head gaskets vs. compression ratio
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Tourer
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From: western slope Colorado
head gaskets vs. compression ratio
so upgrading my pistons to "high" compression @ 8.5. measured the cometic blue used gaskets @ .034", new james black with metal insert @ .045. no problemo. my question for the old timer pan builders( not that I ain't old myself) is, was the original gaskets for these just a metal head gasket. and if so what was the thickness? I'm thinking like the old cage motors of about .010-.020". so if that was what the old compression ratios were taken from than with the current gaskets the ratios would end up loosing a 1/2 to 3/4 of a point! would they not? so a 7.25 ratio pan motor would after being rebuilt with current gaskets be way down in static compression to about 6.5 to 1! any and all schools on the matter appreciated......... heck just measured my clearance between cylinder ring and head groove and after all clearances figured in, I have a .060 gap in between . seems I could mill the head a little to close that up. Like I said not familiar with these so all ideas welcome. btw; this is my 56 pan with an std lower
Last edited by 31choptop; Nov 3, 2013 at 12:13 PM. Reason: add crap
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From: la la land jerzey
YOU hear about milling all the time and in some cases it works and the end product is more power -- having said that milling the heads changes the angle the intake fits the heads < think about it / it drops it down -- not as much on a pan BUT what is it now / a gap between the head and the manifold ??? if none what than
2 ) the original gaskets on pan heads was a composit / asbestos and it did not have a fire ring that came later and it was .040 thick, made with the original materal that had a soft alloy or tin center with the gasket materal that would melt < that is the only way i can describe it ) and that was the seal the melt 1/2 would stay on the jug and 1/2 would be stuck to the head when removing the head on a used motor --
you will not see any difference you can feel or hear with gasket changing on a pan they are not that efficient somewhat shovel and the best would be an evo with a carb - johnjzjz
2 ) the original gaskets on pan heads was a composit / asbestos and it did not have a fire ring that came later and it was .040 thick, made with the original materal that had a soft alloy or tin center with the gasket materal that would melt < that is the only way i can describe it ) and that was the seal the melt 1/2 would stay on the jug and 1/2 would be stuck to the head when removing the head on a used motor --
you will not see any difference you can feel or hear with gasket changing on a pan they are not that efficient somewhat shovel and the best would be an evo with a carb - johnjzjz
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Tourer
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From: western slope Colorado
thanx John, so what yer sayin is Im over-engineering this rebuild! just check every thing , hand fit the pistons and slap her together. do you happen to know why there are no specs. for assembled/ installed over all valve height in the books. sure make it easy to see if the valves are sinking low in the seats
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Tourer
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From: western slope Colorado
I have a clymer book and it only shows free spring height, not assembled
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Tourer
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From: western slope Colorado
so John, what would the assembled height be of the valves from spring seat to spring retainer or valve tip
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From: la la land jerzey
its always measured between the upper and lower retainers - for some reason harley uses fractions instead of decimals
on the seat the outer spring length and pressure is 1. 3/8 " = 105 / 115 pounds
with the valve open its measured at 1 inch = 180 / 190 pounds
the max travel is 1. 31 / 32
inner spring 1. 3 / 16 = 25 to 35 pounds on seat
inner open pressure 51 / 64 = 70 / 80 pounds
max travel - 1. 23 / 64
on the seat the outer spring length and pressure is 1. 3/8 " = 105 / 115 pounds
with the valve open its measured at 1 inch = 180 / 190 pounds
the max travel is 1. 31 / 32
inner spring 1. 3 / 16 = 25 to 35 pounds on seat
inner open pressure 51 / 64 = 70 / 80 pounds
max travel - 1. 23 / 64
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