cylinder head packer for imola.

[rosscla]

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

[bazza3004]

All good info rosscla and very much appreciated. as previously stated mines the imola with the 'drop in head' (for want of a better term) so il be on the fone to cam lam for one tomorrow to see what thickness head gaskets/ packers they stock for the kit as with the combustion chamber step of approx. 1.2 mill I will either need about a 2.5mm packer/gasket of combination of head gaskets that will amount to this to now obtain the squish. I realise this would not be ideal but if I cant get one in the thickness I require I don't see what else I can do other than use more than one.
I will also readily admit I don't really know what im talking about on this subject an so have no doubt im talking shite

[bazza3004]

just a quick update, ive now rebuilt the motor and its running fine just need to get it set up at psl on dyno. managed to get the squish to 1.2mm and from best I can measure the port timings are exhaust.. 180, transfers ... 124. cheers baz.