DO NOT UNDER ANY CIRCUMSTANCES CONSIDER BORING A 74 OR LATER 360 .060"!!!!
Okay, I can stop yealling now.
Early 360 blocks were the same castings as the 340, so it could be safely
bored out to about 4.08 without too much concern. Later 360's get dicey at
4.04. It is possible to go 4.06. Usually that would involve a Super Stock
eliminator engine builder looking for every ounce of power who has many
blocks to chose from and painstakingly sonic tests them all while step
boring them.
Let's say you want to build a 408" 408hp engine. 1 hp per cubic inch. A
worthy goal in a NA engine. 1.1 is doable but gets less streetable. Going
from a .030 bore to .060 bore gets you 6 cubic inches at the 4 inch stroke.
That's 6 HP. BTW I get 414ci with a 4.06 bore and 4" stroke. Probably
rounding error with one of us or both! No biggie, doesn't change the point
of my argument here.
Now the problem. One of the real keys to performance is true round, non
tapered bores. The thinner you make the walls by overboring the more flex
you get and tougher it is to get true bores and good sealing with minimal
friction. It's a problem BOTH with the ability to bore the engine with
thin walls accurately AND the flex you get during operation. A double hit.
You will give up WAY more than 6 HP if you lose good sealing. And you've
made your block less durable and probably lost the ability to ever rebuild
it!
I suggest the most minimal overbore needed for a cleanup. You'll see more
and more .020 pistons being stocked, because with moly rings minimizing
wear, .020 will clean up most high mileage engines. At least Mopars!
Overboring is NOT A GOOD WAY TO FIND POWER!!!!
As for the 4" stroker? Go for it! I think that package is going be really
big now that cheap 4" cranks are readily available. I bet you'll even see
companies like Ross stock pistons especially for the combination if they
don't already. KB might even do it soon, for a really affordable option.
Be happy with 408ci!!!
-STE
I don't know what plugs to use, but I know a few things about how to build
consistent reliable horsepower.
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