Hey Guys, I'm at a crossroads. I've been on a 2 year quest to get my new motor going and it's been a bit of a challenge. I started with a Mill Mitchell aluminum block. Went with the 4.500 bore and 4.375 stroke (557") with a set of indy ez-1's fully ported. Well... long story short I thru a rod cap on the first pass. Ruined 4 rods, 2 pistons, a crank and the block needs 2 sleeves. The block is currently being fixed by Bill and Roy Barton. Since I started this whole project I ended up getting a set of indy -1's. They have the big 2.250 intakes and are aggressively ported. I had them flowed and at .900 they flowed 409 in / 300 exh. So this is my question... Beings I have to buy half of the rotating assy again. Would it be better to just step up to 572"? would the heads make more power on the 557" or the 572"? or do you think it wouldn't make that much difference?

Everything else being the same, the larger cube engine would make the same power at a lower rpm point, so you wouldn't have to rev it as high. But with a bigger cylinder head, the game changes a little. Max flow on the -1's isn't relevant if you are still using the old cam that doesn't come anywhere near that amount of lift. You need to check the lift points within your cam lift. I don't really think there would be a drastic difference in engine operation with only a 15 inch increase in displacement, anyway. The bigger heads will be the game changer for you.

What type of rod? std. cam height block? Whats the min. cross section on the heads? But my opinion would be bigger is better when it come to cubes. That doesn't necessarily mean it will be faster.

Totally feel your pain....Never looked into a 4.375 crank availability, but I can tell you after killing my 4.75 crank once, the 4.5 is much easier to find...So a 572 would be the most common size and easiest to find parts for....And believe me, waiting months for parts....sucks.

As a bracket/index racer I've heard the argument the 540 combo is the best. I have found the 572 with the -1, 2.25 intake combo to make decent power at the 7000 rpm level. Maintenance has been minimal. Spring, lifter and bearing checks.
Doug

I was thinking the same thing about parts availability. I was told by the guy that flowed them that the cross section was about the same as a 572-1 but, I don't have dimensions. I'm using steel rods and the block is stock cam height.

Doug, I was wondering the same thing about the 540.

I was going to start with the cam I already own and then grind later to optimize. The cam is a Comp roller lift will be .800/.760 w/ 1.6 rockers and @ .050 286/300 on a 112 centerline.

ok, so it will fit. It will probably make more torque, and max power at a lower rpm. Sounds like a win win for a bracket car.

The 2.7% displacement change is less important than the curve of cylinder pressure & vacuum per degree of rotation, which varies with rod ratio. The smaller "n" ratio from longer stroke is slightly more tolerant of nitrous and mistakes in ignition timing, also captures more volume at the same IVC point which makes it more tolerant of cams with late closing.
OTOH it frequently needs more OL and/or tighter LSA (if the combo is well developed now).
Personally I favor more stroke to lower the RPM, and a longer rod to get the thrust vector back where it was.

Mine is 15-1,7.100 Molnar rod, similar cam, Indy 440-25 with 2 Eddy 750. Been best of 9.04@148,3340lbs
Doug

Polyspheric, it's always good to have the logic behind the reason. Once again you've gone beyond that. thanks you

Doug, I would almost be identical. All the way down to the same weight. Only difference is I have a match port Indy 3x manifold. 9.0 sounds damn good to me. Itching for that 8.99 on a perfect day.