Re: 1976A Dyno Run
Posted: Tue Sep 22, 2015 10:10 pm
Ian, very nice results. Thanks for sharing.
It is interesting that raising the ports by 3.5mm ( spacer plus extra gasket) did not tun it into a rev mad race bike with no bottom end. It simply raised the curve at all revs but more at the top and gives a pretty good idea of what happens when a motor is freshened up. I suspect that raising the intakes also helped to bring back some of the bottom end that might have been lost if the transfer and exhaust ports were raised by that amount by porting alone.
The speed at which it peaks was raised but with no downside at all.
The pipes added some at the top end but are clearly street pipes because they did not raise peak revs at all. Yes they lost a little HP below mid revs and gained a lot at the top end but overall they were a nice improvement and much lighter than stock pipes too.
If you would like more top end, try raising the exhaust port roof to increase blowdown time and exhaust duration a little.
It is interesting that raising the ports by 3.5mm ( spacer plus extra gasket) did not tun it into a rev mad race bike with no bottom end. It simply raised the curve at all revs but more at the top and gives a pretty good idea of what happens when a motor is freshened up. I suspect that raising the intakes also helped to bring back some of the bottom end that might have been lost if the transfer and exhaust ports were raised by that amount by porting alone.
The speed at which it peaks was raised but with no downside at all.
The pipes added some at the top end but are clearly street pipes because they did not raise peak revs at all. Yes they lost a little HP below mid revs and gained a lot at the top end but overall they were a nice improvement and much lighter than stock pipes too.
If you would like more top end, try raising the exhaust port roof to increase blowdown time and exhaust duration a little.