Standard SB rod journal to a 1.85 Honda journal. By offset grinding the crank. How much additional stroke can you gain? I'm figuring about .150. Does that sound about right? Jim

You'll get maybe .125 if you can take it that far.

SB LJ to Honda 1.888 journal: 2.1 - 1.888 = 0.212 -> 4.212 theoretically minus some margin for the grinding. Say 4.205" maximum offset.

Or, if Mopar SB journal 2.125 similarly 2.125 - 1.888 = 0.237, -> 4.237 max/4.23+ ....

4.25" cranks are readily available.

I know but I have a set of Pankle rods with the smaller journal. I would like to use by just turning the crank I have.

You can.. just talk with your crank grinder for the clearance
needed.. smaller dia will use less

2.125"? Or 2.100"?
So 2.125" down to 1.850" = .275" you can not get it all but .250" should clean up back to round.
So your stroke gain would be .500".
4.500" stroke but 1.85 on 4" crank will have no Journal overlap.
Anything you offset will be 2 times the stroke gain. So .050" offset will give you .100" gain in stroke.

Those NASCAR rods are the siren luring you onto the rocks. The Honda journal, though, is 1.889" The Mitsubishi journal is 1.850"

Hughes' stroker was such an animal, a few years ago, except it used the Honda journal. 4.180 stroke.

R.

Man, I wish mine would have worked like that. When I did my crank from a 2.125 to 2.00 I only gained .125 and only ended up with a 3.91 stroke What did I do wrong??

Did nothing wrong! Lots of WRONG info in this thread. Change in journal size is the max you can gain by offset grinding!
2.125-1.850=.275 MAX added stroke theoretically
.250 is realistic

Yes I know, I was just trying to throw a little levity into the discussion. The offset = stroke increase was the way it worked when I took plane geometry 70 years ago.

Dude you should check your facts....

Will not argue with you I offset cranks all the time.
You double What you offset period

It changes the center line of the Journal in relation to the mains.

And it turns in a circle so it doubles what ever is offset ground.

You sure about that Brett!! You only just offset the crank in the 981hp small block you built.

Man lots of bad info in this thread. You have a engine builder correct you and you tell him he is wrong, wow. Wonder why so many people stopped posting in here.

visualize a 1" circle inside a 2" circle. there is 1/2" of space vertical above it and 1/2 of space underneath it. If you moved the circle to the bottom it would move 1/2" (minus a bit for cleanup to get it back to concentric), this is the "throw" increase (1/2"). doubling that would be the stroke increase (1") cuz it would push the piston 1/2" higher at TDC and 1/2" lower at BDC then where it was before. EDIT for a slight stroke increase with all Mopar stuff to finalize quench for instance, CNC motorsports has 50 under SB rod bearings & eBay has some 40 under

It depends on the crankshaft and its oil passages, I have several older forged top fuel cranks with Mopar rod journal sizes, one KB that is 4.500 stroke and according to the crankshaft shop I sent it to it can't be offset ground and destroked due to the oil passages or something else I can't remember now I sent them a another older forged Bryant 4.250 stroke top fuel crank with stock Mopar BB rod journal sizes with one spun rod bearing journal and they offset ground it down to 2.200 and 4.375 stroke with no issues
Check twice before deciding

Brett, no doubt you can build a great engine, and are an absolute master with cylinder heads, but you can't math.