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Bored&Stroked · 12-02-2023, 10:44 AM

I have original Harley KR jugs and heads - they were relieved and also had a very different head design. They ran mostly flat-top pistons until later in the 60's when they tried a dome top. The dome top engines didn't make any more HP than the flat-topped piston designs. Of course, these were purpose built racing engines and ran way past 6000 RPM all the time. Flow was everything to their design, with huge ports, big valves, etc.. We only wish our Ford flatheads had anywhere near the type of ports and head-bolt layouts of the Harleys.

When I designed our FlatCAD chambers, heads and pistons (flathead Cadillac Bonneville engine) - we used as much of the 'KR' design as possible - including the custom mods that Jerry Branch made for his modified KR's.

Branch (and my neighbor 'Snuffy Smith') made some of the highest HP KR's of the day. I learned a LOT from Snuffy! Snuffy built a KR for use at Daytona for a rich guy back in the early 90's - was making about 60 HP on a 45 cube KR on gas. The guys running the dyno were really surprised about the HP he was able to achieve on the good ole' KR sidevalve motor.

12-02-2023, 10:44 AM	#13
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,178	Re: Shoud I relieve my block I have original Harley KR jugs and heads - they were relieved and also had a very different head design. They ran mostly flat-top pistons until later in the 60's when they tried a dome top. The dome top engines didn't make any more HP than the flat-topped piston designs. Of course, these were purpose built racing engines and ran way past 6000 RPM all the time. Flow was everything to their design, with huge ports, big valves, etc.. We only wish our Ford flatheads had anywhere near the type of ports and head-bolt layouts of the Harleys. When I designed our FlatCAD chambers, heads and pistons (flathead Cadillac Bonneville engine) - we used as much of the 'KR' design as possible - including the custom mods that Jerry Branch made for his modified KR's. Branch (and my neighbor 'Snuffy Smith') made some of the highest HP KR's of the day. I learned a LOT from Snuffy! Snuffy built a KR for use at Daytona for a rich guy back in the early 90's - was making about 60 HP on a 45 cube KR on gas. The guys running the dyno were really surprised about the HP he was able to achieve on the good ole' KR sidevalve motor.