Re: cylinder head packer for imola.
Posted: Sun Sep 28, 2014 7:31 pm
Ok then that will give you a blow down of about 29.8 degrees (exhaust - transfers / 2) different tuners have different opinions of what the ideal figure should be but generally a low figure, say 21, is not regarded as good on a 'tuned' motor but may be fine on a standard one. As I understand it the higher the figure the higher the rpm at which peak power may be delivered but that can also be influenced by other factors like where your pipe works and so on. People have built careers on working these things out
You have to bear in mind that the 60mm stroke will increase the transfer and exhaust timings and decrease the inlet, on a piston port motor, though the inlet should be 360 degrees on a reed valve kit. Run the same figures through the calculators with a 58mm stroke and you'll see what I mean.
You've added a 110mm rod which gives you some flexibility to adjust the timings by the use of different packers, 3mm ought to put you back where the kit designer intended but factor in the extra stroke and you end up with the piston out the top. Level is 0, out would be -1 or whatever you actually measure.
If you're now level at TDC, and just below at BDC then you're close. IMO you have now to look at the head gasket as the only thing you now have to play with. Pack the base up further and you end up with the piston further down at BDC.
An adult may be along shortly to elaborate
You have to bear in mind that the 60mm stroke will increase the transfer and exhaust timings and decrease the inlet, on a piston port motor, though the inlet should be 360 degrees on a reed valve kit. Run the same figures through the calculators with a 58mm stroke and you'll see what I mean.
You've added a 110mm rod which gives you some flexibility to adjust the timings by the use of different packers, 3mm ought to put you back where the kit designer intended but factor in the extra stroke and you end up with the piston out the top. Level is 0, out would be -1 or whatever you actually measure.
If you're now level at TDC, and just below at BDC then you're close. IMO you have now to look at the head gasket as the only thing you now have to play with. Pack the base up further and you end up with the piston further down at BDC.
An adult may be along shortly to elaborate