[Fot] TR3 vs TR4 crank, differences?

[Tim Murphy]

I'm thinking of prepping a crankshaft for our TR4 vintage racer.  I have at
least one TR3 crankshaft, a TR4 crankshaft and one or two other unknown
spares.  Are there any differences or are they the  same and can be used in
a TR4?

 

I first plan to have it crack checked and checked for straightness and size.
The next step would be balancing and lightening possibly?  Is there any
significant advantage to polishing the crank, other than that it looks real
pretty?  Then I was going to have it bead blasted and nitrided and finally
ground  with the proper radiuses and fillets.  I have to review Kas's books
to check for other tips.  I've got CRS disease (Can't Remember Stuff) and
it's been awhile since I read some of those books!

 

Thanks for the info and any other tips on crank prep.  Once I've got the
"new" crank I'll install it on the following rebuild with the thought that
with the forged pistons, Carrillo rods and the "new" crank, we should be
able to use 6500 RPM reliably.

 

Tim & Ryan 1961 BRG TR4 #317