how to measure your port timings
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Cheers, Darrell. I ran my figures back into the calc to check I had that right. eden's one does take a negative figure for piston out the top.
"Our dilemma is that we hate change and love it at the same time; what we really want is for things to remain the same but get better."
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ok ross,
i never checked your info, is yours correct?
was a general reply to tavs question
i never checked your info, is yours correct?
was a general reply to tavs question
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I think those were the figures from the final build, certainly the transfers match the original port map I took.
If I recall you took a little of the bottom face to drop the barrel and raised the exhaust by 2.4mm and lowered the inlet by 1.3mm.
still not run it yet tho'
Will let you know when I get it going...
If I recall you took a little of the bottom face to drop the barrel and raised the exhaust by 2.4mm and lowered the inlet by 1.3mm.
still not run it yet tho'
Will let you know when I get it going...
"Our dilemma is that we hate change and love it at the same time; what we really want is for things to remain the same but get better."
Evening chaps,taken some measurements of the ports with digital verniers and have the following measurements.
no packer plate piston protrudes 0.9mm
ex =180.73
in=128.51 blowdown =26.11
0.5mm packer plate piston protrudes 0.4mm
ex=182.63
in=130.91 blowdown =25.86
1.0mm packer plate piston 0.1mm below barrell top.
ex =184.53
in =133.28 blowdown =25.625
going to use pm25 exhaust and sx200 gearbox 4.9 final drive ratio,
any advice on which way to go,dont want a too peaky engine with narrow power band.
strange the blowdown alters,although the port heights are the same ,anyone know why ?cheers all.
no packer plate piston protrudes 0.9mm
ex =180.73
in=128.51 blowdown =26.11
0.5mm packer plate piston protrudes 0.4mm
ex=182.63
in=130.91 blowdown =25.86
1.0mm packer plate piston 0.1mm below barrell top.
ex =184.53
in =133.28 blowdown =25.625
going to use pm25 exhaust and sx200 gearbox 4.9 final drive ratio,
any advice on which way to go,dont want a too peaky engine with narrow power band.
strange the blowdown alters,although the port heights are the same ,anyone know why ?cheers all.
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run it as low as possible(no base) for best results that your looking for
blowdown changes as a result of the stroke increasing/decreasing transfer duration at a greater rate than it does ex duration
blowdown changes as a result of the stroke increasing/decreasing transfer duration at a greater rate than it does ex duration
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thanks darrell,will go with your recommendation.
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do check the piston skirt clears and the cylinder spigot as mentioned before ,a 2mm head gasket will give u approx 1.1sq making it more torquey on the comp ratio ,u might want to burette the head though to check its safe enough
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hi,darrell,i did take 1mm off the piston skirt,but must admit havent checked the spigot bottoming out in the crankcase yet,
a 2mm head gasket will take the squish out to 1.9mm,will this be ok,
i will check the head volume and work some figures out,cheers.
a 2mm head gasket will take the squish out to 1.9mm,will this be ok,
i will check the head volume and work some figures out,cheers.
right have measured the head volume with my daughters calpol syringe,and near as dammit, it measures 40cm3
piston protrudes .9mm
head gasket 1.5mm
add .6mm height in volume,so head volume =42.3 cm3
height from ex port =33.2 +.9mm piston protrusion =40.1mm
vol= pi x rad 2 x h = 154.3cm2, shared by 42.3 =3.64 : 1 corrected
i also get 5.54 : 1 uncorrected
piston dome has'nt been allowed for which will raise them,but they seem a bit low,my heads hurting now cheers all.
piston protrudes .9mm
head gasket 1.5mm
add .6mm height in volume,so head volume =42.3 cm3
height from ex port =33.2 +.9mm piston protrusion =40.1mm
vol= pi x rad 2 x h = 154.3cm2, shared by 42.3 =3.64 : 1 corrected
i also get 5.54 : 1 uncorrected
piston dome has'nt been allowed for which will raise them,but they seem a bit low,my heads hurting now cheers all.
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didnt know head had a rebate thought piston was +.9 out top on a std head
best to either grease top ring and tdc it, fill to top of plug thread then deduct thread volume 2.3cc
or grease piston to squish band fill to top of plug deduct 2.3cc and add the squish volume eg 1mm vol
best to either grease top ring and tdc it, fill to top of plug thread then deduct thread volume 2.3cc
or grease piston to squish band fill to top of plug deduct 2.3cc and add the squish volume eg 1mm vol
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