I have seen the 781 s crack but only in severe applications.
Bbc 781 heads.
15 years ago ibuilt a few of those engines and they ran good.
The 781 s have the most unshrouded chambers of all the oem bbc heads ever offered this makes installing 2 250 or 2 300 very hp tq beneficial.
Custom solid roller cam 10 2 1 compression dynoed on 91 octane bp gas.
496 bbc with cpm ported 781 iron port heads and intake.
I m running r44ts in my 469 bbc it has higher compression 9 5 an aftermarket mild cam along with bolt ons the r44ts run dark stay damp in around the base of the threads i know my carb is a bit on the rich side but i tried a set of r44tss they stay cleaner but i m still not sure if i like them i v always run ngks if at all possible the v powers are easy to read.
I have a set of bare 781 castings that were given to me my plans are to have the machine shop open the throats up to accept 2 250 in and 1 880 ex valves then i will bring them home and do some bowl and runner work nothing fancy.
I used stock lower ends with 11 to 1 closed chamber pistons and stock 781 heads with just a valve job and good springs.
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