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Reply to "1776 Head Replacement"

McGruff posted:
Pat Downs posted:

Good choice on the heads.

    My recommendation;  Use the swivel ball adjuster instead of the elephant foot when using a 1.25 rocket. The reason being, you will run out of travel on the elephant foot and damage it with the increased valve lift.

   Second, I also recommend running a little more compression. The combustion chamber of the panchito is well designed and the head runs cool. You should be able to run 9-1 compression with mid grade fuel, Although I recommend premium on any engine I build.

   If you wanted to take it a step further, get the chambers CNC machined to 61cc and then fly cut to 9-1. You will see even more power due to the unshrouding effect of the intake valve. When I designed the panchito chamber, I had to make it fit a standard 85.5mm bore. Unshrouding it increases intake flow 7-8 cfm, about 7 horsepower.


Thanks for the advice. I recalculated the static CR. My engine has an 0.65" deck height, so if I start with the 61cc chambers, flycutting to 45cc yields an 8.98:1 CR. Adding the price for the shop work brings the cost to around $1225 plus shipping. Not that I'm complaining, good components are worth the price.

The mor I think about it, my engine was built by someone unknown to me and  I have no idea what issues are hiding in the bottom end. Rather than throw $1200+ into a questionable build, it makes more sense to put that money towards a new one with a known pedigree. Surprisingly, my better half concurs. So I'll be starting a new thread about a new engine as soon as I wrap my head around my goals for the build and the other changes involved, like a bigger exhaust and carburetors, or possibly fuel injection.  

PM Pat Downs and have him build you a new motor. You won't regret it.