered fun machines since 1988

Yes Lou, you need more projects!

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Hyper_pak

If someone just could make a custom undersize bearing of say .150" 0r so them you could offset grind a larger amount and pick up some cubic inches and compression even using stock pistons. Anyone know someone at King??

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Interesting idea, Rick. That would probably work well. The other way would be to use a rod with a smaller journal and offset grind away. Would need to match the pin width, which wouldn't likely work with the forged crank (bearings wider than just about anything), but likely you could find a match with the cast crank.

Lou

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Home of Slant6-powered fun machines since 1988

My "smaller journal rod" idea will likely not work either. Almost no engines have a stroke and rod as long as the 225, so finding a small journal with a 6.6-7" rod would be tough.

Here are the 0.060"-under rod bearings for the cast crank engine: KGB-CR6615AM060
0.040"-under for the forged crank engine: KGB-CR614AM040 (put 60 at the end for the 0.060"-under version - not listed)

They are special order and I think King waits to have enough to make a run. I have a set or two of these, but it's been a while since I've ordered them.

I wonder if we called them and asked for a really big undersize (0.100"-0.150") and wanted 20 sets they might do it??

Lou

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Home of Slant6-powered fun machines since 1988

Can't hurt to ask?

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

The 5.4 Ford modular engine appears to have a 6.657" rod, with a width on the big end at .937. that is too narrow for my forged crank engine? https://www.summitracing.com/parts/esp- ... d#overview

Interesting! Won't work with forged crank, but might with cast crank. Need to look up big end width.

Lou

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Home of Slant6-powered fun machines since 1988