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900sc - broken valve spring

Old 09-10-2002, 02:12 PM
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kwb
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Default 900sc - broken valve spring

I got 90 hours out of my Merc 900SC before finding a broken valve spring while checking the lash. No other damage - wow!

I think for now I'm just going to replace all of the valve springs with the same ones that are in it so that I can get some more boating in before winter.

Should I change the lifters at the same time?

This winter I was thinking about pulling the engines and changing over to a hydraulic setup instead of the solid roller I have now. What are the pros and cons with the solid vs hydrauic lifters?

I cruise at 4200 RPM and have a max RPM of 6200. I have a long idle (40 minutes) to get to the breakwater. I usually go 20 minutes on each engine (alternating) on my way out.


Thanks.
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Old 09-10-2002, 02:20 PM
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Default replace it

Replace the springs, and rollers. Do a complete valve job it you can. If not you can replace the springs on the motor. I guess it depends on what you want to get out of the motor. But I would say a max of 50hrs on those solid roller lifters is enough. 90hrs is way past due, if you ask me, but I am no professional. I put a bunch of motors together with solid lifters, and had them break a few times. It sucks when they do, it usually wipes out the cam.

The new hydralic cams a pretty good these days. You may find no difference in performance. Give crane a call.
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Old 09-10-2002, 03:03 PM
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You will have to lower your rpms at wot.
The hyd roller cams are safe up to 5800rpms but after that your going to bounce your valves.
ISKY carries a line of springs called "Tool room Gold" in my opinion they are the highest quality spring avaliable.
They also have a good custom cam grind for that size motor, i can e-mail or post later.
We used it in my 557ci SC's
I would do this now because you've been lucky so far.

One other thing is maybe pulling the heads over the off season and making sure you did'nt push any sets back into the heads...and of course a valve job.
Mark

Last edited by Back4More; 09-10-2002 at 03:10 PM.
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Old 09-10-2002, 03:27 PM
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kwb
I agree 90 hrs. on solids you definetly got your moneys worth. I switched back to hyd. roller,idles better lost a little bit of power,mainly in high rpm range.I still turn 6100 rpm and have 180 hours on them with no trouble.They need adequite spring psi to make them live.
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Old 09-10-2002, 09:17 PM
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KWB: I talked to a guy today and he said that your replacing ALL the springs is definatly the way to go at min.. He also said that if you were ok with loosing a couple RPM's then you can go with the hyrolic but you will have to lower your RPM's.

Hey in regards to tunes. I have come up with some cool ideas that I will have to role past ya. It involves a swinging screen that can go for the inside and the cockpit

Jon
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Old 09-10-2002, 11:48 PM
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KWB,

I agree with the others who have said not to run the hydraulic roller cams/lifters much past 5800rpm. Actually, I wouldn't wind those engines much more than 5500rpm no matter what cams were in them. Because of the easier/lighter spring pressures of the hydraulic rollers, they are less apt to break as a mechanical roller set up. From what I have been told, hydraulic roller lifters don't like to run much more than 5500rpm because they don't always follow the cam profile which eludes to a valve float condition which can break. They can't handle the spring pressures that mechanical rollers have, but this is one reason why mechnical roller engines break or are more profound to break. Lots of spring pressures are hard on parts. Hydraulic rollers are much easier on the valve train and you don't have to worry about periodic valve adjustment.

Mechanical rollers do make power but you're going to eventually pay the price either in high maintenance costs or broken parts. Get the hydraulic rollers and set them up for UNDER 5800rpm---I think you'll like them.
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Old 09-11-2002, 02:50 AM
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Some great advise guys..... Thanks!

I just don't want to give up any HP - you know how it is........ You have to pay to play, not sure I want to pay for a new engine if I loose a valve though. Hydraulic may be the way to go.

Audio - when are you coming back? I'm ready to do the stereo / dvd deal.

Ken
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Old 09-11-2002, 07:27 AM
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If you are running solids you have to stay on top of things. They make good power and rev limits aren't as critical as with hydraulic cams. Checking valve lash and spring seat pressures is a must when running solid rollers. If you are going to stick with the solids it would be a good time to check the spring seat pressures and then compare them with the new springs. If you use the same ones you can gage how they are doing by the seat pressure at a given time. If they are sagging close to where they are now at 75 HRS, it is time to change them. It is also would be a good time for lifters, as others have mentioned. If you do go to a hydraulic cam be sure to get enough duration to keep cylinder pressures in check or you will end up with detonation problems which can be worse than some occasional springs and lifters. Just my .02! Good luck!!!
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Old 09-11-2002, 08:25 AM
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KWB: I am trying to figure out a time to get out there maybe late Sept? October is a no go as my girlfriend has to much work. I have two weddings that I am working around. I should know sometime soon. After that it is November. I will be out there for Thanksgiving because she can not get out of town . So maybe if it all works out well, I can hook up with you on my trip in Sept, then we can do the install in November?

Jon
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Old 09-11-2002, 09:29 AM
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Default springs

kwb

Definitely change the lifters on the mec. rollers, the Isky's have worked the best for me. They have a sleeve around the axle providing more surface area. If you decide to go to a hydraulic roller watch your boost, it will problaby change. Also consider a rev kit, it will help keep the lifters on the lobe and eliminate the weight of the lifter. It may add a couple hundred rpms without screwing with the hydraulics.

Last edited by JimV; 09-11-2002 at 09:31 AM.
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