rmbuilder

To best provide the most accurate information I would need to be clear on the changes being made in the original platforms. Are they both 575 SCI?

Zahndok,

You will be raising the C/R to 8:1, all other parameters remaining the same, with a 750 HP target @ ???? WOT RPM.

Steve,

What cylinder heads will you be running? C/R will be raised to 8.5:1. Target HP @ ???? WOT RPM?

Both Hyd-Roller?
Engine management?

Bob

zahndok

RMB
My Platform is a 2002 575sci that had already had a low profile whipple intercooler installed with small boost pulley. Fuel system was upgraded to aeromotive A1000 with appropriate larger plumbing. Egt port was added to exhaust and ECU re-programed on water.

Plan now is to retain factory iron rec port heads after valve job.
Block to be decked and pistons changed. Hyd. roller cam added with appropriate lifters. Plan to keep stock Crane gold rockers.

Currently my max rpm was 5300-5400 wot. I'm OK with setting the limiter to what provides the best durability.
My goal would be a little more hp on the top at wot since I have plenty of low end torque already. Have broke the drive twice already . Seems I could afford to lose a little on the bottom to gain on top.
All advice here on appropriate parts and brands is welcome
Thanks, Dave

Steve Zuckerman

RMB,
Thanks for the reply. I value your knowledge tremendously.
My current setup is:
2001 575SCi, with AZSM boost kit, Whipple low profile intake/intercooler, 3" blower pulley with 7PSI boost. The motor was totally rebuilt about 250 hours ago with Fel-Pros and Clevites. Been running well since then. Blower rebuilt by TBS 15 hours ago.
Boat is a 2001 Nordic 28' Heat, single step. Currently runs 85MPH @ 5500 with 1.5 Bravo XR/standard length Imco case lowered 1", and 28" blueprinted Hydromotive P-5X. Similar #s with a blueprinted 30" B-1. I'm estimating current HP @ 700 PSHP, because that's what it takes to get a Heat to 85. My and other Heat owner's buildups show that it takes 17 HP to get 1 MPH over stock. I would like to see mid 90s, which would take 175/200 additional HP by my estimate. Peak HP at something like 5700/5800? Limiter reset @ 6000 (currently 5600, which I do hit with a light load).
I think there should be some easy HP found with a more aggressive hydraulic roller cam, aluminum heads, an increase in compression, and ECU reprogramming.
Currently planning to go to 8.5 pistons, Dart Pro 1 Marine anodized aluminum heads, and a cam/lifter/spring combo of your recommendation.
PLEASE FEEL FREE to tell me if I am on the right course. If not, like Ross Perot used to say, "I'm all ears" !
Many Thanks in advance for your input and expertise!
Regards,
Steve

Steve Zuckerman

PatriYacht,
I hear you. I have several friends running C741's in their blower (roots and centrifugal) motors, and they all seem to be running strongly. I agree that that the 525 cam might be even better. The HP that Whipple is pulling out of these motors (800+) tells me that the cam and aluminum heads are working well with their blower and intercooler (I have a Whipple intercooler now).
Thanks,
Steve

BKSAE

BillR, Did Joey Griffen give you any info on compression and cam. I did talk to him, but he seems to be booked for a long time. The problem with going to a different cam with stock pistons is low compression. Bigger cams simply won't work. Found aout the expensive way-changed the cam. By the way, don't trust ASM on cam choice.

tomcat

Aren't your 256 blowers pretty well maxed out now? You can improve the heads and cam but no more HP unless you spin the blower even faster.

AS&M made 875 HP on the 525 EFI so those heads and cam are good, but it took a much bigger intercooler and a much more efficient blower to do it.

BillR

No he didn't. Plus if he would have; I am not sure if I would understand what it all meant. I know enough about motors to make me dangerous - if ya know what I mean. . . .
But I do know he "bumped up the compression a little".
So far, I am happy! Both motors run well and use less gas.

BKSAE

BillR, I understand it about as well. I'm being told to go a certain direction, and don't want to throw good money after bad. Just wanted to see if all indications are similar. From what I've gathered, the low compression of strock 575s does'nt lend itself to bigger cams unless the compression is changed. Then the fuel needs to be considered, heads, etc. etc. Might as well save money and buy newer boat. The odd thing about it, after doing Arizonas upgrade with pulley, ECM, and Superchiller, I got better gas mileage too-above 1 mpg.

Steve Zuckerman

Hey Bob (RMB),
Any suggestions???
Thanks,
Steve

zahndok

Bob,(RMB), you posted these specs for a stock 575 bump stick on a previous thread. I'm wondering which specs jump out at you that are particularly detuned by Merc. In other words would you tend to increase or decrease durations, lifts, or lobe separations from this stock reference. I understand that different heads and pistons effect selections but are there basic beginning changes that are a no brainer? Thanks for educating us.

Dave


Crane single pattern
Lobe H 240/329
300/300 @.0042
240/240 @ .050
148/148 @ .200
.559/.559
105 ICL
115 ECL
110 LSA
INTAKE 43 BTDC 77 ABDC
EXHAUST 83 BBDC 37 ATDC