crank swap

foreverfaster

Premium User
Let's make sure i do this right.

So i'm putting the girls away for the winter,.. nice shelf in the basement dedicated to motor storage.

I've had this flat head for a year or so just setting in the shop.. was told was a great motor.. ya ok,... i had not used it because the fly wheel key way and the crank key way were both wasted...
i found a donor motor and started swapping the crank out.. the replacement crank from the motor that didn't have a bearing..
after measuring everything looks like it will all swap nicely, anyway.

heated up the bearing with a heat gun and pulled it off with a pulley puller..
the junk crank coming out clearly had a lot of work done to it.. machine work and polishing.. NOTE the gear on the crank was fixed unlike the donor crank. which is key'd.. like an animal.

nice alum rod and good arp bolts. As i fit everything back together. i set the bearing on a heater for a couple of minutes and slid right on with no issues.. poured oil over it to cool it down faster.


Monday i'll see about getting a side cover gasket.. SO the big question is am i doing this all right.. no i didn't rebuild the whole thing.. just measured and swapped the crank.
Will any flat head fly wheel fit this??
How do i figure out if i need an offset key for the crank and flywheel?

Thanks
 

flattop1

Dawg 89
seems to be right.
most times you polish the crank for a slip fit on the bearing.
was the pork chop/balance weight of crank ground down ?
Usually about 1 1/2 inches long and 3 /16 deep for cam clearance , if over stock lift.
if so you may want to match that.
most any flywheel will work, flathead of course.
search in the hole timing, you will want to be around .280 or use degree wheel.
 

CarlsonMotorsports

Premium User
If the crank that you pulled out had machining and polishing done, it is not stock class legal (at least the machining part.)
Always slip fit the bearings on the crank so that they "float." These blocks are align-bored to the crank (not the deck) so you may be "undoing" some of that work by fixing the bearing tight. Also, if the sidecover is being changed out for another, that will also affect the alignment of the bore.



-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
28 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 

foreverfaster

Premium User
If the crank that you pulled out had machining and polishing done, it is not stock class legal (at least the machining part.)
Always slip fit the bearings on the crank so that they "float." These blocks are align-bored to the crank (not the deck) so you may be "undoing" some of that work by fixing the bearing tight. Also, if the sidecover is being changed out for another, that will also affect the alignment of the bore.



-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
28 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Just changing the crank and then getting a replacement flywheel.. is there a way to post pics on here?? i could post a pic of the crank i pulled.
 

foreverfaster

Premium User
I honed out the bearing so it is more of a slip fit and installed .014 gasket. I'm not getting any side to side play on the crank. would it be acceptable to put another 0.14 gasket ?
OH, and i noticed the cam did not have a compression release... does this mean i'll have a tough time pull starting it?
 

flattop1

Dawg 89
Brian is 100% right no polishing , lightning or grinding Allowed. Stock class Racing.
Use which ever gaskets work out.
Compession release is not like a clone. It's ground into the cam.
 

CarlsonMotorsports

Premium User
The compression release will look like a short flat spot on the IN valve close side of the cam lobe. For WKA it must have a minimum of 30* duration. Up to 3 sidecover gaskets are permissible. If you are not following any rules, then you might want to have the timing gear machined narrower and use crank shims to set the crank endplay correctly. You may also pin punch the sidecover and gasket surface of the block (this is more for keeping sidecover gaskets from blowing out, but it will also increase your endplay a thou or two. Gaskets are available in .005," .009," .015." and .020." You can mix/match and stack up to 3 max. (again for WKA)


My guess is that the bearing you used is not chamfered (machined) for the radius on the crank. You can do this carefully with a Dremel, or you can purchase the correct bearing for the application. If this is installed properly, my guess is that you will have endplay again.
 

foreverfaster

Premium User
Jimmy Glenn's Book
Everything you need to know.
yep, i have it at home as well,,.. its a tough read... well for me anyway... still plugging away...

Note: motor will be stock appearing class... rule adjustment for a couple of local bull rings... PZ carb is now legal with adapter for all flat heads as it is now a Briggs OEM part for racing motors.. HINT HINT for all you other tracks :)
 
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CarlsonMotorsports

Premium User
Oh man, stock appearing, then ditch that stock crank and put a stroker in it and be done with it....."there's no replacement for displacement."
 

foreverfaster

Premium User
thanks Brian, when i pull it apart again tonight, I'll check the contact between the crank and the bearing... the crank i pulled was machined on either side of the crank gear.. that could very likely be my issue.. thanks for the info..

G
 
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