Originally Posted by ap72
you don't need to have high rpm to benefit from a "fancy header" properly made you can see the benefits at whatever RPM you want.
true.. but.. the iron duke bottom end isn't strong enough to get the rpm's up high enough to run out of flow..
I understand that different tube lenth/size/ collector lenth/size/type can help...
g.m. got 6hp after a new head and roller cam.. and a balance shaft..
the newer head doesn't fit the older block..
'86 it got roller cam.. '87 disII ign ''88 oilfilter in pan (IIRC) balance shaft came online around now.. or allitle later