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I can't decide which cam to use for my jet boat engine. I currently have a Crane powermax hyd 290dur/495lift cam, but i'm concerned about valve float at 5500 rpm. Is it more advisable to go with a solid cam? Let's say 310dur/550lift, or is it a waste of money to convert?
I'm always all for installing a bigger cam, but usually for the wrong reasons (mostly the lopey idle). Now, back to the real issues...
Valve float is caused by a lack of valvespring pressure (inability to hold the valve closed) nothing to do w/ lifters
Good quality hydraulic lifters should be fine at 5500 rpm. There are plenty of high hp motors running hyd cams.
The only benefit of a solid lifter is that you'll have the opportunity to check the valvetrain often because the valvecovers will be off so frequently while you adjust valve lash.
If you are itching to do a cam swap, go for a roller setup. It'll require some mods(read that as $$$) but it's money well spent:cool:
Thanks for the tips. I have Comp Cams fast bleed lifters with the Crane cam all still unused yet. I can get a smokin deal right now on a complete top end package, the solid cam builders claim more stability for high rpm use. I'll flip a coin.
Never spent too much time in here, too slow. I've been reading up on old cam posts since your question piqued my interest. It looks like in a boat motor which can be run 30+ seconds at wide open, hyd lifters can collapse or do other wierd sh!t that wouldn't happen in an automotive app. Learn something new everyday.
PS. I don't think I'm the first to post on a topic I don't know enough about but think I do:D
For a jet boat with a BBC, I like a Tri-FLo type camshaft, with 10 to 15 degrees difference between the intake and exhaust. By Tri-Flo, I mean two different durations and lobe centers on every other Intake since every other intake runner is a different length. (ie: short, long, short, long.) Sig Erson used to grind a cam like that, but you'll have to find his son John, or brother Babe. Haven't heard from them in years.
When automotive people talk about high rpm they seldom think 5,500 is high. It is high for us boaters, but 6,500 and up is what most automotive race engine builders consider high. Hydraulic lifters are the only way to go in a 5,500 rpm engine. All hydraulic lifters are variable duration lifters to a degree (they bleed down). They cut down on duration with a small amount of bleed down at low speeds, particularly with stiff valve springs. Combine this with low oil pressure at idle and the actual valve open duration is reduced slightly at low speeds. At higher rpm the oil pressure is up and the inertia from the valve springs pushing down on the lifter plunger is reduced.
This is an advantage that hydraulic lifters have over solid lifters.
Dennis Moore
Originally posted by LeE ss13
For a jet boat with a BBC, I like a Tri-FLo type camshaft, with 10 to 15 degrees difference between the intake and exhaust. By Tri-Flo, I mean two different durations and lobe centers on every other Intake since every other intake runner is a different length. (ie: short, long, short, long.) Sig Erson used to grind a cam like that, but you'll have to find his son John, or brother Babe. Haven't heard from them in years.
I have used the Erson JB100 (228 IN, 240 EX@.050 & .542 lift on both sides) in an 18 Ft Marlin 455 Olds/Berk that was stock other than the cam and HEI. I was quite happy with it. I gave the boat to my daughter 4 years ago and it is still going strong. They have a JB200 that is slightly larger (235 IN, 240 EX@.050 & .542 on both sides). Very little difference, as you can see. The JB100 works well 2800 to 6000 rpm. I like to cruise at about 3000 rpm, so it works real nice and isn't too bad on fuel consumption. Check em out on the web.
SCUBA SKY or MUFF, NO DIVE TOO TUFF.:wink: :D