Mysterious stroke/ crankshaft

[jeff1234]

I'm working with a friend on a common block. It is a standard bore with P566 pistons,TRW or Sterling or whomever. We thought we were working on a 2.2 or a 2.5. When I measured the stroke from deck to piston top at the edge of the piston nearest the cylinder wall I came up with 3.691. That doesn't meet either the 2.2 or 2.5 stroke measurement.
Is it possible this engine has a 2.6 crank in it with some other connecting rod? Yet even the 2.6 stroke is 3.86. This is weird.
Anybody have an explanation?

[jpcturbo]

Doesn't a 2.2 have a stroke of 3.622" and the 2.5 has a stroke of 4.090". http://minimopar.knizefamily.net/enginehistory.html My money is on that you have a 2.2L crank in it.

[jeff1234]

.070 difference between a 2.2 stroke at 3.622 and my measurement of 3.691 of the stroke measured is alot to account for, so i disagree. Perhaps someone else might have more info.

[cordes]

.070 difference between a 2.2 stroke at 3.622 and my measurement of 3.691 of the stroke measured is alot to account for, so i disagree. Perhaps someone else might have more info.

How are you measuring the stroke? I would think the piston rocking in the bore could account for a least little of that depending on the rings, etc.

[jeff1234]

I used a dial calipers. I rotated the crank to align the flywheel mark for #1 with the zero mark on the timing window which required a couple of back and forth movements. I had previously noted that the piston was resistant to being rocked. I measured #2 on the back side of the cylinder by extending the depth probe to the point that would allow downward pressure on the dial to make the measurement. I held the probe against the cylinder wall and squared the tool itself against the deck. Its unclear whether the piston was perfectly centered.
I can account for .010 between the piston top and the deck and maybe .004 in the rod bearing and wrist pin clearance, so that takes the difference down to .057, that's probably in the realm of piston rock, so it sorta looks like Jeff is correct. It's a 3.622 crank.
Out of curiosity I found that if the 2.6 crank would work in a common block that the rod journals of that crank could be reduced by .118 inch and the stock con rods could be used but I didnt know the 2.6 rod length. The difference in stroke would need to be addressed.
The reason I wondered about the 2.6 is that this Rampage had changes that led us to think that maybe the previous owners were trying out different things like four wheel disks, removing the fuel filler door and changing tank location etc. Like maybe a drag car.

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By the way, I had to retype this twice because even though I was logged in, when I tried to post quick reply it popped up a message saying that I wasn't logged in. Ultimately i retyped and copied then pasted after getting back to the page. This needs attention.