Flathead Crank Knife Edging....pro's & con's

Lightening innards will allow faster acceleration at any speed (except maybe at launch when the inertia helps get the thing moving...), decreasing oil drag will help in proportion to engine speed, I'd think.

 

The process that Mike Bishop uses to remove stresses from a crank, is what results in a polished finish. The fact that it "looks pretty" was just an after effect.

This subject - removing "stress risers" - has been "kicked around for a long time.

A Teflon coating on a crank, doesn't contribute ANYTHING to reducing stresses in a Ford/Merc flat head crank.

But if your looking for the last "poofteenth" - a "carps" phrase - of performance; who is to say it won't help??

If the NASCAR boys use it; someone must be right.

 

Hey Bluto,

My crank ended up being porus as hell when I pollished it. It had oil seeping out of multiple locations... Would that pose a problem for teflon coating?

As for pros/cons of 'knife edging"...

I can't think of a con unless you slip with the grinder and junk your crank....

I polished my Flathead crank to lighten it slightly, remove stress risers, and make it look better... It's a street motor... I just like personalizing things.

I took it as far as I felt was reasonable for the application, for my attention span, and my sanity. You should do the same...

I believe it makes the crank more impervious to destruction, and might shave off some rotating weight. I know there had to be a few pounds of metal on the floor after I was done (I left it there during the job to see how much I ended up with). That alone might be enough for you...

It was a lot of work and time. Every engine is different. You will have to decide for yourself how far you want to take ANY modifications. Once you decide that, it won't really matter "how much improvement" you get out of any one modification.

Even in a race car, I doubt you'd be able to tell that "Knife-Edging" alone made a difference between 1st and 2nd. But in those cases you're spending a lot of money and time on every little detail so adding Knife edgine to your to-do list probably wouldn't make much difference to you. So why not just do it?

If you're a perfectionist, how perfect does it have to be?

 

here is the link to av8`s mike`s crank , if it work`s?
or search, bottom end flathead questions

 

Killer post!
Hi Bluto!

 

Joe:

Let me know how you make out on this subject. Should be doing my crank this winter (fingers crossed).

Next time you are going to Flatdog's mind if I tag along?

Good luck.

 

Kilroy Get a new crank! Sorry Telon won't seal the crank from much internal oil pressure

Guys.... Stress relieving it done by having the crank shot peened At least three sizes of shot. This doesn't remove any metal. AND they have to get into the radii

I had an old friend that did all Dupont's Teflon automotive application research. He taught me a bunch over the years. He first started with this:

''This of two blocks of ice. They are rough but slide easily between each other"

Don't use an ''Automotive Racing Coater" find an industrial guy that's a car freak. He'll do a better job cheaper and your crank will be the only one in his shop.

 

We did not knife edge ours - but we built it 15 years ago before flatheads (and over-the-counter) speed equipment was so available. It is 296 cubes and very responsive!! The crank was from Speed-O-Motive. I think some of the people who were at BTT50's can attest to how it sounds!

 

Checked out knife-edging in the Vizard book...Chrysler engineering sourced info was 4HP @ 7500 RPM on small block engine...prorated to flathead RPM and output, that would probably be way below any measurable change...
interesting stuff in there--a couple of different leading edge treatments show same results, book says square as-is trailing edge sheds the oil best...
LOTS more in the book on detailed prep, coatings, etc.
All this stuff starts showing results at very high R's.

 

Kilroy

Nothing will help a STOCK crank......perhaps prayer Sorry I just have never been that religious

My comments are really directed at after market cranks

I forget that some here are trying to get HP outta stock stuff

 

Any weight reduction to a crank means more of the power developed is available to the driveshaft. The most important weight is at the outer edge, so reducing the OD, chamfer, knife edge etc. all have an effect.
Reaons not to do this: requires higher RPM for stable idle, increased strain on starter motor, more delicate clutch (or higher stall) required for stop-n-go.
Torque reduction? Doesn't exist.
A knife edge also reduces the cross-sectional area of the counterweight so windage is also reduced.