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Which roller cam for a 575sci rebuild?
Lost the head gasket in my 575sci between the cylinders. #4,6,and 8. Scuffed the wall a little on #6 cylinder. Stock head gasket showing signs of burn through on other head as well. 175 hours on engine. Currently running a whipple intercooler and small pulley. Planning on complete rebuild, keeping the stock heads and replacing the pistons with JE's, bumping the compression up to 8 to 1 from the stock 7.5 to 1. What roller cam would work well as an upgrade to the stock flat tappet. Current configuration should be in the 700-725 ish hp.
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Re: Which roller cam for a 575sci rebuild?
I had my stock one sent to Comp Cam to get specs for same switchover. I have a part number, but not tested. Who knows? Who has had real experience? I need answers too.
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Re: Which roller cam for a 575sci rebuild?
Richie Zul on Long Island does alot of rebuilds on the 575's.
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Re: Which roller cam for a 575sci rebuild?
How do you get ahold of Richie, besides trying the phone book.
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Re: Which roller cam for a 575sci rebuild?
Zul has a great rep but another thread a while back said they were rebuilding 575's retaining the flat tappet cam. I respect that and am sure they have their reasons. I thought surely someone here has put a bigger roller cam in a 575 and could give their experience on a cam profile as far as lift, duration and lobe separation. Not looking for trade secrets here to build my own engine but would like to be a little more knowledgeable before I ask my engine builder specifically what he's recommending for a cam and pistons. All I know so far is that they definitely recommended a roller over a flat tappet and 8-1 pistons.
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Re: Which roller cam for a 575sci rebuild?
Contact RMBuilder here on the site.He is a cam master,he has helped me out and a bunch of others here.I am sure he will share he expertise and help you out.
Nordic95 |
Re: Which roller cam for a 575sci rebuild?
zahndok,
I've got essentially the same set up you. I am adding aluminum heads, roller cam, and 8.5 pistons (think I'll be OK with the cooler running aluminum heads and intercooler) this winter. I too would like to hear from RMB on this subject. So Bob can you help us out??? PMs are OK by me if it's secret info! Thanks, Steve |
Re: Which roller cam for a 575sci rebuild?
Originally Posted by zahndok
I thought surely someone here has put a bigger roller cam in a 575 and could give their experience on a cam profile as far as lift, duration and lobe separation.
BTW: Since these are injected a computer reprogram may be needed. |
Re: Which roller cam for a 575sci rebuild?
I bet the new Merc 525 cam would be good in a supercharged application. It has the same specs as the old Crane 741 cam but with 114 lsa instead of 112.
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Re: Which roller cam for a 575sci rebuild?
Joey Griffin rebuilt both of my 575SCi's. He did what you want to do, bumped up the compression a tad, and put in a bigger roller cam. Runs like a raped ape AND gets much better fuel milage. Here's his number 252-946-1883. Be forwarned, conversation is NOT his forte'.
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Re: Which roller cam for a 575sci rebuild?
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 |
Re: Which roller cam for a 575sci rebuild?
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 :eek: . 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 |
Re: Which roller cam for a 575sci rebuild?
3 Attachment(s)
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" :rolleyes: :D ! Many Thanks in advance for your input and expertise! Regards, Steve |
Re: Which roller cam for a 575sci rebuild?
Originally Posted by PatriYacht
I bet the new Merc 525 cam would be good in a supercharged application. It has the same specs as the old Crane 741 cam but with 114 lsa instead of 112.
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 |
Re: Which roller cam for a 575sci rebuild?
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.
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Re: Which roller cam for a 575sci rebuild?
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. |
Re: Which roller cam for a 575sci rebuild?
Originally Posted by brianshelton
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.
But I do know he "bumped up the compression a little". So far, I am happy! Both motors run well and use less gas. |
Re: Which roller cam for a 575sci rebuild?
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.
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Re: Which roller cam for a 575sci rebuild?
Hey Bob (RMB),
Any suggestions??? Thanks, Steve |
Re: Which roller cam for a 575sci rebuild?
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 |
Re: Which roller cam for a 575sci rebuild?
TTT
Anybody else have any input on the best lobe separation for a blower motor like this? Most threads I've read on blower builds didn't have 110 degree lobe separation. Thanks |
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