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Stamped Steel vs. Roller Rockers - Test Data Please!

General engine tech -- Drag Racing to Circle Track

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Procision-Auto
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Stamped Steel vs. Roller Rockers - Test Data Please!

Post by Procision-Auto »

.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):

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Post by beth »

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.


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Post by Racer Roy »

One of the mags - either Circle Track or Stock Car - just had a rocker comparo test. The aluminum rollers made the most power on their test mule.
The stamped steel rockers burnt up as the spring loads were too much for the pivot balls.

RR
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Post by MadBill »

Current Circle Track.
Felix, qui potuit rerum cognscere causas.

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Post by Procision-Auto »

I don't suppose I'll get free info from the magazine, but for those that
have read the article was there a worthy HP increase across the band,
or from mid band to peak HP?

If I may ask as well, what was the percentage of power increase at peak RPM?

Thank you.
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Post by Ed Wright »

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.
Last edited by Ed Wright on Thu Jan 11, 2007 1:07 pm, edited 1 time in total.
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stock rockers

Post by bigjoe1 »

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

Post by Wolfplace »

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.
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Post by Procision-Auto »

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?
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Post by randy331 »

Bigjoe;

You said that 1.6 in, 1.5 ex. rockers would make more power than 1.6 in, 1.6 ex. rockers.

Does that also hold true on cam-limited, or stock-camed engines? Or is that mainly true on engines with closer to optimum size cam?

Thanks, Randy
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Post by Ed-vancedEngines »

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?

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Post by Wolfplace »

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.
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Post by MadBill »

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

Post by bigjoe1 »

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
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Track Tested - Rollers vs. Pressed Rocker Arms

Post by Hardcore »

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
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