Originally Posted by White Lightning
Tom, does the same theory work for larger bore/stroke/ larger CFM heads? Longer rods would still give you longer dwell time/slower acceleration/deceleration piston speeds @TDC/BDC? How long of a piston skirt does that type of combo like? Say if you wanted a 557" target cube, what would be the ideal bore/stroke/rod length/head CFM/RPM numbers?
It's kind of interesting in that the the Pro Stock guys today are running shorter deck blocks and shorter rods, therefore the L/R's are lower. When you shorten the rod the volumetic efficiency of the motors go up and this is a good thing, however using the old OEM heads of the past, you end up running out of cylinder head early in the RPM range. So, for the guys trying to use the original OEM heads, they are better off lengthening the rods in order to maximize performace providing they can offord to make that change. It's worth every dime if they can do it.
For the guys running the TFS A-460 heads or the Boss9 heads that have been ported and polished by someone that knows what they are doing the shorter rods would be your best bet providing they stay within reason. For example with the OEM heads you want to keep the L/R up around 1.8 and the TFS and Boss9 you can drop down to the 1.5 range. I was never into the long strokes. The maximum I would go was in the 4.00 to 4.25 range. Anyone ever wonder why the Pro Stock cars today went to the 5th gear? It's because they are operating in a narrower RPM range.
I love the chambers in the new Boss9 heads with the double quench design. I believe those work out much better on gasoline, however I'd like to see Jon perhaps experiment with raising the intake and exhaust ports on those heads to see where that takes him. Perhaps he already has, only time will tell.
I'd probably look at putting together a combination with a 4.500 to a 4.625 bore and either a 4.00 or 4.25 inch stroke with a set of TFS A-460 or Boss9 heads today. This would yield 509" with a 4.500"
bore and a 4.00 stroke to a 571" motor with the 4.625 bore and the 4.250 stroke. Any combination in between would also work as well, for example the 4.625" bor and the 4.125" stroke would provide you with a 554" motor. This is all higher dollar combinations as it would involve an aftermarket block that could safely be taken out to the larger bore size and rather expensive heads which takes us away from the topic of a "Budget 460's what did they run."