Stamped Steel vs. Roller Rockers - Test Data Please!
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Stamped Steel vs. Roller Rockers - Test Data Please!
.I'm looking for back to back test data on engines using stamped steel
rockers and roller rockers (roller trunnion mainly).
I know many of you have access to dyno's and some well documented
test results and that's why I come here for information.
Personally, I have made the switch and noticed improvements, yet I am
not able to quantify my results...and that's a "no-no" in internet land!
Aside from the obvious reduced friction, improved BSFC, higher RPM
staiblity and rigidity of the design itself, I'd like to see your before/after
results when switching.
Thanks for your time and shared info.
These would be the types of rockers in question (but not limited to for this
discussion):
rockers and roller rockers (roller trunnion mainly).
I know many of you have access to dyno's and some well documented
test results and that's why I come here for information.
Personally, I have made the switch and noticed improvements, yet I am
not able to quantify my results...and that's a "no-no" in internet land!
Aside from the obvious reduced friction, improved BSFC, higher RPM
staiblity and rigidity of the design itself, I'd like to see your before/after
results when switching.
Thanks for your time and shared info.
These would be the types of rockers in question (but not limited to for this
discussion):
I don't have the answer you are looking for but do have some information that is related. The ratio of slotted stamped rockers changes with push rod length and hyd lifter preload. The more preload and shorter the pushrod the lower the ratio. As preload is lessened and push rods are lengthened the net lift goes up. The difference in lift can easily be measured and the difference affects power output.
beth
beth
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I'm sure spring pressure has something to do with any gains, very high spring pressure would possibly show more of a gain. I changed frrom stock rockers to 1.6 Comp stainless roller rockers on a stock LT1 of mine. Ran it on the dyno with stock rockers, and without moving the car from the dyno swapped rockers. Saw allmost 4 rwhp from the swap that is averaging four pulls with each, and monitoring oil, air and coolant temps.
About $350.00 for about 3 1/2 rwhp. $100.00 per rwhp. Hard to tell one week to the next, but it ran exactly the same times at the track both ways, one week apart.
About $350.00 for about 3 1/2 rwhp. $100.00 per rwhp. Hard to tell one week to the next, but it ran exactly the same times at the track both ways, one week apart.
Last edited by Ed Wright on Thu Jan 11, 2007 1:07 pm, edited 1 time in total.
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stock rockers
I have been testing with an engine dyno for 30 some years. This is one of the most common and easy things to test on the dyno. When you go from the stock ratio to a higher ratio alu or steel aftermarket rocker. it usually makes a small increase at high RPM only. The lower the power level is, the less you can gain. Example.350 HP engine, 1.6 rockers make 7 oe 8 HP gain at 5000 RPM, at 6000 it might go up to 13-15 gain. Just to put on roller rockers with the same ratio does little or nothing (3 or 5 HP)Many times 1.6 0n both valves is worth little or nothing (5 or 7 HP) 1.6 intake and 1.5 ex might be worth 15 to 17 bHP. Those COmp cams things with the stock ball(NOT A REAL SOLLER BEARING0 are worth nothing unless you increase the lift with more ratio. JOE SHERMAN RACING
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Re: stock rockers
=bigjoe1 wrote:I have been testing with an engine dyno for 30 some years. This is one of the most common and easy things to test on the dyno. When you go from the stock ratio to a higher ratio alu or steel aftermarket rocker. it usually makes a small increase at high RPM only. The lower the power level is, the less you can gain. Example.350 HP engine, 1.6 rockers make 7 oe 8 HP gain at 5000 RPM, at 6000 it might go up to 13-15 gain. Just to put on roller rockers with the same ratio does little or nothing (3 or 5 HP)Many times 1.6 0n both valves is worth little or nothing (5 or 7 HP) 1.6 intake and 1.5 ex might be worth 15 to 17 bHP. Those COmp cams things with the stock ball(NOT A REAL SOLLER BEARING0 are worth nothing unless you increase the lift with more ratio. JOE SHERMAN RACING
And for what it is worth, I personally hate those Comp rockers with the roller tip & ball
I have had more issues with those than I ever had with stock GM rockers.
Mike
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Thank you for that very informative angle.
Although 3-5HP/350 HP may seem like very little, to me it's a big step...especially
if that is an average gain over a spectrum of RPM.
The ability to increase power over a window of 2000 RPM in the upper
register is cool beans - especially if the motor is spinning 6000+ RPM.
Aside from the other benefits already mentioned, isn't it also true that
as lift increases, the ability of the stamped rocker to follow the cam
lobe profile becomes more difficult?
Although 3-5HP/350 HP may seem like very little, to me it's a big step...especially
if that is an average gain over a spectrum of RPM.
The ability to increase power over a window of 2000 RPM in the upper
register is cool beans - especially if the motor is spinning 6000+ RPM.
Aside from the other benefits already mentioned, isn't it also true that
as lift increases, the ability of the stamped rocker to follow the cam
lobe profile becomes more difficult?
Joe,
Have you considered that possibly the noted power increase with the larger ratio rocker just might not be as much becuase of the increased lift but maybe more so becuase by increasing rocker ration it is in effect getting valve off the seat sooner and faster as well as an increase in actual effective duration?
Also isn't it possible that in those you tested the exhaust was already closely matched to the exhaust port potential, so an increase of ratio would have been detrimental becuase of opening the exhaust valve sooner and wasting after TDC cylinder pressure on the power stroke. as well as maybe causing an over scavagening during blow down?
Ed
Have you considered that possibly the noted power increase with the larger ratio rocker just might not be as much becuase of the increased lift but maybe more so becuase by increasing rocker ration it is in effect getting valve off the seat sooner and faster as well as an increase in actual effective duration?
Also isn't it possible that in those you tested the exhaust was already closely matched to the exhaust port potential, so an increase of ratio would have been detrimental becuase of opening the exhaust valve sooner and wasting after TDC cylinder pressure on the power stroke. as well as maybe causing an over scavagening during blow down?
Ed
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=Ed-vancedEngines wrote:Joe,
Have you considered that possibly the noted power increase with the larger ratio rocker just might not be as much becuase of the increased lift but maybe more so becuase by increasing rocker ration it is in effect getting valve off the seat sooner and faster as well as an increase in actual effective duration?
Also isn't it possible that in those you tested the exhaust was already closely matched to the exhaust port potential, so an increase of ratio would have been detrimental becuase of opening the exhaust valve sooner and wasting after TDC cylinder pressure on the power stroke. as well as maybe causing an over scavagening during blow down?
Ed
Increasing the rocker ratio does not change seat to seat timing assuming you adjust lash accordingly
It will in effect change the duration everywhere else very slightly but the biggest effect is in lift.
Mike
Lewis Racing Engines
4axis CNC block machining
A few of the cars I have driven & owned
A tour of my shop
The Dyno
And a few pics of the gang
"Life is tough. Life is even tougher if you're stupid"
John Wayne
Lewis Racing Engines
4axis CNC block machining
A few of the cars I have driven & owned
A tour of my shop
The Dyno
And a few pics of the gang
"Life is tough. Life is even tougher if you're stupid"
John Wayne
A number of years ago I was helping a guy dyno his stock 305 TPI Chev engine. He wanted to try 1.6 rockers, and I convinced him to do them 8 at a time. The intakes netted 12 HP at the top end (~5,000 RPM), the exhaust gave +/- 1 everywhere... (stock lift was ~ 0.450")
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rocker ratios
It is true, a stock or a mild cam is more likely to want the higher ratio rockers. Most engines do NOT respond to more exhaust valve lift with race type camshafts, duration, yes, lift no. Just my experience. JOE SHERMAN RACING
Track Tested - Rollers vs. Pressed Rocker Arms
To answer the original question. Got involved directly with this testing.
Recently, this past fall, had an opportunity at the track to test a true Chevelle LS-6. Some 3 runs made back to back with the roller rockers installed, car ran 12.6's at 110/111/110 mph.
Changed to pressed G.M. with slotted balls and oem style locknuts, same number of runs, 3, car ran 12.6's again but picked up 1-2 mph to 112/111/112. Would say rocker's don't matter. Roller's will most likely outlast the pressed ones, maybe, and valve train component's will generally see less wear as well with the rollers. MPH was probably due to temps later in the day.
Spring pressure on solid lifter cam at 140 closed, 350 open at about .560" net lift. Through the traps at 6500+. No float up to 7000!
Bill
Recently, this past fall, had an opportunity at the track to test a true Chevelle LS-6. Some 3 runs made back to back with the roller rockers installed, car ran 12.6's at 110/111/110 mph.
Changed to pressed G.M. with slotted balls and oem style locknuts, same number of runs, 3, car ran 12.6's again but picked up 1-2 mph to 112/111/112. Would say rocker's don't matter. Roller's will most likely outlast the pressed ones, maybe, and valve train component's will generally see less wear as well with the rollers. MPH was probably due to temps later in the day.
Spring pressure on solid lifter cam at 140 closed, 350 open at about .560" net lift. Through the traps at 6500+. No float up to 7000!
Bill