557 vs big cubic inches
 

I realize that 557 ci isn't a small displacement, but compared to what is being built out there -- 705 etc--- it is on the modest side.
So why is it that the bigger builders like merc, sterling and others have been using the 557 platform for so many of the big hp builds?
is it the fact that they can spin them faster to make the hp and still stay together? i can see this as a major plus with the cats...
If someone wanted to build some 1100 - 1200 hp engines for a 12,000lb boat what would be the best cubes to start with?
This would be a pleasure V/ poker runner, top speed would be great around 100mph, cruise at around 65 mph.

Any input is welcome.

Thanks, Dave

I could be mistaken, but I think 557 is about as big as you want to go with standard 9.8 deck height.

1100+ hp gets difficult on pump gas on a standard 572. I imagine 632's with 1671 or whipple 5.0's should get the job done reliably.

565 is about the best combination I'm told by 3 of the big name race engine builders(sonny's, reher/morrison, shafroff) using a short deck...the real long stroge big cube engines are hard on cranks...even the high $$$$ ones

i've already got the tall decks -- can still make a smaller ci with tall deck -- and utilize longer rods to help rod geometry.

So it is more of the tall deck vs standard deck issue is what i'm hearing?

Most of the top builders use the tall deck 10.200 for the 557ci.

Delsol, what were your motors originally? BTW, beautiful boat! I remember seeing it at loto some time back.

Bore, Stroke, Rod length for that combination?

4.5inch bore , 4.375 stroke, 6.535 rod length, tall deck block

+1 you will want to start with one of these!

Attachment 492836

Thank You

rotating geometry,

I had forgotten about this thread.... Thanks for bringing it back to the top

Thanks for the compliment coolerman, Parnell did a great job on it

My engines were originally 632's ci, I had always thought that the bigger ci was better for torque, and might still b true for a N/A engine. But the more I look into it there is more to it with the blown engines, and having a solid bottom end is essential when making big hp.
I've never been a big believer in revving engines into the 6-6500 rpm range for no better reason than maybe just not used to it --and more chance In my mind to fail.

as stated, the 557 is the best combination for reliably its a combination of shorter stroke and longer rod that gives it the wiining edge, a rod ratio of 1.5 x stroke is desired minimum requirement when building one of these blower monsters!! (1100/1200 hp...) this is my professional opinion, others may say different, but I want my sh*t to live!!!

I've seen many engines built by various engine builders utilizing rod and stroke combinations that are "way out there" in thought... it's really simple when one thinks of what's actually going on inside the engine... the pin height should be comfortable, in other words not crammed up the pistons butt!! when the pin is way into the oil ring, it is subject to an extreme level of heat and limited cooling effect from oil spray, even with the use of bottom end oil spray rails, the piston,pin, and rod bushing life is severly diminished... the use of thermal barriers (coating) helps, but in no way eliminates this condition, the only way is the right way, keeping the pin at a comfortable distance away from the heat!!! again, IMPO

the "perfect" combination is 4.375" stroke with a 6.635 (.500") long rod.. coupled with a 4.500 bore will give you the "557" this recip assembly in a 10.200 block will allow for a compression height of 1.370 allowing sufficient room to square deck the block for blueprinting purposes...