Rmchrgr,
The J/SA national recoed is 11.37.
The K/SA national recoer is 11.57.
J/SA Class Index is 12.75
K/SA Class index is 12.95
Rule of thumb is a hundred pounds is worth a tenth. That's not ALWAYS true, but is close, more often than not.
The significance of that is this: There is .2 of a second separating J and K in both records and indexes (indices?)
Your engine with a 4bbl is factored to 210hp.
J is 12.50 pounds per hp; K is 13.0 pounds per hp.
What that means is, you only have to add half a pound per hp to move from J to K.
"J" is the car's "natural" class, at 12.89 pounds per hp.
Ideally, you'd only lose about a tenth going from J to K, because you'd only have to add 105 pounds. But, the index is TWO TENTHS slower... making it a better deal.
Looks to me like K is a MUCH beter deal, for another reason: The shipping weight on that Valiant is ony 2792 pounds. I had a '64 Valiant with a 340 and a 4-speed in it (cast iron 4-speed) and it weighed 2105 with 1/4 of a tank of gas.
At 12.50 pounds per hp, you will only have to weigh 2,635 (without driver.)
That is four hundred an seventy pounds less than my 2-door post '64 Valiant weighed.
I can't imagine how you could legally get iit that light, and you NEED to be that light, strategically, if you're gonna run "J."
At K weight, you'r Valiant would still only have to weigh 2,740 (not including driver), which is better, but still pretty light.
It looks like K would be the better deal, and the advantage would be about a tenth of a second, both with regards to the index and the record.
Food for thought...
Good luck with this; I think it would be a VERY viable and fun car to build!
Bill
