mountain80
Member
First of all a BIG THANKS TO FOUREASY for sending me down this road by telling me what head he used and I ran with it from there.
Well as some of you have been following I have a Dellorto Phbg with a machined bushing to work with the stock manifold. I have finally got my Puch head welded and redrilled today. The combustion chamber was remachined by myself as i cc'd it and was at roughly 13:1 uncorrected versus my modified head at 8.2:1, to high to run even on premium fuel.I set the Puch head at 8.7:1 for now as it has 160 psi cranking pressure. Can always go back and remachine for higher compresion if need be. Spent alot of time doing the calculations but it came out well finally today. Had headgasket sealing issues as I drilled out the holes but the cyinder had a radius that came to close to the redrilled holes and leaked combustion pressure up through the studs so a reweld/ redrilling on a milling machine was in order. Also remachined the OD of the combustion chamber as it was smaller then the bore of the cylinder. Heres a few pics of the head hope to get it reinstalled and tested this weekend. The Puch head has roughly 50% more cooling area then a stock head and has a squishband instead of the stock PK hemispherical chamber. Note the sandblasted finish, this is a trick 2 stroke aircooled guys used years ago to increase the surface area for more cooling and also the set of 3 holes on each set of pependicular fins for more cooling.
Well as some of you have been following I have a Dellorto Phbg with a machined bushing to work with the stock manifold. I have finally got my Puch head welded and redrilled today. The combustion chamber was remachined by myself as i cc'd it and was at roughly 13:1 uncorrected versus my modified head at 8.2:1, to high to run even on premium fuel.I set the Puch head at 8.7:1 for now as it has 160 psi cranking pressure. Can always go back and remachine for higher compresion if need be. Spent alot of time doing the calculations but it came out well finally today. Had headgasket sealing issues as I drilled out the holes but the cyinder had a radius that came to close to the redrilled holes and leaked combustion pressure up through the studs so a reweld/ redrilling on a milling machine was in order. Also remachined the OD of the combustion chamber as it was smaller then the bore of the cylinder. Heres a few pics of the head hope to get it reinstalled and tested this weekend. The Puch head has roughly 50% more cooling area then a stock head and has a squishband instead of the stock PK hemispherical chamber. Note the sandblasted finish, this is a trick 2 stroke aircooled guys used years ago to increase the surface area for more cooling and also the set of 3 holes on each set of pependicular fins for more cooling.
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