difference between 4hp flatheads and 5hp flatheads?

#1
I've got a 4hp flathead, everything looks identical to a 5hp flathead on the outside, what are the differences with the internals?

I'm looking to buy a billet rod and a different cam
 
#2
um not the best with them but the bore and stroke . ther both the same basic block just a few parts changed . maybe pm the restore kid he knows more on them :shrug:
 
#3
Had the same question/problem. External is same. All the internals less the valves seem to be different. Best bet if you wanna use a 4hp block and upgrade is getting it bored for the 5 hp piston. TRK chimed in on my old thread "4hp Kool Bore" Some info to comb through if ya already haven't.
 
Top