Why 557? What is the big deal?
 

After all this time why is the 557 bore and stroke so desirable?

Sterling 1550 & 1150 & 1700 Turbo are 557's
The New Chief 1900 turbo is a 557
Merc 850, 1075, 1200 yep they were 557
The Merc 1350 & 1650 are 552 (not 557 but why limit your flagship product when you did a clean sheet redesign?)

Sonny's is making bigger and bigger N/A power out of monster bore & stroke. Why arent marine guys doing it? What is this MASSIVE benefit that cant be overcome by displacement? The technology is there, what is the magic behind the 557?

Why not 598 or 632? Or like Sonnys 762, 770 or 864?

2 reasons that come to mind,1 the 4.375 crank is less prone to breaking than a 4.5 crank.2 more room for a nice ring package.these are things to concider in a high horsepower endurance engine.

not so long ago, 572 was the way to go.

it still is for me!

Exactly my point. Why arent we up to 632 or BIGGER now?

I would think it has something to do with piston speed and the amount of reciprocating weight.Them big car engines only do high RPMs for a short time.Boats do it for for longer periods.I would think they have a bigger chance of self destruction.Just my 2 cents JOHN SR

It also has to do with cylinder wall thickness, 4.5" bore verses 4.6" or larger. That's the reason the ZR1 is a smaller displacement than the Z06, they needed thicker cylinder walls for durability under boost. The big Pro Stock motors are billet blocks and 5" bore spacing or more. If you were looking to go NA than the 598's make more sense. You have a lot lower cylinder pressure and less stress.

Agree with all of above and will include the question of drives. Not much that will live behind the torque of a monster displacement engine.

Also the added mass of bigger everything moving at faster speeds would generate some serious loads on components.

A similar question came up 2 years ago. My take was that 557cubic inches netted the most reliable setup with readily available parts (as if that even applies to this industry). Curious also why merc stayed around that same displacement on their brand new stuff. Only thing I can think of is keeping the deck height within reason to keep the engine package within a certain dimension.

I agree with all of you, but the question behind the question was the 1350/1650. If you are going to go with a clean sheet engine design why so "small'?

Shouldnt that SOB been about 100 cubic inches more?

i understand what you are saying but a 557 and a 572 both have a 4.5 in bore.

It's probably because they get a good deal on parts. Aren't big companies all about the bottom line anymore? Who knows maybe in the next couple of years those motors will be assembled in China.

Probably many factors involved, target horsepower based on out drive rating, availability and cost of components, durability of combination etc.

i don,t think that,s it,a4.375 and a 4.5 stroke crank from callies cost almost the same.as far as [assembled in china],the mentioned engine manufactors would not last long if they sold foreign junk,we are talking about high end packages here not chinese junk.

Maybe it can. Does anyone know what the actual bore spacing and deck height is?

LT5s can be taken to 415s or even 440s with new liners a guy developed years back. It will be cool when the aftermarket starts boring and stroking the QC4V and adding bigger turbos. But it won't be cheap.

Virtually everything for LT5s was custom and cut from a billet when they got heavily modded. Like 5k for crank, 3-5k for cams, and 2k for headers. Expect the same but worse.

Hmmmm. Thats interesting. Wouldnt they design the drive AFTER the engine to meet its HP demands?

I know. I've just been on a bash China kick lately. I would imagine it has to do with wall thickness, rod stroke ratio, ect. And now a days you have to throw in the "green" factor. The merc stuff has converters don't they?

im with you on bashing the chinese junk,im not sure of the number but i believe the converters are only required below 500 hp.

mercury did . m8 drive.

Our 632's in the 33 have been great but a little high strung before the detune.
We have a 572 in the deck jet boat that took a s#$t after less then 1 season with a 1071 on top on pump gas so we pulled the tired 496 tall deck bus motor of the shelf and put the 1071 on top and bolted her in to finish the year,the 496 runs harder sounds better and go'es 8 mph faster then the 572 ever went.

I thought 540 was the magic number.

You cant hear it thru the screen but that was supposed to be sarcastic.

yep,guess i should have got that.LOL

i know the old merc 900sc,s were 542 cu in.bore&stroke was 4.440 by 4.375

The fact is, times are changing. 20 years ago, if you wanted big HP numbers, you had to go BIG. Back in the days when a 454 engine in a early 90's truck made a whopping 230HP. Now, you have engine with 100 cubic inches less, making upwards of 400HP off the showroom floor in the auto world.

Today we have fabulous cylinder head choices, and superchargers that are a far cry from what was offered 20 years ago. You need to think about something. These engines are making in some cases, almost 2.5-3HP per cubic inch with forced induction.

557 X 2.5 =1392HP.

572 X 2.5= 1430HP.

In the grand scheme of things, 38HP means absolutely nothing at the 1400HP level. 2-3% of total engine power. And, to make up 40HP at that level, well, theres a lot of ways to do it. I think what these guys are shooting for, is power, AND reliability. They probably like the thicker cylinder walls, shorter stroke for RPM and strength, and overall lighter rotating assembly. These engines are running the pistons way down in the hole, and I'm sure to get a respectable pin height and rod length, the shorter stroke allows for room in a 10.2 block. You also have to remember, you're working with a 10.2 platform. You only have so much room for Stroke/rod/piston. If you want to run a conventional style open chamber head, a reasonable piston dish, and keep a large squish area, you have to look at the options. A 4.750 stroke in a 10.2 block, just isn't gonna be an easy 7.5:1 high boost engine. Generally speaking, going from a 4.25 stroke to a 4.750 stroke, with same piston, same chamber, will bump compression about a full point. So say from 8:1 now becomes 9:1. Anyone know what size dish you'd need in a 632 to get to 7.5:1?

Im not sure if im making sense with what im trying to say. There is so many things that go into these engines from an engineering standpoint, I can guarantee the engineers at Mercury Racing, guys at Sterling, etc, know all about the 632CI, and sonny's big cubic inch stuff. However, they choose not to go that route, and I am positive its not based on cost.

I imagine we will be having a similar discussion 20 years from now as well. As technology gets better things will get cheaper to produce at this level and we will see more improvements across the board. Remember, 454s used to be big.......

I'm glad I stumbled across this thread.
It's great reading for me as I was having damn near the same conversation last weekend with one of my neighbors who I knock beers back with when he's not out working for their race team customers.
But his input was different, perhaps because of the nature of his sport.
He said for my refresh or rebuild or if I start from scratch is to go with the longer stroke and smaller bore for more torque as that's what my boat wants since it's always under a load while operating, and dump my dominators for a pair of carbs that are built to the needs of my current displacement at the chosen rpm range. He's told me from the get go that he had no idea why Merc put these huge carbs on such a small displacement engine.
I've always taken his insight as the Gospel itself as he's enjoyed a lifetime of racing, tuning, and working within their industry but not really with any boat racers. He said he'd build me a set of carbs to my needs or tell me what to purchase and tune them to my powerplants and for my boat don't aim for super high rpms but for more torque at lower revs for longevity since she ain't no speed demon anyhow.
I'm curious as to where I'd find an online chart noting which bore and stroke combinations net what displacements
and what combinations y'all or some of your friends have utilized with good success for longevity.
My powerplants are stock 525SC's with 500 hours. I have seawater cooled chillers beneath my blowers and smaller pulleys for more boost. I never go over 5100 rpm and I seldomly go there due to the time on my engines and would prefer not to start from scratch with bigger blocks but work with what I have even if I need to purchase a new crank and rods to go with new pistons which I already figured I'd have to purchase.
As always thank for y'alls insight, I've always got great info from this forum from you guys.

Thanks,
Kelly

this is the formula,bore times bore times stroke times.7854 times number of cylinders.

Kelly. Hands down, the best bang for the buck in a 525sc, is a cam, head, and most importantly a blower swap. I am making 800HP and 740FTlbs with 468ci with 6.5 lbs of boost on pump gas. It's a docile engine. The dominator carb wasn't the limiting factor on the 525sc, the blower, flat tappet cam, and GM iron heads were.

505 cid is the magic number...out fontana engine made 3000 + hp and lived 1/4 mile!

As not to hijack this thread I'm starting another one. "525SC's"

See ya,
Kelly

Harder to make boost with a larger engine also, that needs to be taked into consideration.

not on the turbo deals