Quote:
Originally Posted by Jeff Lee
One the one hand it seems senseless to hash over this but on the other, my comparison to valve lift makes sense. Well at least to me...
If NHRA has a spec indicated in their books (deck height / rocker ratio) and in the end all they care about is a minimum volume between the top of the piston @ TDC & the chamber and a valve measurement @ maximum valve lift, then why publish the deck height or rocker ratio?
My way of learning NHRA class racing engine blueprinting is if NHRA gives a spec, it is to be adhered too. Not "adjust according to what is convenient". Man, I've spent some money on OEM rods (before after market rod acceptability) adjusting the big end to obtain the exact deck height I desired.
Now I'm wondering why NHRA publishes anything more that the throttle blade diameters on a carb.
And if NHRA specs a positive deck (say a 383 mopar) and I run a negative deck instead, I can save on possible piston to head interference issues and I can probably run a tighter LSA for more power.
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Jeff how confidant would you be with a zero deck height spec? Can you be sure the bearing didn't wear a bit, or the rod didn't stretch a touch? And as far as piston to head problems won't a thicker head gasket achieve the same thing?
If you can't build in a little safety margin you are going to get tossed for stuff that won't help performance one bit.