New 1100hp BBC build.
 

I'm building new big blocks for a 42 OL and want to be in 1100hp range. They'll be carbed with 10-71 blowers. What would you guys build a 572 or 557ci tall decks? It currently has 900s 542ci. Always running them 5k rpm plus and was thinking a shorter stroke would be better for longevity? It will be dry sumped, hyd cam, shaft rockers, dart heads. I know there's a lot of experience on this forum and would like get a few opinions. Thanks in advance!

Bigger is Always Better....................

Think you're gonna need bigger blowers if you want to make that power at reasonable boost levels.

I know Valako has a couple of 540/871 or 1071 builds that are conservatively over 1k hp over on the Lake Huron side of lake MI. Not sure if their on OSO or not but if so I'm sure they'll chime in. Jim V said it took many by surprise.

If you do go 557 I know offshoreexcursion here has two new sets of pistons for you. In swap shop.

Need more details on the boat before we can give advice on which combination would suit you the best...The 572 idea is good but there are different combinations to achieve that and I tend to lean towards the shorter stroke bigger bore with a long con rod ... feel free to hit me up if ya wanna chat

Sell everything you have now. Call Mercury Racing. Wait for truck to show up.

1100 hp with roots , carb, under 600 cubic inch , and a small blower is not a reality . At least not on pump gas .

Billy Boats is correct, especially with the key factors of running hard for long and reliability

Are these scratch built or are you rebuilding your current engines?

What parts do you currently have that will be reused?

Agreed... better to be conservative and safe!!

I remember seeing this 598 a while back in the swap. I can't validate build nor dyno sheet however thought I'd post it for the heck of it anyway. Pump gas? There was no build sheet but I'm assuming.

I know 1000hp is possible all day with a 1071. I know 1100hp is asking a bit much of a 1071. So what i take of it is big cube is better. Im leaning towards bigger bore shorter stroke.

JJ your box is full

I've done 565's and the best I got was 1050
They were not very reliable due to sensitivity to fuel octane

4.600 bore
4.25 stroke
Dart CNC 355 heads
Solid roller 262/272 .714 lift
8.6 static compression
BDS 10-71
Lee intercooler
2 1000 cfm 4150 carbs Tried every carb known to man !!!!!
Daytona sensor ignition with map sensor ( best thing I ever did)
11 % over drive 8 lbs boost
Jessel timing
Jessel shaft rockers
Piston oilers
904 lifters
Steff oil pan
Bryant Crank
Carilllo rods
The best HP they made on a steady state pull was 1051, but on a sweep the were 1030. So in reality they are 1000 HP . That's the most your going to
Make on pump gas. You can put a killer tune up for the purpose of seeing a
Big number on the Dyno but it's never going run and last in the boat. Please don't take any of this as negitivity about your build ,but I've spent more money than I'd ever admit trying to squeeze 1100 from these engines and from what I learned there's just limit to 10-71 and pump gas.
PS I've also tried changing compression ratio vs boost levels and there was never a real difference

Some pretty good advice and well given. Just curious if ftn is a step or not and what kind of speeds you got with it with your builds.

Your avitar not real clear but now that I look it appears newer ftn. Only asking cause I'm doing 555 sc builds for a 12 meter. 8.25:1 comp builds.

My boat is a poker run edition , yes it has the most current step bottom . With my current engines with 1150 hp tune I ran 156 mph
With the previous engines 146 mph

Good info thank you! Im good with a 1000. Just trying to reuse the 1071s without jumping to 1471s. I see you went with a shorter stroke on your 565.

Emptied my in box.

I like the 4.375" stroke the best I think it's the best combination without side loading the pistons too
Much . Also seems to be a good tq to HP ratio with 4.375. I like the 4.25 stroke for lighter faster boats because they seem to rev higher and you have better prop/ gear ratio options with higher rev engines . Some guys like big engines spinning them slower making BIG tq then turn a big pitch prop. My experience is that a prop turning faster works better on a cat or very fast Vee

I don't blame you. Where abouts you located?

The 4.375 is what I'm shooting for. There's an interesting pair of 1671s from the alex and ani boat for sale. Definitely a pair of power makers but just to big I think. Located in Mass.

16-71 would be too big for your application . Blower sizing is important to
Make a combination work. Stick with the 10-71 , with 572 ci , 8.5 compression and 7 lbs of boost you'll make a legit 1000 hp with 900 plus ft lbs torque . You will probably see 1050-1070 on the Dyno.

That's quite the bogus dyno sheet, wonder where it was dynoed at, do you remember where the guy was from selling it? 1000 observed hp, corrected to 1178 and bsfcs that are almost 1 lb per hp!

What about freshening what you have, sell the 10-71's carbs, chillers etc and switch to whipples, mefi4 and a new cam?

The block is at it's max bore and would need to be sleeved. I put new rings it before keywest 2 seasons ago. The motors run great but its time and just easier to stick with what we got. I'd probably just go merc 1075 if I were to get rid of everything.

47excaliber and I were just talking about this on the way home.could copy the engine build thats in his boat,I'd go w/ bigstuff3 but thats me.

Big stuff is nice, was just thinking expense. Mefi will save a few bucks.

Remember I'm just passing on info posted. Lol


http://www.offshoreonly.com/forums/s...u-1200-hp.html

Oh my...

You are smart to freshen before major problems! Good used blocks sell easy for decent money, might want to look into new blocks. The merc 1075 is cool but I wouldn't give up on your rebuild yet. :ernaehrung004:

What parts are you considering reusing from your existing build?

We won't be sleeving the old blocks, just not worth it. New dart blocks and heads with new internals is it what I'll be using. Everthing else will be reused.

Seems like your mind is made up, just curious what is current bore on the blocks? They start at 4.44 on the 900's but that's was many years ago

Fwiw.

Icdedppl swapped out 871's, for 1071's, on his 540s. What it took to make 6-7lbs of boost with the 871, was 3% over. What it took to make 6-7lbs of boost with the 1071, was 3% under. Roughly a 6% decrease in blower speed. It reduced the blower speed, from 6,180, to 5,820 RPM at 6000 Engine RPM. So, about 360 RPM of the rotors.

Going from a 10-71, to a 14-71, all things being equal, (no hi helix or anything ), you're looking at about a 10% change in blower overdrive, to make the same boost/air movement. So, if you're running a 1071, at 20% over making 8psi, the 14-71, will probably get it done at 10% over.

Those changes, will net a change of about 600rpm reduction in blower speed, at 6000 engine rpm. A 16-71, slightly more. Figure the 16-71 will get it done, at about 5% over. Again, all things being equal.

From what I have seen, on the dyno doing some testing with a 10-71 Littlefield with a blower shop intercooler, was that, the increased overdrive, didn't have much if any affect, on the intake air temperatures. At 6psi, 870hp, 8psi, 930hp, and 10psi, 1000hp, the intake temps stayed in the 110-115 degree range during the pulls. I believe to make 10lbs, the 1071 was at or around, 20% overdrive, I don't remember the exact ratio. But the temps stayed good, and the power kept going up, but we figured enough is enough.

On my personal engines, I saw a slight increase in intake air temperature, going from 1:1, to 8% over. About 10 degrees increase. Temps were still below 110 degrees at 8% over. At straight up, they barely hit 100 deg during the pulls.

Out in the boat, held at wot, air intake temps at 8% over, stayed in the 110-115* range, even on hot humid days. thats with a 420 B&M, and Teague superchiller intercooler.

The non intercooled 10-71, at 3% under, runs about 135-140* intake temps, at wot in the boat. The only time it gets higher, is AFTER a run, and you come back to idle. She will climb to 150ish idling , then cool back down after a bit.

From my limited experience with roots blowers, is that, the power gains, are not so much, from 8-71 to 1071. Its just not a HUGE change. However, the power gains from those baby blowers, like going from a 177, to an 871, or a 250 to an 871, can be substantial. Makes sense, when you're reducing rotor speed, by in some cases, over 100%. In otherwords, a baby blower turning 12,000 rpm, to a blower turning 6,000rpm , at WOT.

just thought I'd mention it. I think billy boats has you covered. Run what you have, and enjoy it, or, switch to a screw, but skip the 16-71 .

Also, as Billy Boats said, going too big with a roots, or even a screw for that matter, can hurt torque. Screws like to turn some RPM, and Roots dont. Downside with slowing either of them down, is the efficiency at lower speeds can drop, just like it does with a roots at high speeds.

If you look at some dyno data, on engines with small , highly overdriven blowers, you'll many times see, boost start out say, at 7lbs, and by 6000rpm, they may drop to 5lbs or so. Say, with a 177 or 250 blower. But, you bolt an 871 on it, and the boost starts out maybe at 5lbs, and by 6000rpm, its up to 7lbs, which is the opposite. If I had to pick, i'd rather have a blower that maintains , within reason, within a pound or so of its max boost from 3000 to peak rpm. Of course cam timing, exhaust flow, etc, can affect those readings as well. (too small a cam will cause boost to stack up at high rpm)

For the most part, in my opinion, an offshore boat, should have a blower, that is efficient at higher engine speeds, rather than low engine speeds. If I was building a street 454, I'd opt for a 250 blower. For an offshore 454, I'd opt for the 871. An 871 lugging around at 1500-2000 engine rpm, is going to have a good amount of "carry back", aka rotor leakage, at low speeds. Basically, its inefficient there. A smaller blower, like a 250, will be much more efficient and responsive at those rpms, and you're not holding a street engine at 5500 rpm for 30 minutes.

good information joe,let me add by saying that the engine making 1000 with the proper sized roots will see a big gain in power with the properly sized screw blower due to less parasitic loss.

Just to throw this in and everyone can think I'm nuts but my builds are gonna be 555 871's with Valako promaxx 317/340 heads and only want to run enough boost to achieve 900 hp. I don't run all day long wot but do have a tendency to get on the buds and leave it pinned for unknown periods. Is what it is. Lol. my personnel goal is just 8.25:1 comp and like 5-6 pds to hit 900. Im not worried about it but drives are gonna be hating it regardless what I do unless I flipped and went back to NA. Even with SC the magic in the heads work miracles. Jim didn't even have a concern to achieve 1k plus hp even with an 871. Either way the 12 meter will be loosening up and free.

john,what cam did you decide on for these engines and what carbs?also will they be innercooled.

Has anyone dealt with steve morisson or nelson racing engines? Both these guys build some serious power. They both can make custom cams to your spec or will design one for you. It seems like they have it figured out .

Thats why i asked if you knew were they were dynoed at and who it was who had them for sale. I crunched the numbers a little bit at those bsfc's , would take almost 5 gallons a minute at those bsfc's to run them at 6000 rpms!

Steve morris is a big procharger guy. Not sure how much roots stuff he plays with. He does do some big power stuff !

[ATTACH=CONFIG]565243[/ATTACH]Here's an intercooled roots 8-71 547ci at 8.1 comp, running 10 pounds of boost on pump gas w/ Brodix 345cc intake runners setup this Winter by YPM. Dyno was performed w/ accessories and wet CMI E-Tops.

[QUOTE=SecondWind;4534391][ATTACH=CONFIG]565243[/ATTACH]

Here's an intercooled roots 8-71 547ci at 8.1 comp, running 10 pounds of boost on pump gas w/ Brodix 345cc intake runners setup this Winter by YPM. Dyno was performed w/ accessories and wet CMI E-Tops.[/QUOTE

What cam is in this? Off the shelf or a custom grind, solid or hydraulic?