EKHKHK56 wrote:Well 68-69 were fast years for H-D with Cal Rayborn setting the first over 100mph Daytona in 68 and lapping the field in 69...with basically a 40 year old design. Of course Cal was extremely good at coaxing machinery to get around the track! Neat stuff, very nice to see photos of these. I have a set of 52R heads that have the standard porting. I'll dig them up to compare.
Simon wrote:One of the racing cylinder sets I used to have came with pop up pistons with the flame front edge beveled. Interesting to see the mods everyone tried back in the day.
EKHKHK56 wrote:The number stamped in W series heads like a 5 or 6 means combustion chamber size. 6 had more squish than 5. For KRs not sure but in the Jerry Branch article it says to use #7 head the latest design (1965). As far as 59 and 60 numbers in the book and on the head that's a good question. You would think they would list a 60 head if the book is newer than 60 if they were different. Could just be overlap between book and part and it's same head? My 52R heads are identical to the ones you posted. That's the design that got the work done for many years!
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