572 vs 598
 

So, I’m having the motors for my Cafe gone through this winter and we’ve been planning on rebuilding them to the same 4.5/4.5, 10.2, single 1050 configuration they are currently, but... The other day I was skimming through a thread on here and the OP was planning a 572 build, someone asked “why dont you go 598 if your going 572?” This got me thinking, maybe the positives and negotives are obvious but for the sake of good conversation and talking about motors, what is the good/bad/ugly in this comparison? So the Dart big M can go max bore of 4.625 so theres not a ton of meat left if something goes wrong, right? A variable in my build is we’re going to a set of Iron Eagles and putting my Big Browdies on the shelf for now probably. Unless they end up being mint; doubtful.. Is there some decent power to be made up by going bigger cubes since we’ll obviously be dropping the compression ratio for the heads? I’ll be running 91. Anyway I was bored and floating around out here off Long Island so I thought I’d ask..

curious to read the answers!

Ya right... are your rods 6.7 currently

One thing is the cylinder rigidity could be less with increased bore (thinner wall), ring seal is compromised.
Marine raw water cooled engines corrode so I like more 'meat' in the wall.
Head gasket has more deck area between the pistons.
Of course if not putting too much strain on the deal, then 'there's no replacement for displacement' LOL.

I went down this road with short deck some time back. You'll get old school and modern school answers. If you currently have 4.5 cranks and 6.7 rods with 4.5 bore you might just consider opening up to 4.560 for refresh and go 580 and leave some oops space. 15-20 ci or so isn't gonna make or brake it.

What current combo?

Yeah, I’m pretty sure the Eagle rods in there are 6.7s.
I’m not at home so I cant look at part numbers.
The corrosion arguement seems valid, thanks for pointing that out.

4.5-4.5-6.7 or do you mean all the rest of the components?

You wont have a problem with a big M at 4.600 in a NA engine the walls are still thicker than a 454. Like the iron heads on that combo.

Aren't those Siamese anyway?

I was thinking you still have .300 btwn cylinders if I'm not mistaking. Safely go 4.600 but some don't like the gasket.