General consensus is 3 - 4 % more power in favour of the iron block (upto 40 hp @ 1000hp) due to ring sealing, you will also lose more if you are using some sort of boost. With more modern aluminium blocks it's reputed to be less though. Whats worth more, 30 hp (@ 750hp) or the 150lb weight saving ?
You also have to look at availability, how many iron Mopar blocks are available with a 4.84 bore spacing ?
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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