Mercury 557 cu. in. naturally aspirated
 

Mercs used the 557 block for a long time now (900sc, 850/1075sci), would a 557ci N/A engine make sense? Basically make a 525efi using the bigger block, should make 700efi HP or so.

I realize they have the 700sci, and its been reliable but the 91 octane and the blower raise the initial price and operating cost and I would assume maintenance costs with the blower.

Reliability and maintenance may be better with the N/A along with 87 or 89 octane. Should be lighter and last longer between overhaul as well. I assume Torque should be close to the sci as well.

Just curious of others thoughts

would be a very expensive 700hp motor, just buy an Ilmor, lightweight, 2 year warranty, tons of torque, runs on 89 octane, n/a hard to beat

Ateco Engines make a 540 CI N/A that will make 700hp carb or EFI. I think it makes perfect sense. However you will need to run premium gas as it will have higher compression to make that kind of power. I have talked to him about building 598 CI that should be around 750-800 hp.

alum heads and back the timing down a bit and big cubic inches and they make a lot of sense !

RHC

Dart has a 765ci monster block out now, should be able to make 950-1000hp N/A.

Probably 95% of the engines I build are 598 ci. I love the bigger inch engines since they are very torquey. If you take a NA engine that makes 1.25 hp/ci, then it stands to reason that the more inches you have, the more power you will make.
A 557 ci engine at approx. 10:1 will make 700-725 hp with ease at about 5300-5400 rpm. You could make more than that, but you will have to spin it harder and have enough cam to make it pull to about 6000 rpm. You will obviously need 93 octane. If you want to run 87 or 91, it will cost you some power since you will need to lower the static compression.
If you are going to build a 557 like Merc., you will have to buy a 4.375 stroke crank. If you are going to do that, you might as well just buy a 4.5" stroke crank and do more inches. The 2 cranks are probably the same price, and the 4.5" crank is probably easier to find. Let me know if I can help in any way or if you just have some questions.
Eddie

If your thinking of putting a bigger bottom end but still using the stock 525 intake,etc....forget it. You'll never get enough air through it unless you do alot of port work to open up the plenum/intake.

Agreed.

and BTW: I made 540's out of 500EFI's. At 9.75 compression we were only able to get 630HP (fully dressed on a dyno) out of them. I'm told a good carb set-up could have made approx 30-35 more because I need more air.

I believe Tyler Crocket has a modified intake for your application. I thought is was close to coming on the market.