Oh man, you are really going to upset 1967dartgt now!

Ok man, please explain how you will pull the piston down further but not push it up further in the cylinder.

The first part of the equation is to determine DIAMETER.
The part that is being ignored is RADIUS.

Did you even read any of the posts before you jumped on board with Brett's point of view? See attachment!
Here is something for ya, I'll send you guys a cheap cast eagle 4.000 stroke SB crank, if you can regrind it to 1.850 journals and 4.500 stroke (without welding) I'll give you 10 grand, if you can't I get your 67 Dart? Let me know if you're in and I'll have a law firm draft up the contact.

As I stated all along, the MAX stroke can change is the difference that the journal diameters change. And it just so happens to be twice the OFFSET. Realizing that the change in journal diameter and offset are different values is the most misunderstood area for some reason

I stand corrected.

Doubling the offset is the max that stroke can be increased, this is unarguably 100% correct!
However, there is a difference between change in journal diameter and offset.

Pretty sure the diagram I made and posted shows exactly how it works, and It's not my theory but actually bound by the laws of mathematics. But sure I'll take a read on your posted article.

Taken directly from the second paragraph in that artice:

"In theory, going from a 2.10 to a 2.00 journal should allow a 0.100-inch stroke increase if the throw is reground with the max possible offset (relocating its centerline by 0.050 inch)"

What can you not wrap your head around?

Holy crap, this is basic math and as simple as understanding camshaft events...wow.

But id ask the OP, why build a motor around a set of connecting rods?

Ive had plenty of those rods from nascrap purchases and they pull maybe $100 a set on ebay.

Better yet, why do so many fall for the "dyno only" parts thinking they are not abused.

[quote=1967dartgt

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. [/quote]

I don't know if all the bad info reduces post counts, but bad info like some in this post is the reason I spec and build my own engines.

Here is the problem with bad info on the internet. Certain types of people:
Fan boys
Nutswingers
Followers
or people who refuse to think for themselves have the view that certain individuals that they look up to are not capable of being wrong from time to time, so they jump on board with whatever they have say and go forward repeating the bad info as if it were the gospel. If someone stops posting here because they cannot accept their views being challenged, well I guess that makes them weak. I encourage independent thinking and for everyone to form their own view and accept that EVERYONE is wrong on occasion.

Years ago one of the brothers, Gary, from ABS and Speedomotive CO family shared some information he got when he was invited to attend Daytona Speed week and given several tours of the better NASCAR teams shops, this was over twenty years ago so keep that in mind for the rest of this post.
One of those teams had seven different engine dynos, three Super Flows, three DTS and one Studka hybrid, running 24 Hrs. a day seven days a week on engine development
That had the software to replicate the entire race at Wadkins Glenn or the other road course they use to race at in New England Straight ways, all the corners, acceleration and deaccelleration (CRS )
My point is some dyno parts are tested and ran a lot longer than some raced parts are to find the actual time limit under simulated race conditions before failure
If your going to use race parts for racing buy them new

The rods are new and my current engine needs a rebuild. My cam went flat again. This was the second one that it has done so. Will be going to a roller this time. just trying to use some of what I have available. Some people do it quite often.

I don't believe we have to go through this every two years.

On any crankshaft the stroke is the distance from the CENTERLINE of the main journal to the CENTERLINE of the rod journal, times 2. When we decrease the diameter of the crankpin b offset grinding, we move the centerline of the crankpin or rod journal by 1/2 the change in diameter. That's because the centerline only moves half of the distance the innermost part of the journal does. Then we multiply it by 2,as in my initial equation.

So the maximum perfect world increase in stroke is equal to the change in crankpin diameter.

It isn't a perfect world and to get a perfectly round journal using real tooling, the outermost bit of the rod journal has to be ground if only a little. So on Earth, anyway, the increase in stroke will always be slightly less than the change in diameters.

IMHO the steel that goes in a NASCAR rod is at the top end of 4340 quality. So even if it has run 500 miles, and is down to its 57% fatigue limit, if it magnafluxes OK and if the journal and pin bores are round, I won't be able to break it at 5500rpm.

R.