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.

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.

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

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.

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 :D:D

Jon

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.

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

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!!!

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

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.

Which company makes a rev kit for the hydraulic roller?
Thanks

rev kit
 

Comp Cams makes one for tall and short deck. I dont think there is one for the crane lifters because of the design of the body.

Thanks Jim. I'm using Crane. What is the reliability of the Comp Cams hydraulic-roller lifters? I have about 42 hours on my Cranes (fingers crossed)

lifters
 

So far no problems with the comp lifters. We are checking/changing them at 200hrs. I have run them up to 400hrs.

BTW I can get lifters but the supplier wont sell them without a cam purchase. Kind of a Bull s$%t deal. Also their more expensive.

KWB,
I've thought of switching from a solid roller to a Hydralic but don't want to lose any power.
So I've been doing allot of research and talked to allot of people and hydralic rollers are allot different than I thought.
I've talked to a pretty reputable company and they are making power up to 8000rpms with hydralics, and they are using spring pressures as high as the solid roller stuff. They assured me that they could make the same if not more power than my current solid.
Myself being the skeptic decided to stay with the solid roller for now, I did switch lifter manufactures though, from Comp Cams (broke 2 in 80 hours of use) to the Crower severe duty .
Your pretty lucky to get that many hours without breaking a lifter. Do you have rev kits on those motors ? I kind of believe that rev kits help the longevity of the lifter unfortunatley I have Gen6 blocks and they don't make a rev kit for them.

26scarab--

What company did you talk to???
I am planing on going to hyd. roller cam this winter ( have solid flat tappet now)

I have had problems with all solid rollers including the comp cams. I puked one (comp) on my own motor after 10 hrs. Usually the exhaust lifter will go first. To use a mechanical roller spring on a hydraulic cam doesn't make sense to me. Its hard to believe the hydraulics will work with that kind of spring pressure (600lbs+) over the nose. Lifter bounce seems to be the biggest cause of failure with a M/R not to mention they are brutial on the rest of the valve train. To overcome this the cam needs more spring pressure to keep the lifter from leaving the lobe. The wear patterns on the worn lifters that I have inspected are not at the 6:00 position. The ramps are less agressive on the hyd. roller to keep it out of float and make the hydraulics work. The reason for using the hydraulic roller is they are more reliable. The spring pressures are less so the lifter doesn't see the load from the spring 380-400lbs and the shock load from lifter bounce. Another point, I have seen some H/Rs with cast cores. If you try to put a M/R lifter on these there is a greater chance of failure. I had to rebuild a motor for a guy because his engine builder put M/R lifters on a H/R cam. Every lobe was severly damaged. As always my opinion

Just a dumb question that maybe JimV or someone else with dyno experience can answer. Does a hydraulic roller or a solid lifter flat tappet cam have more HP potential? My Erson catalog lists some mean solid cams. Here is an example for BBC blower application. 254/264 @ .050 with .645" lift on a 114 LSA. RPM is 3500 to 7000 RPM and the cam says dual quads on 6-71 or larger blower with 8-15 lbs. of boost!!! That is a big cam, but if Jesels are used valve lash adjustments would be minimal and on a 572 with 8:1 comp with a chilled 10 lbs of boost through good heads with CMI's would make major HP. No rollers to break and reasonable spring life and RPM potential deep into the 6000+ range. What have some of your experiences been? I have seen solid flat cams at the drag strip, and they do pretty well. I haven't seen to many real race cars running hydraulic cams, flat or roller. Oh ya these cams and lifters are cheap. Maybe we are buying what the salesman makes more commissions on with the roller stuff???:D

With a 900 sc, can you really keep the rpm in check with the blower spooled up and running hard?

I run a Big Chief head with long valves which can be a little hard on valve train.. I started out using a s/r with crowers's cutaway severe duty lifter and tool room springs at 250#. Cam was .714" Average life was about 50 hours at a cruise of 3500 rpm. Did this twice. Went to a crane h/r with .632" lift and 150# springs. Made about the same hp at 5500 as s/r cam, lost about 100 hp due to lower rpm. After 105 hours, almost all cruising I had one rough lifter in each motor. Went back to s/r, cut the cam back about .030 in lift, added a KE lifter spray bar in intake valley, used crowers same lifter but with the extra oiling hole to lube bearing axle and lowered springs to 210#. So far, I have 115 hours, check lash every 5 hours just to make sure nothing changes. So far so good. My thought is that if it works with this config should be even better with a lighter valve train??

With a 900 sc, can you really keep the rpm in check with the blower spooled up and running hard?

I run a Big Chief head with long valves which can be a little hard on valve train.. I started out using a s/r with crowers's cutaway severe duty lifter and tool room springs at 250#. Cam was .714" Average life was about 50 hours at a cruise of 3500 rpm. Did this twice. Went to a crane h/r with .632" lift and 150# springs. Made about the same hp at 5500 as s/r cam, lost about 100 hp due to lower rpm. After 105 hours, almost all cruising I had one rough lifter in each motor. Went back to s/r, cut the cam back about .030 in lift, added a KE lifter spray bar in intake valley, used crowers same lifter but with the extra oiling hole to lube bearing axle and lowered springs to 210#. So far, I have 115 hours, check lash every 5 hours just to make sure nothing changes. So far so good. My thought is that if it works with this config should be even better with a lighter valve train??

Tinkerboater, JimV,
Check out www.lsmeng.com
He is one of the places I talked to about hydralic roller cams.

Rebuild valve train after 50 hours
 

KWB
Check out your Merc owners manual, they say that you should rebuild the complete valvetrain every fifty hours! People may have good or bad opinions about Merc High Performance but one thing that I have learned from dealing with them is that they do a lot of endurance testing on their engines (much more than any local engine builder can afford to do!). You may get a lot of different opinions about what to do but I would think long and hard before changing the set up. This is hard for me to say because I tinker with everything! Please read the owners manual over and over again until you have it memorized, it really helps!
Sincerely
Dennis Moore
Mercruiser Master Tech
writer for
FAMILY AND PERFORMANCE BOATING MAGAZINE
author of HP Books
BIG BLOCK CHEVY MARINE PERFORMANCE
SMALL BLOCK CHEVY MARINE PERFORMANCE

Dennis, what does a complete valvetrain rebuild mean? New springs and lifters or does the heads need to come off to do valve seat / guide work? Just curious, I run a solid roller in my motor also with slightly more duration and lift than the 900SC cam and feel 50 hrs for springs and lifters is about right for me also. Hopefully nothing else though!!:confused:

Valve rebuild
 

I never got around to asking what the Mercruiser High Performance Division had in mind when they suggested a complete valvetrain rebuild after 50 hours! Even when I worked for Hallett Boats (almost 9 years) we didn't see many 900 SC engines. On the few 900 SC engines that we serviced I suggested that we rebuild the valvetrains on the engines and everyone looked at me like I was nuts! (what did I know, I was only the mechanic!) Even very knowledgable boaters can't believe that this type of service work is required after only 50 hours of running time. If it ever would have come down to rebuilding the 900 SC valvetrain I would have inspected everything and only replaced parts that looked worn out (or ground the valves if they needed it).

I would say that to make 900 horsepower that the camshaft has some really fast opening and closing flanks that require high spring pressures to keep the lifter following the lobe. The stiff springs puts extreme pressure on the lifters/lobes at idle (when the engine is running at high speeds the upward inertia of the lifter counteracts the downward pressure of the spring relieving some pressure on the lifter roller but at low speeds you have less upward inertia of the lifter, this creates excessive downward pressure on the lifter/lobe from the stiff valve springs). This would make camshaft and lifter INSPECTION (not necessarily replacement) very critical. You should find out as much as you can about these parts and learn the signs of failure.

Closing the valves very quickly with a combination of steep closing flanks on the lobes and stiff valve springs would be very hard on the valve seats. Owning a 900 SC for any length of time would mean investing in a good valve spring compressor, periodically remove the heads and inspecting the valves and seats for damage (learn as much as you can about valves and seats). It might be economical in the long run if you also invested in a valve spring tester. These two tools could save you some money by fortelling future engine failures (knowing when to replace the parts) and give you confidence and peace of mind in your engine while you are out boating.

No one (but the boat salesman) said that owning a 900 SC would be easy.

Sincerely
Dennis Moore
Mercruiser Master Tech

The big chief heads did they have stainless valves or titanium? Thanks

Wow, how things (technology) have changed since the originality of this thread in 2002....i.e., lifters both hydraulic and solids, head gasket technology too....just all kinds of new and improved stuff out there now.....almost 15 years later! :)

Initially we had DelWest titantium on both. Then stuck an exhaust in the guide and DelWest suggested getting the titantium out of the exhaust side with the low cr of 10:1. Eventually got rid of the Big Chiefs and went to a Canfield head. Realizing you can't compare heads. Also went to 8-71's and intercoolers which helped make up the dif. But life was good with KE's spraybars and Crowers SD solid rollers in the revised config. Still replaced rollers every 125 to 250 hrs. Used the Isky 8200+ spring and replaced every 250 hours. Jessel went thru rockers every 250 hours. Never a failure.