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-   -   Roller Rockers vs stock.. (http://www.hotrodders.com/forum/roller-rockers-vs-stock-176889.html)

_titan_ 04-25-2010 06:41 PM

Roller Rockers vs stock..
 
I'm pretty much a noob when it comes to push rod motors, this 350sb is the first push rod i've rebuilt, or attempted to rebuild, everything else has all been ohc motors. So this is a noob question from me. I have used the search button and read a bunch of threads but no real answer to my question. What is the Benefit of running roller rockers as opposed to the stock stamped rocker arms? I understand you are using a roller fulcrum as opposed to a ball and stamped steel and this reduces friction, but is there any real benefit other then a reduction of friction? is there any slight hp gain out of this? any reliability or longevity gain?
take me to school guys..
I'm looking at getting a set of 1.6:1 full roller rockers

matts37chev 04-25-2010 06:47 PM

i think most guys switch because the stock stamped steel rockers dont have a long enough slot for high lift cam
then they figure every little bit helps on freeing up HP

Blazin72 04-25-2010 07:38 PM

Hmmm, another member from Shelton. What are the odds? I am guessing your first name is Matt too? Interesting coincidence....

techinspector1 04-25-2010 08:27 PM

Quote:

Originally Posted by titan uranus
What is the Benefit of running roller rockers as opposed to the stock stamped rocker arms? is there any slight hp gain out of this?
I'm looking at getting a set of 1.6:1 full roller rockers

First off, and this is just my personal take on the ratio question. I will use increased ratio rockers only on a solid or hydraulic roller tappet motor. A flat tappet cam is already running in a gray area in my opinion. To increase the load between the lifter and the cam lobe on a flat tappet cam is foolish, particularly with an "extreme" grind.

I have seen claims of 20-30 hp with roller rockers over conventional stamped rockers, but have never seen proof of it. It does make sense to me that you would free-up some power. Something else that makes sense to me is the claim that roller rockers will lower oil operating temperatures due to reduced friction.

And for what it's worth, I consider Harland Sharp to be the finest roller rocker on the market.

oldbogie 04-26-2010 12:32 PM

Quote:

Originally Posted by titan uranus
I'm pretty much a noob when it comes to push rod motors, this 350sb is the first push rod i've rebuilt, or attempted to rebuild, everything else has all been ohc motors. So this is a noob question from me. I have used the search button and read a bunch of threads but no real answer to my question. What is the Benefit of running roller rockers as opposed to the stock stamped rocker arms? I understand you are using a roller fulcrum as opposed to a ball and stamped steel and this reduces friction, but is there any real benefit other then a reduction of friction? is there any slight hp gain out of this? any reliability or longevity gain?
take me to school guys..
I'm looking at getting a set of 1.6:1 full roller rockers

From the factory the 350 uses a 1.5 to 1 ratio rocker, the LT4 excepted at 1.6 to 1. There is power to gained switching from a 1.5 to a 1.6 whether or not the change includes roller bearing or not. The 6+ percent in rocker ratio changes the peaks for torque and horsepower by about 6 percent and moves those peaks about 6% higher in the RPM band. Imagine that. But one for one on ratio the power difference between a ball and socket rocker and a roller isn't outside the range of the variance you see in an engine from one dyno run to the next with the same setup, a couple,,,three horses one way or the other.

Where the difference between identical ratios but roller versus ball/socket does show up is reliability over 6000 RPM. When the revs get up here you just can't get enough lubrication onto the ball and socket to control the heat. The more aggressive the lift against duration and the stronger the valve spring pressure when combined with high RPMs the sooner this hits the wall. So the top end power and the time you can keep the engine there will be limited by the inevitable heat failure of these parts. A rocker with a roller trunnion gets simply, though not cheaply, around this problem.

Many rockers come with roller tip, including those intended for lower RPM operation by virtue of the ball and socket pivot. This is intended to trade the non roller's scraping action on the valve stem tip for a rolling action. This should reduce stem and guide wear by reducing the side to side pull and push of the sliding motion between rocker and tip for a rolling contact. This is more critical with lots of lift and high pressure springs. My own rules are roller tips get used when the lift gets above .47 inch. The other advantage I see is that it's easier to set them up where the motion on the stem tip can be kept as close as possible about the centerline of the stem such that off center loads that will result in stem and guide wear can be minimized. The rollers not generating anything like the heat of the ball and socket design allows the upper end lubrication to be used to cool the valve springs. Many race only engines reduce the push rod oil feed since the roller doesn't need much and they install a spray bar on the valve springs for cooling them.

Another advantage is many brands of roller rockers are serviceable with new bearings and trunnions which is certainly more cost advantageous than having to scrap entire rockers when replacement of these parts becomes necessary.

The biggest downside of roller rockers is that a failure puts shrapnel into the oily side of the motor. This possibility drives us to screens at the return drains and strong magnets positioned in the heads and valley to stop the migration of failed roller bearing parts into the oil sump. For this reason it's smart to purchase quality rockers.

So in the end on a one for one ratio trade, rollers don't make any power. When going from a 1.5 to a 1.6, there is about a 6 percent overall power gain and that will also be about 6 percent further up the RPM band and it tends to broaden the top power a bit which is to say the engine will hang onto the power peak longer. Wear in the stem to guide interface is reduced when using high lifts. But if these things come apart they make one hell of a mess if the wreckage isn't contained.

Bogie

_titan_ 04-26-2010 12:39 PM

So basically for my application where i need all the power lower in the rpm range and its not going to be seing much of anything over 4800rpm I'm best to just stick with the stock stamped ball/socket rockers with the 1.5 ratio

oldbogie 04-26-2010 01:27 PM

Quote:

Originally Posted by titan uranus
So basically for my application where i need all the power lower in the rpm range and its not going to be seing much of anything over 4800rpm I'm best to just stick with the stock stamped ball/socket rockers with the 1.5 ratio

I'd have to say "yes" conventional 1.5s would be the way to go in this case. Not only that, if bottom end grunt is what you need, I'd opt for Swirl Port heads over Vortecs. Now watch the mail fly.

Bogie

techinspector1 04-26-2010 02:04 PM

I would only add that with a stock OEM stamped rocker arm,you may get less than the design ratio. I've heard of 1.5 Chevy rockers being tested as low as 1.45:1. So, if for no other reason than getting the full design lift from the camshaft you will use, aftermarket roller rockers make sense to me.

wyomingoutlaw 04-27-2010 01:55 AM

I just want to throw this out there; I was running aluminum roller rocker arms and had one break on my pontiac. it bent the valve preventing it from closing all the way, piston slammed into it and took a chunk out of the top of the piston. a lot of time and money later I got it all back together, but now I'm running comp cams magnum rocker arms. they are roller rockers but made of steel. first race is about a month away but I don't expect them to break.

I just can't see running an aluminum part on something that sees so much stress. I guess I did it, but never again...

a1supersport 04-27-2010 05:01 AM

Quote:

Originally Posted by wyomingoutlaw
I just want to throw this out there; I was running aluminum roller rocker arms and had one break on my pontiac. it bent the valve preventing it from closing all the way, piston slammed into it and took a chunk out of the top of the piston. a lot of time and money later I got it all back together, but now I'm running comp cams magnum rocker arms. they are roller rockers but made of steel. first race is about a month away but I don't expect them to break.

I just can't see running an aluminum part on something that sees so much stress. I guess I did it, but never again...

Ahhh, happened to you too? A friend of mine broke a Harland Sharp rocker and was lucky it broke the way it did...no damage to the engine. From then on I either used stamped-steel (daily driver), or stainless-steel rollers (1/4 mile). Stainless steel was overkill, and pricey, but worth it...for peace-of-mind I guess...

Uncle Buck 08-31-2010 04:26 PM

Paging Bogie....
 
Quote:

Originally Posted by oldbogie
Not only that, if bottom end grunt is what you need, I'd opt for Swirl Port heads over Vortecs. Now watch the mail fly.

Bogie

Sorry for pulling up a six month old thread, but I have to ask Bogie to explain this.

I'm rebuilding a carburated 327 that will never see 4,500 RPMs for use in a 4x4 with 4:11 gearing and 33" tires. I've been studying the difference between the 193 and Vortec heads, and had just about decided to go with Vortecs after I read one of Bogie's posts over on the old Sallee Chevrolet board, where he said that the Vortec heads where only 5 or so ft/lbs behind the swirl port heads down low.

Bogie, if you see that can you please explain why you would chose swirl port heads over Vortecs if I'm looking for "bottom end grunt" (and that's exactly what I'm looking for!)

oldbogie 08-31-2010 05:04 PM

Quote:

Originally Posted by Uncle Buck
Sorry for pulling up a six month old thread, but I have to ask Bogie to explain this.

I'm rebuilding a carburated 327 that will never see 4,500 RPMs for use in a 4x4 with 4:11 gearing and 33" tires. I've been studying the difference between the 193 and Vortec heads, and had just about decided to go with Vortecs after I read one of Bogie's posts over on the old Sallee Chevrolet board, where he said that the Vortec heads where only 5 or so ft/lbs behind the swirl port heads down low.

Bogie, if you see that can you please explain why you would chose swirl port heads over Vortecs if I'm looking for "bottom end grunt" (and that's exactly what I'm looking for!)

Good grief that's a long time ago!

Where I'm at with an engine that wouldn't be revved over 4500 RPM is that Swirl Ports at that level are working right where they were designed for. They will pick up the bottom end a small amount 5 or so ft pounds, which is really incidental compared to Vortecs, but they support your wallet well. If you move the Vortecs you really need a Vortec specific intake which is a bit pricey. Additionally, if you need to run emissions the EGR on the Vortec set up is external and requires a bunch of plumbing which can range from some GM and Edlebrock parts ranging from a Vortec exhaust manifold or header and external plumbing to modifying what you've got for an exhaust manifold or header and fabricating the external plumbing; all depending on your capabilities. So there is a considerable cost advantage to not using the Vortec head on a slow turning engine as you're not going to rev it where you can capitalize on the upper end power advantage.

So I'm mostly at a cost versus gain isn't worth it because you're incurring the cost and not using the gain. If you want to raise the RPMs with a bigger cam and possibly some head work, then the answer changes as the revs get over 4000.


Bogie

Uncle Buck 08-31-2010 06:30 PM

Quote:

Originally Posted by oldbogie
Good grief that's a long time ago!

Where I'm at with an engine that wouldn't be revved over 4500 RPM is that Swirl Ports at that level are working right where they were designed for. They will pick up the bottom end a small amount 5 or so ft pounds, which is really incidental compared to Vortecs, but they support your wallet well. If you move the Vortecs you really need a Vortec specific intake which is a bit pricey. Additionally, if you need to run emissions the EGR on the Vortec set up is external and requires a bunch of plumbing which can range from some GM and Edlebrock parts ranging from a Vortec exhaust manifold or header and external plumbing to modifying what you've got for an exhaust manifold or header and fabricating the external plumbing; all depending on your capabilities. So there is a considerable cost advantage to not using the Vortec head on a slow turning engine as you're not going to rev it where you can capitalize on the upper end power advantage.

So I'm mostly at a cost versus gain isn't worth it because you're incurring the cost and not using the gain. If you want to raise the RPMs with a bigger cam and possibly some head work, then the answer changes as the revs get over 4000.


Bogie

Thanks for the quick response and straight answer (mainly the straight answer, as they can be hard to come by on some forums!)

FWIW I'm not running EGR and I was planning on a new dual plane manifold already, to replace the 30 year old Offy dual port I have now, so cost is pretty much a wash. Sounds like that would move the advantage to the Vortec heads since they're a little more compression tolerant (which should give me that 5 ft/lbs of torque!).

Thanks again!

oldbogie 08-31-2010 07:12 PM

Quote:

Originally Posted by Uncle Buck
Thanks for the quick response and straight answer (mainly the straight answer, as they can be hard to come by on some forums!)

FWIW I'm not running EGR and I was planning on a new dual plane manifold already, to replace the 30 year old Offy dual port I have now, so cost is pretty much a wash. Sounds like that would move the advantage to the Vortec heads since they're a little more compression tolerant (which should give me that 5 ft/lbs of torque!).

Thanks again!

Sounds like a solution to me.

An Offy Dual Port, here I though I was the only person to purchase one of those.

Bogie

PS you got me to thinking. I never, nor have I read about, a head swap to Vortecs that also included a piston swap to idealize the squish and quench characteristics of the Vortec head. It's always been a Vortec head strapped to whatever bottom end was already there whether the pistons had round dishes or not before and after. So your comment on greater compression tolerance got me thinking that I need to build a stock Chevy small block with those round dish pistons and pre Vortec heads, then put Vortec heads on it and redo the dyno run, this is what we usually see for data. Then take the engine apart and put D dish or flat top pistons in it, idealize the deck clearance to run the compression up and maximize the squish/quench of the head taking the SCR to the tolerance limit of the existing timing to see how far the SCR can be pushed before the chamber pings. Then test to see if the usually seen lost bottom end torque of these heads is recovered while the top end gains are either improved or at lest not compromised. I've never done it quite that way in back to back tests nor have I seen it done. hummmm!

Bogie

Duntov 08-31-2010 07:51 PM

Harland Sharp
 
Quote:

Originally Posted by techinspector1
I would only add that with a stock OEM stamped rocker arm,you may get less than the design ratio. I've heard of 1.5 Chevy rockers being tested as low as 1.45:1. So, if for no other reason than getting the full design lift from the camshaft you will use, aftermarket roller rockers make sense to me.

TI said it. That's why roller and that's why Harland Sharp. Reduce friction and improve geometry. You still have the 1.5 option, and don't underestimate the advantages of reduced friction and oil temp. We've noticed and or had customers comment on the improved performance many times.
I've noted the idle rpm before/after replacement of stamped with roller and with the same ratio it almost always increases the idle rpm at least some. Often people claim smoother through out the RPM band. It's easier on pressed in studs also.


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