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GM Rocker Arm Material

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Old 12-13-2011, 05:06 PM
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Default GM Rocker Arm Material

I was wondering if anyone knows what material the factory rocker arms are made from. I heard they're an investment casting but I can't seem to find the grade of material.
Old 12-13-2011, 06:39 PM
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you are going to be looking at a high strength low alloy steel most likely one of these alloys: 4140, 4340, 52100, 6150, 8620 and probably heat treated to increase hardness and tensile strength.

If you want to know the actual temper you can do a hardness test and derive the tensile strength to give you a better idea. and if you cant find it on google sent it to a material lab, pay 200 bucks and get a spectum analysis of the rocker make up and they can tell you.
Old 12-13-2011, 07:35 PM
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The OEM rocker arms seem to be pretty strong. I don't recall hearing of any OEM rocker arms failing ... has anyone else seen or heard of them failing? I'm talking about the rocker arm itself, and not the OEM bearings which are known to fail.

OEM rocker arms with the Comp Cams Trunnion/Bearing Upgrade Kit seem to be pretty bullet-proof.
Old 12-13-2011, 07:35 PM
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Powderd Metal.

Tim
Old 12-13-2011, 07:56 PM
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So I would assume forged powdered metal similar to the connecting rods ?
Old 12-13-2011, 09:19 PM
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The book How to build High-Performance Chevy LS1/LS6 V-8s states that they are investment cast.
Old 12-14-2011, 04:50 AM
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There is a member on CF that goes by the name "Eric D" who works for GM. If you need the specifics, maybe he can get them for you.
Old 12-14-2011, 05:21 AM
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I'm looking for the actual grade of material. I know I can send it off to be analyzed but I'm looking for a more affordable option. I did read somewhere that they're investment cast but that just explains how they're made. I hope someone has some info because I could not find it.
Old 12-14-2011, 07:01 AM
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Originally Posted by v8pwr
I'm looking for the actual grade of material. I know I can send it off to be analyzed but I'm looking for a more affordable option. I did read somewhere that they're investment cast but that just explains how they're made. I hope someone has some info because I could not find it.
Looking to make some rocker arms?

Last edited by SweetS10V8; 12-14-2011 at 08:57 AM.
Old 12-14-2011, 11:41 AM
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Yes I am. I have some ideas in mind and I'd also like to evaluate the factory setup. I have some great resources @ my disposal so I'd like to put them to good use. Maybe other could benefit from this as well.
Old 12-14-2011, 12:02 PM
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Originally Posted by v8pwr
Yes I am. I have some ideas in mind and I'd also like to evaluate the factory setup. I have some great resources @ my disposal so I'd like to put them to good use. Maybe other could benefit from this as well.
Thats the reason your propably going to have to pay to find out exactly what the material is...THe people who have already paid to figure it out wont give it up, but who knows. Maybe someone on the forum would be willing to let the information out???

Florida.......Scorpion/Crane????

You cant beat a set of stock rockers with a trunion upgrade in most cases! As we all know the stockers are a fairly good design.
Old 12-14-2011, 12:09 PM
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Someone has allready fixed the issues with the stockers. Changed the material and bearing design.

They didn't get rich off of it. GM's gov bail out cost them money.

Tim
Old 12-14-2011, 06:28 PM
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Are you going to machine these or are you going to cast them? If you are going to machine them go with bar stock high strength low alloy carbon steel. Heat treat it to 180ksi-190ksi and you are good to go. If you are going to make 1-5 sets it will be way cheaper just to machine it. There is still a couble $k in NRE for a casting shop just to set up a mold. Sometimes if you have access to a good 3d printer you may be able to get some of the cost out of it depending on the material you use.

and check this out for a start on an FEA. www.rpi.edu/~des/Rocker_Report.pdf

PS
I can help you design these if you are looking to really make a set...i to have resources. Engineering, CAD/CAM, machining, and lots of fab vendors on a speed dial.
Old 12-14-2011, 07:01 PM
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Thanks for the offer GNIUS but that's what I do for a living. I had hoped for some info but I can get it from the parts themselves. I'm not trying to make a career out of I just see a shortcoming. The biggest hurdle for me is time to do it. I would machine them as the tooling investment is too large for me.
Old 12-14-2011, 08:50 PM
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dont know how thew **** i did this x(

happened to about 4 rockers..and yes they were torqued
Old 12-15-2011, 04:04 AM
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Originally Posted by JaYZeig


dont know how thew **** i did this x(

happened to about 4 rockers..and yes they were torqued
How close are you to coil bind?
Old 12-15-2011, 06:05 PM
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Thanks for stepping up to help me GNIUS, I really appreciate it. I'm not trying to build a valvetrain manufacturing company but I would prefer to utilize my time more constructively to possibly benefit this expensive hobby I have.
Old 12-15-2011, 07:17 PM
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Originally Posted by vettenuts
How close are you to coil bind?
And to add ... were the pushrods on those rocker arms bent at all?
Old 12-15-2011, 09:43 PM
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well, the springs were specifically built for the "ls" engine, so i figured there would be no problem, my cam is specd at .600 at the valve, and the pushrods are specd to the cam.

no pushrods were bent, but when the rockers broke, they were pushing down on the retainer part of the valvespring hardware, this may have save the pushrods from bending.

the springs i WAS using were rated at 505lbs springs pressure...ive since then downgraded to some pac-1518 springs and havent had a problem in just over 100 miles since the install.
Old 12-16-2011, 05:00 PM
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Originally Posted by JaYZeig
the springs i WAS using were rated at 505lbs springs pressure...ive since then downgraded to some pac-1518 springs and havent had a problem in just over 100 miles since the install.
You still using OEM rockers (with Comp Cams Kit?) with the PAC-1518 springs? Yeah, 505 lb springs seem pretty stiff.


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