This months Hot Rod magazine is one of the best I've seen in a long time.
There is a large article debunking the myths of Bore vs. Stroke. Even if
you choose not to believe their results, it's a worthy read.
They basically take two blocks, same heads, cam, manifold, carb. One they
give a large stroke with a small bore, the other a large bore with a small
stroke. They wind up with the same displacement. Next they put them on the
dyno and compare the results.
Are strokers better at low-end torque? Are short stroke, big bore engines
better at high rpm. Amazingly, there is only a negligible difference
throughout the rpm band (like 3hp).
It's a very informative article.
Next is pit stop (letters about tech stuff).
A reader writes in that he wants to improve his stock 289 heads with larger
Chevy valves. I did this 15 years ago and found the results amazing. This
confirmed it. They did say that it is important to not just add the valves,
but to port the heads. I was lucky at the time and was able to borrow a
cylinder head off of a Shelby GT350 and match the porting to the work Shelby
had done. The oversized valves and port matching just added to the
improvements. Their answer is quite lengthy and informative, but not quite
correct as I remember it. I did not modify the valves at all, they advise
you to buy custom ones. In the end they flow test the heads and post the
results. Here's the high and low from the chart:
at .100 lift on the cam (all flow numbers are in cfm)
Intake stock 44.3
Intake ported 81.0
Exhaust stock 26.5
Exhaust ported 49.0
at .500 lift
Intake stock 184.5
Intake ported 211.4
Exhaust stock 92.5
Exhaust ported 144.3
Again, worth the read.
Travis
B9472584
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