390 vs 408

1wild&crazyguy said

.060 360 =372cid
390/391cid 18 cube diff

Big bore with short/er stroke=hp/tq with emphasis on hp.

big arm with lil bore=mostly torque think 225 slant 6 but without the cubic handy cap.

built the same while compensating @.050 dur for the cid increase on the 390 and both having cid matched port volumes, the cid will reflect the power.

If just built the same, the 390 should make close if not more but at a lower rpm.jmo

But there too many variables.

Click to expand...

Justin....... *this has taken a lot out of me to ask this, hey, I am growing... LOL*

What are the chances of you having a set of heads, and access to a flow bench, to see the difference between a 3.94 bore and a 4" bore? I have always heard 4%, 10%, 10HP per .010......... It would be nice to actually have some numbers. Not to mention I would think the bigger thebore, the smaller the difference would be...... in other words, the difference between 3.91 to 3.94 would be greater than say 3.94 to 3.98......

Just a thought.