Closest comparison I can hands on relate to is I've built a number of Mitsu turbos to about 2Bar or ~30psi. Mitsubishi 4g63's have short rods ~(1.6 IIRC) and long strokes too and (believe it or not) can make close to the same (4-5 HP/cube) and RPM as BobR's Ford.

Side loading primarily leads to accelerated ring and bore wear, (the durability "issue") and obviously that builds HEAT, scuffing of the pistons/bores can happen in ANY motor if the oil film breaks down/cokes and the engine load is high enough for long enough.

Excessive side loading?, obviously not....I would only define Excessive as leading to damage and/or loss of power. But more side loading than an equivalent displacement 430" shorter stroke motor, definately. Not excessive but maybe significantly closer to it....

Those dart blocks have mega-thick walls compared to OEM, thinner bores move around more than thick ones.

bobR, do you have the 302 or cleveland Mains?
Just curious.

On a 9.5" deck windsor the big end of the rods do get up in the cam at anything over about 4" with steel rods, I have a 4.17" stroke 427 and also had to relieve the big ends and run a reduced base circle cam. the proximity is something you try not to think about when you're