Cam and valvetrain longevity....??? low duration high lift...
09-19-2016, 09:57 PM
#191
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Might be making exhaust changes not cams!! Or both lol
Tim posted a question on facebook, asking if anyone ever dynoed with dry race style dyno headers, vs wet marine exhaust back to back. A guy replied with these sheets. His "wet" exhaust, was stainless marine wet manifolds.
At 3500RPM, the wet exhaust gave up 36 ft lbs of torque.
At 5100RPM, the wet exhaust gave up 39 horsepower.
For some reason, we argue over 10cc on intake runner volumes, 1/2 point of static compression, a couple degrees of cam duration, 100cfm of carb airflow. Everyone is so scared to add duration to a camshaft, worried that it will lose too much torque down low. Everyone is scared to be a few cc to large on an intake runner, fearing a loss of torque. We'll spend thousands on CNC ported heads, custom roller cams, and all kinds of stuff to make more HP and torque. But when the exhaust subject comes up, there's crickets. Seems like everyone has the mindset, that headers and good exhaust, is only for top end power. For the past 50 years, one of the best , simplest, and most effective mods, to almost any hot engine, heck, even a 454 in a motorhome, was a set of free flowing headers, and see torque gains.
I've seen quite a few engines come off the dyno, and need major jet changes, because the engines were installed with wet exhaust manifolds, when they were originally tuned on the dyno with 2.25 ID race car headers. Just water in the pipes alone, can be a big restriction. The average marine manifold has 3.5" inner pipe. Then you dump huge volume of water in that 3.5" pipe, and that pipe diameter becomes even smaller, as well as the water hindering airflow. I really don't see a good reason these days, to be running a wet performance exhaust. There's plenty of sound solutions that can keep the noise down. Not only is wet exhaust a hinderance on power, its also the limiting factor on camshaft choice. My tails are dry until the end. I have gaffrig air operated mufflers on them. At idle, theres water dumping into the muffler, and even with the mufflers open, its not too loud. Close them, and my 800hp engines sound like 330's with wet merc exhaust. At WOT, I have about 4 inches of the 4.5" pipe where water is entering. Basically, the back half of the mufflers see water. They don't get hot.
I think we should line up a few exhaust systems, and use full forces engines as test mules.
At 3500RPM, the wet exhaust gave up 36 ft lbs of torque.
At 5100RPM, the wet exhaust gave up 39 horsepower.
For some reason, we argue over 10cc on intake runner volumes, 1/2 point of static compression, a couple degrees of cam duration, 100cfm of carb airflow. Everyone is so scared to add duration to a camshaft, worried that it will lose too much torque down low. Everyone is scared to be a few cc to large on an intake runner, fearing a loss of torque. We'll spend thousands on CNC ported heads, custom roller cams, and all kinds of stuff to make more HP and torque. But when the exhaust subject comes up, there's crickets. Seems like everyone has the mindset, that headers and good exhaust, is only for top end power. For the past 50 years, one of the best , simplest, and most effective mods, to almost any hot engine, heck, even a 454 in a motorhome, was a set of free flowing headers, and see torque gains.
I've seen quite a few engines come off the dyno, and need major jet changes, because the engines were installed with wet exhaust manifolds, when they were originally tuned on the dyno with 2.25 ID race car headers. Just water in the pipes alone, can be a big restriction. The average marine manifold has 3.5" inner pipe. Then you dump huge volume of water in that 3.5" pipe, and that pipe diameter becomes even smaller, as well as the water hindering airflow. I really don't see a good reason these days, to be running a wet performance exhaust. There's plenty of sound solutions that can keep the noise down. Not only is wet exhaust a hinderance on power, its also the limiting factor on camshaft choice. My tails are dry until the end. I have gaffrig air operated mufflers on them. At idle, theres water dumping into the muffler, and even with the mufflers open, its not too loud. Close them, and my 800hp engines sound like 330's with wet merc exhaust. At WOT, I have about 4 inches of the 4.5" pipe where water is entering. Basically, the back half of the mufflers see water. They don't get hot.
I think we should line up a few exhaust systems, and use full forces engines as test mules.
09-19-2016, 10:39 PM
#193
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Unless your going to spend $7k on two sets of Eickert Headers your wasting your money on the exhaust. SM will never scavenge and by losing the little bit of water you have in your exhaust over the last 6-7" by going dry isn't going to do squat for your speed. For comparison I went from SM manifolds with standard tails to Eickerts and gained 2 mph in a light boat. Your boat weighs 3x my little formula 242 with a little over 2 times the power. Your boat is going to take a lot of additional power to see even 1 mph. SB please chime in here if I'm wrong- but you need to be spinning upwards to 5700 rpms to start getting the benefits of scavenging from the exhaust. Lets say you gain 40 hp per side with the best exhaust. I'm willing to bet you would be lucky to see 1 MAYBE 2 mph with that amount of gain. You seem he!! bent on going faster, which all of us here are in the same group, but I think at this point it would be cheaper to buy a faster hull and put your engines in it. Trying to make this heavy cig go faster is going to drive you insane and in the poor house.
09-19-2016, 11:30 PM
#194
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Getherdone I had a drink everytime you said 5800 in his thread and now I`m wasted!!! way to go.. hey I heard your dyno guy has some kind wheel of fortune readout for tq and hp? Got any pics of that space aged set up? Do you have to camcorder that instead of a typical read out? I bet it`s BETA still or did they upgrade to VHS? Would love to see it. Maybe it`s more like a carnival set up, when you hit a certain hp number on the big wheel you walk away with a stuffed toy! it`s consistently 20-50 teddybears low thou so you gotta account for that.
5800!!!!!
5800!!!!!
09-20-2016, 05:19 AM
#195
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I am hell bent to see some sort of gain over my old engines, and maximizing what these are, if I wanted to be super fast I would have a stepped hull, that's got nothing to do with the situation over maximizing my current setup, making sure it's right, and all that it can be, if I was that concerned about speed then I would just boost it and get it, would not cost that much... You go spend 35,000.00 to go slower and let's see what you do to at least be as good as you were before... It's not fun.
Unless your going to spend $7k on two sets of Eickert Headers your wasting your money on the exhaust. SM will never scavenge and by losing the little bit of water you have in your exhaust over the last 6-7" by going dry isn't going to do squat for your speed. For comparison I went from SM manifolds with standard tails to Eickerts and gained 2 mph in a light boat. Your boat weighs 3x my little formula 242 with a little over 2 times the power. Your boat is going to take a lot of additional power to see even 1 mph. SB please chime in here if I'm wrong- but you need to be spinning upwards to 5700 rpms to start getting the benefits of scavenging from the exhaust. Lets say you gain 40 hp per side with the best exhaust. I'm willing to bet you would be lucky to see 1 MAYBE 2 mph with that amount of gain. You seem he!! bent on going faster, which all of us here are in the same group, but I think at this point it would be cheaper to buy a faster hull and put your engines in it. Trying to make this heavy cig go faster is going to drive you insane and in the poor house.
09-20-2016, 06:41 AM
#196
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You don't just have a pulse of exhaust gas (150 ft/sec - 300 ft/sec) at a certain volume exiting the exhaust port,you also have an energy wave (1,300 - 1,700 feet per second) that is created from the rapidly expanding combustion gases.
Also remember, peak cylinder combustion pressures are usually at peak torque rpm.
Also remember #2, you have several things that happen when the combustion gases are expelled during the exhaust event. When the exhaust valve opens you have a bunch of cyl pressure that will start the evacuation (piston is going towards bdc - we call this period pressure decay) and then the remaining exhaust gas will be pumped out as the piston comes up to TDC. The more exhaust that is in the cylinder at this period will create what we call pumping loss. ie: energy used to push this out.
That is basics...there is a ton of this info available from super basics to way over our heads, and then some theories as it is still not totally understood to this day, but obviously we are a lot closer. What we do know can influence our power big time +/- , therefore we should not turn a blind eye to it.
Lastly for this post, to sound like a broken record but to keep hammering this home, the more valve overlap a NA engine has, the more important it is to have an exhaust system that is tuned to the motor.
Last edited by SB; 09-20-2016 at 07:02 AM.
09-20-2016, 06:46 AM
#197
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Was a metering block Holley had that let you change 'jets' without puliing carb apart.
Weber also came out with 'Power Plates' , I believe they where called , many years ago also that let you do the same, but with turns of screws....basically like how the idle screws work. Turn in to restrict fuel flow and out for more.
I don't believe wither are available any more but i could be wrong.
Weber also came out with 'Power Plates' , I believe they where called , many years ago also that let you do the same, but with turns of screws....basically like how the idle screws work. Turn in to restrict fuel flow and out for more.
I don't believe wither are available any more but i could be wrong.
09-20-2016, 06:51 AM
#198
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I just spend 30K and I gained 10+ mph over my last set up. But I added 55 C.I per engine, boxes and shorter drives.
09-20-2016, 07:03 AM
#199
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Because Bob told me 700 hp would be not hard to see, and gain me 100 more HP per engine over my old engines... Average mph loss is at least 1.5 so far..
I have labbed props no change is speed at WOT gained a lot at cruise... Hard to gain speed up top when engines make 5 hp more over a 400 rpm spread.
I have labbed props no change is speed at WOT gained a lot at cruise... Hard to gain speed up top when engines make 5 hp more over a 400 rpm spread.
09-20-2016, 07:03 AM
#200
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Gotcha, jet changes are super easy so no big deal lol I'm used to wrenching !!
Was a metering block Holley had that let you change 'jets' without puliing carb apart.
Weber also came out with 'Power Plates' , I believe they where called , many years ago also that let you do the same, but with turns of screws....basically like how the idle screws work. Turn in to restrict fuel flow and out for more.
I don't believe wither are available any more but i could be wrong.
Weber also came out with 'Power Plates' , I believe they where called , many years ago also that let you do the same, but with turns of screws....basically like how the idle screws work. Turn in to restrict fuel flow and out for more.
I don't believe wither are available any more but i could be wrong.
