Is there any truth the M8 cranks are more stout compared to its predecessor?
What about measure runout when you change cams, still way high?

 

Ask a builder that deals with them every day.
Most here have never taken the deep end apart as it is wat too specialized,

 

Spoke with my Indy a couple months back, (one of the biggest in the country) as far as strength goes he says they are about the same, most all of them are measuring in at .006 ...

 

 

You mention two unrelated things there! Runout of around .006 is presumably in spec (I don't have an M8) and doesn't affect strength.

 

While the pinion shaft and output shaft are the same size between TCs and M8s, HD upped the crank pin diameter some so they should be stronger. Runout does not equate to strength.

 

Until someone actually tests these cranks, or does an A-B side by side load stress test "should be", "could be", "might be", or "I think they should be" are worthless comments.
OP-
Neither pin diameter nor run-out measurement in and of themselves equals strength, reliability or longevity.
There has not been a side by side comparison so to answer your question......no one on this site knows-period.

 

Well SnS made a 1 1/2 inch pin cranks as their first attempt to make TC cranks and it sucked. I've killed 2 and have a rebuilt 3rd that is about to die. Their 3 piece 1.671 crank-pin cranks seems to do much better. At least we know going smaller don't work. Maybe a little engineering logic helps.

 

I have blown up and destroyed all kinds of cranks, and thats on me, and not on the manufacturer...
It is common knowledge you have bagged on S&S cranks in the past, but when I asked "what crank brand is better", I get crickets........
Here we go again...
"seems to do much better"...
Have you or anyone done AB testing to prove this? How? What testing proves this? You super limited shade tree mechanic experience on a couple cranks? Any engineering logic knows that is a laughable statement.
Do you realize S&S prostock cranks that hold 300 plus HP are only 1.5? ( I have run them BTW, but once again you haven't, nor do you have any data to support your claim). https://www.bikernet.com/pages/SS_Ho...h_Engines.aspx
Could it possibly be the reengineering of the entire crank assembly, and not the crank pin size in and of itself as I said?
I have also taken their TC cranks that "sucked" as you said, for over a decade and make alot more HP and beat on them much more than your builds.
Hmmmm.....
Again (this gets old), unless you actually test them (like when you did a great job actually testing the various carbs available-straight up, side by side for flow), you simply don't know.
What if someone said "a Mik 48 should flow more than a bored G".....I say, BS, unless you test, you don't know.
I agree, bigger usually is better, but prove it or don't say that crank pin size, in and of itself, makes a superior crank.
Prove it.

 

We've been steadily building M8's here, and as of now, no crank issues have been witnessed, including 3, 124"s.
Scott