Cam and valvetrain longevity....??? low duration high lift...
09-21-2016, 07:05 AM
#251
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To keep this on point, way back after first install I believe it was, you said you needed smaller cams for more torque lower in rpm band. Correct me if wrong.
09-21-2016, 07:15 AM
#252
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I've done that w/ bbc's,,keep upping the duration.started to run out of boat.my 454's w/ oval ports.I stopped around 254ish on the intake.but I did have some compression in all the engines,and basically middle of the road ramp speeds.sure I gave up 5-20hp but those suckrs are still running.
my current engines,10yrs and the springs are still holding original spring pressures,,isky cams and lifters.
my current engines,10yrs and the springs are still holding original spring pressures,,isky cams and lifters.
I'm sure you'll get to a point, that the torque loss at low rpm, and idle quality, begins to degrade too much, to where , you simply went to far. I think in my example, the cam swap was for the better in that application.
I always wondered why, we should prop the boat, 1000 RPM higher than peak torque, and how peak torque, should be at 4000-4500 . WHY?
Why do we need peak torque to occur that early, and start falling off after that? If people say "torque spins the prop", than wouldn't we want torque to increase, not decrease when the throttles are held on the dash?
I do remember the days of installing cams with way to much duration, not enough compression, a crappy carb/ignition setup, and generally, a soggy street engine. But lately, I am thinking, that most fear duration a little too much. Alot of guys are running BIG engines these day. 540, 565, 572, 598, etc. If theres any engine out there , that can deal with a little extra duration, without such drastic side effects, its a big ci big block chevy. I've seen a few of them, with some cams that have alot of duration, idle very well, which shocked me .
I'm sure a 29ft'er with a single engine, might not want to trade off low speed torque. Lets say, a 29ft fountain with a single 540. He might need max torque down low, to get some good planing, and acceleration. He only has 650ft lbs available per say. Now, a twin engine 32 Fountain, with a pair of 540's in it? Install a pair of those same 540's in it, now he has 1300FT lbs on tap, in a hull that weighs a little more than that 29 single. That guy, could lose 50ft lbs a side, for a gain in upper rpm power, still have a boat that accelerates like a banshee, and screams at top speed as well.
I think that when a builder is building a combo, or a engine developer is spec'ing out a build, should consider the hull/application that the engines are going in, and focus on the actual performance of the boat, not just spec the perfect engine combo for the dyno. A big block chevelle that see's track only use, shouldnt get the same cam/heads, etc , as the one that gets to the track once a year, and 95% is going to car shows and ice cream parlors.
Just thinking out loud here.
I always wondered why, we should prop the boat, 1000 RPM higher than peak torque, and how peak torque, should be at 4000-4500 . WHY?
Why do we need peak torque to occur that early, and start falling off after that? If people say "torque spins the prop", than wouldn't we want torque to increase, not decrease when the throttles are held on the dash?
I do remember the days of installing cams with way to much duration, not enough compression, a crappy carb/ignition setup, and generally, a soggy street engine. But lately, I am thinking, that most fear duration a little too much. Alot of guys are running BIG engines these day. 540, 565, 572, 598, etc. If theres any engine out there , that can deal with a little extra duration, without such drastic side effects, its a big ci big block chevy. I've seen a few of them, with some cams that have alot of duration, idle very well, which shocked me .
I'm sure a 29ft'er with a single engine, might not want to trade off low speed torque. Lets say, a 29ft fountain with a single 540. He might need max torque down low, to get some good planing, and acceleration. He only has 650ft lbs available per say. Now, a twin engine 32 Fountain, with a pair of 540's in it? Install a pair of those same 540's in it, now he has 1300FT lbs on tap, in a hull that weighs a little more than that 29 single. That guy, could lose 50ft lbs a side, for a gain in upper rpm power, still have a boat that accelerates like a banshee, and screams at top speed as well.
I think that when a builder is building a combo, or a engine developer is spec'ing out a build, should consider the hull/application that the engines are going in, and focus on the actual performance of the boat, not just spec the perfect engine combo for the dyno. A big block chevelle that see's track only use, shouldnt get the same cam/heads, etc , as the one that gets to the track once a year, and 95% is going to car shows and ice cream parlors.
Just thinking out loud here.
Here is a quote from 500 yrs ago that still sticks with me, even though I have gone against it several timesfor what ever reason, but then it pops back in my head, and proves to be true most times.
John Lingenfelter - "It's almost impossible to out cam a BBC." This quote was when 496's -510's where king of the hill and GM was just introducing the 502 shortblocks. Obviously we have to take this quote in a little stride, but their is alot of truth to it.
09-21-2016, 08:02 AM
#253
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Thought so, more cam education since then has shown me otherwise, I thought at the time smaller cams would bring more tq later like my old ones, I am more educated now. That's the whole point of me "whining" God forbid I learn more by posting... Most of these threads really raise eyebrows yet some see it as "whining"
09-21-2016, 08:04 AM
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Thought so, more cam education since then has shown me otherwise, I thought at the time smaller cams would bring more tq later like my old ones, I am more educated now. That's the whole point of me "whining" God forbid I learn more by posting... Most of these threads really raise eyebrows yet some see it as "whining"
09-21-2016, 08:09 AM
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True, was hoping to get some long term success story's, yet to see that, nice to know I get to take apart good running engines to cerify they are ok when the goal was to leave them alone, guys can say I'm whining but whatever... You should not have to tear apart a Hyd. Roller engine that runs fine at 65 hours just to check things... If i was making 800 hp and maxed out that's different..
My cams are pretty similar to yours and my springs lost zero pounds after 80 hours of 4500-5000 rpm. I really doubt you are having problems. Its kind of silly to rule out a cam profile because someone broke a lifter. You have no idea what diameter/length pushrods he had, no idea how heavy his valves were etc. he could have been well into valve float and ran it without knowing. Thats why you check spring seat pressure every once in a while so you can make sure your valvetrain is happy or you need to try a few different things..... More spring, less spring, lighter retainers, bigger pushrods... Even maybe a new cam
09-21-2016, 08:09 AM
#257
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I have one eyebrow straight across wondering when its gonna stop, Helen Keller could of seen where this thread was heading, Mild, SB and a couple other's have posted good info, good luck...........BTW my B cam's worked great in my 540's
09-21-2016, 08:36 AM
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The port volume is determined by the length of the port and Cross-Sectional Area (CSA). Matching the correct CSA to the engine’s demand is the key. The properly sized intake runner will create the right balance between airflow volume and airflow velocity, and it’s not always the biggest runner that wins.
“We usually recommend the smallest port volume with the highest efficiency,” “This means there’s good velocity through the port and the ability to fill the cylinder.”
The article is below and has some good key points. This also hits on how you build an engine combination that is matched instead of simply throwing cams at it.
http://www.onallcylinders.com/2015/1...ylinder-heads/
“We usually recommend the smallest port volume with the highest efficiency,” “This means there’s good velocity through the port and the ability to fill the cylinder.”
The article is below and has some good key points. This also hits on how you build an engine combination that is matched instead of simply throwing cams at it.
http://www.onallcylinders.com/2015/1...ylinder-heads/
09-21-2016, 08:39 AM
#259
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One thing i will be doing from now on, and did on my current heads, is check each and every spring. Each spring was taken out of the box, and put in the spring tester. Seat pressure checked, open pressure checked, and coil bind checked.
Out of 32 springs, sure enough, found one spring way out of spec.
If i was tim, if the springs check out ok, valves are sealing well, and visually things look fine, id prob leave the engines in, cover the boat, and save money for next seasons fuel fund.
When the engines get tired, yank em, then make some changes to the combo. Or, if you have valve leaking, or signs of valvetrain issues, yank them now. You certainly dont want to deal with any more failures that hurt the hard parts.
The area that a few builders using bobs cams and heads, had in common, were the exhaust valve seats being pounded into the head, and lobe wear issues. Pretty sure there were a couple broken scorpion rockers in there as well.
Really chitty part of that story was, even though a few of these builders, experienced the exact same issues as the others, when it was brought to bobs attention, he acted as if he had never heard of that happening. There was alot of tjme and money wasted at the builders expense, rather than trying to get together as a group, and find out WHY it was happening. If you were the builder, you'd be prettt pizzed when you find out others were having the same issues, and it was swept under the rug.
Out of 32 springs, sure enough, found one spring way out of spec.
If i was tim, if the springs check out ok, valves are sealing well, and visually things look fine, id prob leave the engines in, cover the boat, and save money for next seasons fuel fund.
When the engines get tired, yank em, then make some changes to the combo. Or, if you have valve leaking, or signs of valvetrain issues, yank them now. You certainly dont want to deal with any more failures that hurt the hard parts.
The area that a few builders using bobs cams and heads, had in common, were the exhaust valve seats being pounded into the head, and lobe wear issues. Pretty sure there were a couple broken scorpion rockers in there as well.
Really chitty part of that story was, even though a few of these builders, experienced the exact same issues as the others, when it was brought to bobs attention, he acted as if he had never heard of that happening. There was alot of tjme and money wasted at the builders expense, rather than trying to get together as a group, and find out WHY it was happening. If you were the builder, you'd be prettt pizzed when you find out others were having the same issues, and it was swept under the rug.
09-21-2016, 08:45 AM
#260
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First of all of you don't like it, don't read it...
Second, where have I said no info was posted? Or where did I say I would not touch it, change or look at things?
Some of you people spend so much time trying to make me look bad and not help, just say this crap... Where's your input? Zero.
Second, where have I said no info was posted? Or where did I say I would not touch it, change or look at things?
Some of you people spend so much time trying to make me look bad and not help, just say this crap... Where's your input? Zero.
