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helrazr3 01-23-2013 06:46 PM

roller rockers
 
hello, can someone tell me the difference between roller tip rockers and full roller rockers


thanks for your time.
rich

techinspector1 01-23-2013 07:01 PM

Quote:

Originally Posted by helrazr3 (Post 1638088)
hello, can someone tell me the difference between roller tip rockers and full roller rockers
thanks for your time.
rich

Hello Rich, well, I can tell you what I think, but it may not be the same answer that you will get from others.

Most of the heat and friction that is generated by the rocker arm is at the fulcrum, the sliding half-ball arrangement that has been used on Chevys since Ed Cole was a kid. Those fosdick rockers that Comp makes, the ones that use a sliding ball fulcrum and a roller tip are in my opinion, worthless as teets on a boar hog. Again, the heat and friction are in the fulcrum, not the tip. Now, if someone manufactured a rocker that used a roller fulcrum and a conventional tip, I'd recommend them. When properly set up, the rocker tip on a conventional stamped rocker does not slide on the valve tip, it rolls through a movement like the sole of your shoe does on the pavement. Think about it.

I have heard some guys claim a 20 hp improvement from using a roller fulcrum as compared to a sliding ball fulcrum, along with lower oil temps. I cannot confirm nor deny these claims.

I can confirm though, that the ratio of stock, stamped rockers is all over the place and all the ones I have checked have had ratios of less than 1.5:1. If you buy an aftermarket rocker, you will come closer to getting the ratio that is advertised. Scorpion rockers are good quality for the money. If you want the Cadillac of aluminum roller rockers, get a set of Harland Sharp rockers. If you want the best stainless steel stud-mounted roller rocker, pop for the Crower Enduro. Just my opinion, you understand.

Another point, rocker arms is not the place to try to save money on your build.....or any build.

Richiehd 01-23-2013 07:12 PM

I had a set of those Comp roller tips, and yes the fulcrums turned blue from heat. I am now using the Scorpion rockers, made in USA and reasonably priced. Nice quality. One thing Techinspector didnt tell you is the much better accuracy between pieces a roller rocker offers. A stamped steel rocker that is a 1.5 ratio can very greatly to be much less or much more than 1.50 We used to be retricted to stamped rockers in the class we ran, and we would go through buckets of rockers to find 16 with the highest ratios.
(Ok so T/I added that after I read it) Thanks

techinspector1 01-23-2013 07:22 PM

Quote:

Originally Posted by Richiehd (Post 1638100)
I had a set of those Comp roller tips, and yes the fulcrums turned blue from heat.

Those damned things should be against the law and Comp should be ashamed of themselves for deceiving these young kids with them. In my eyes, it's out and out fraud.

Richiehd 01-23-2013 07:29 PM

Quote:

Originally Posted by techinspector1 (Post 1638103)
Those damned things should be against the law and Comp should be ashamed of themselves for deceiving these young kids with them. In my eyes, it's out and out fraud.

I used them because they were advertised 1.52 ratio. Never noticed any performance difference one way or the other

helrazr3 01-23-2013 09:00 PM

thanks guys i get it now i've never used a roller cam before and i'm going back and forth with a tech guy from comp. about upgrading to a roller cam after catastrophic oil pressure failure in my 327 im being told by the machinist that it was from a lack of zinc in the oil :confused: :( but im not sure i buy that :pain: i had a comp cam and it was not part of the problem i have a separate thread for the motor

so i'm going to upgrade to a roller cam and im just trying to figure out what i need to do.

Richiehd 01-24-2013 05:29 AM

Just so you know, roller cam is different than roller rockers.

gearheadslife 01-24-2013 05:56 AM

Quote:

Originally Posted by techinspector1 (Post 1638103)
Those damned things should be against the law and Comp should be ashamed of themselves for deceiving these young kids with them. In my eyes, it's out and out fraud.


sorry, don't agree.I do agree they are fluff junk, but I can't fault comp for marketing them,as the kinks would say. " give the people what they want"


the auto part field is chock full of parts that don't do as clained,
as the maker saw a need/WANT and said.. why the heck not..

as they say a fool and his money will soon part..

MouseFink 01-24-2013 08:25 AM

Quote:

Originally Posted by techinspector1 (Post 1638103)
Those damned things should be against the law and Comp should be ashamed of themselves for deceiving these young kids with them. In my eyes, it's out and out fraud.

My engine builder told me that 25 years ago when I was considering using roller tip rocker arms. That is when I used full roller rocker arms for the first time and incidentally, they were Harland Sharp.

High lift camshafts are required to use high spring loads and must use full roller rocker arms. The reason full roller rocker arms are required is because high spring pressure will smoke the ball fulcrums in the stamped steel rocker arms. They can seize due to lack of oil. The hotter running ball fulcrums also raise the oil temperature.

In the mid-1960s, GM introduced restricted lifter and rocker arm oiling for the SB Chevrolet 327 CI /365 HP FI engines and aftermarket cam grinders were producing more radical camshafts with higher valve lifts and recommended higher valve spring rates. Mr. Gasket introduced grooved rocker balls for the stamped steel rocker arms in order to supply additional oil to the rocker arm ball fulcrums. That helped to lube the rocker ball fulcrums as long as the spring load did not exceed 300 lb.

The reason people use "roller tip" rocker arms is because they are cheap and they do not require poly-locks..

Mertz 01-24-2013 09:17 AM

I used them on my 350 and will be installing them on my 283 bacause I was told they are more accurate in ratio. I tried setting up the geometry on my 283 with the stock stamped rockers and I could not get them to leave a mark so I could not tell if they are centered on the valve. When I put them on the 350 it was clear where the rocker was riding on the valve. I know roller fulcrum rockers would have been better but I am on a budget and still wanted the geometry to be correct. The balls do have grooves for better oiling and less surface area so there is some reduced friction.

helrazr3 01-24-2013 10:14 PM

Quote:

Originally Posted by Richiehd (Post 1638219)
Just so you know, roller cam is different than roller rockers.

yes i do but i figured it all goes hand in hand if im going with a roller cam and lifters you would just do the rockers to.

MouseFink 01-25-2013 07:00 AM

Aftermarket performance flat tappet and roller camshafts usually have higher valve lift and require a higher than stock spring rate in order to control valve action. Stock rocker arms with ball fulcrums are not designed to be used with more than 300 lb. valve spring pressure. Grooved rocker balls will give you an additional 30 lb. open load but open valve spring pressure more than 330 lb. should always be used with full roller rocker arms. When using high lift camshafts, full roller rocker arms will reduce oil temperature, diminish side load on the valve stems which reduces wear on the valve guides. Tight valve guide clearances and the use of self lubricating phosphor-bronze valve guide liners will allow more accurate valve seating.

This is why full roller rocker arms should be used with high performance flat tappet or roller camshafts. GM came to the same conclusion in 2000 when they introduced pedestal mounted, roller fulcrum rocker arms and the factory ball fulcrum rocker arms went the way of the Do-Do bird.

Richiehd 01-25-2013 04:00 PM

Mousefink, I agree 100%

Mertz, I dont think you can do a proper geometry check with the stock rockers, besides their ratio is all over the chart. Check those rocker for blueing from heat. I had very low hours on these rockers. Watch here:


helrazr3 01-25-2013 05:59 PM

ok so do i need to change the valve springs too? its not a big race engine with crazy stuff i started this idea because i know roller is an upgrade from stock and i can eliminate the stock rocker arm adjustment from the equation

oldbogie 01-25-2013 07:09 PM

Quote:

Originally Posted by helrazr3 (Post 1638758)
ok so do i need to change the valve springs too? its not a big race engine with crazy stuff i started this idea because i know roller is an upgrade from stock and i can eliminate the stock rocker arm adjustment from the equation

Actually no you can't eliminate the rocker arm adjustment from the equation, rollers are adjusted just like the sliding shoe by using the rocker nut to set the lash of a solid or travel of a hydraulic. The one thing that tends to be easier is seeing where the contact point is between the rocker's roller and the stem as knowing this is essential to picking the best length push rod.

Push rod length and its effect on where the roller (or sliding shoe for that matter) establishes two things:

- The off center forces introduced into the valve stem that cause it want to bind in the guide, this is a wear issue for guide and stem and an oil seal issue for the stem seal. You see the result of this in the guide wear being an egged shape in the direction of the rocker rather than uniform wear around the guide bore.

- The other is dynamic rocker ratio; the stated rocker ratio is a static dimension from the center of rotation to the push rod cup on one side and the tip contact point on the other. Production parts tend to be a bit sloppy here. However, in addition to that problem is the fact that the push rod end and the valve stem end actually make different motions of rotation so the dynamic ratio of the rocker is always changing a little from the static dimension calculation. So using a push rod length that keeps the movement of the tip across the stem to a minimum, also keeps the ratio more constant to the advertised. God, I'm beginning to sound like Jim Miller!

Bogie


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