The Doc's tranny waggin' Options

[Dr Evil]

I am planing to switch back to the stock rockers. This is too much of a PITA.

[bozo914]

Article in this months Hot Rod details a failure very similar to this. The geometry of the push rod/rocker arm is causing side loading, causing the wear and eventual snapping of the studs. It was blamed on the push rod guide plates being incorrect for the head, having the notch hogged out and inferior (read Chinese) manufactured studs. Don't know if this helps, but it might be good for a couple of clues.

[r3dplanet]

Crap. This is lousy but you might have saved me from making the same purchase. Are these the ones from Corvair Specialties? If so, I wonder if the ones from Clark's would suffer the same problem.

-m.

[Dr Evil]

The brains on the Corvair page feel that CorvairSpecialties parts are cheep Chinese crap. The guy copies designs and has them manufactured in China, with questionable quality - per their opinion.

The more expensive, quality, USA made parts have not seen failures like this.

Bozo - that is interesting. How bad would the geometry have to be off to cause this? I checked and unless my measurements were way off I would be surprised that this would occur. I honestly do not know, though.

[bulitt]

Roller rockers are cool if you are looking to free up several HP or looking to increase the rev limit by reducing valvetrain weight (aluminum) but seems to me for your application the stamped steel OEM's will be more than fine.

[Dr Evil]

I installed them to help with heat, as a precaution. Now that I have driven it, I dont feel I need them, either. I hope I still have the stock gear.....or I will be ordering it.

[MDG]

Hey did you ever finish reupholstering the seats in that zebra fun-fur yet?

I think once you finish that all these other problems will go away.

[VaccaRabite]

Double check your Geo just to be sure, but I agree that stock rockers are a smart idea here.

Zach

[scotty b]

Double check your Geo just to be sure, but I agree that stock rockers are a smart idea here.

Zach

(IMG:style_emoticons/default/WTF.gif) When did he buy a Geo ? Metro or Trakhur ? Or a metro-trakhur (IMG:style_emoticons/default/huh.gif)

[Dr Evil]

How far would the geometry have to be off? I installed these with engine on stand and rotated and checked each rocker for contact and rang of motion. I did check the geometry and the rods were perfect as stock. This was surprising, but I bought the kit to check it and that is what I found.

I am going back to stock, it is just easier.

[wingnut86]

Well,

Again, not a rocket scientist, just one who has fixed their theoretical musings to make them work;-{

I have had to relearn what I knew previously about metallurgy, etc.

Nothing is wrong with Chinese methods, as long as you know that the aluminum they use differs greatly, and all depends on the mix/blend of aluminum oxide (more pure) as well as recycled content when they cast their Chinese boules or cast blanks.

It all looks high grade, only the metallurgist or end user at his wits end knows the truth.

So YES, they may be a perfect geometrical knockoff, and take anodizing perfectly.

Sadly, you get what you pay for or worse. If you take a brand new set of these rockers to a local CNC machinery, request them to make high-end aluminum blanks, maybe add pressed stainless or high grade bronze inserts, you will probably be extremely happy with the result.

And, it will bankrupt your hobby fund for 3 years going forward.

Hope that warms everyone's Xmas Spirits:-)

Dave

[rick 918-S]

I'm not sure I follow you. Based on the type of failure there it doesn't seem to me that it would make a difference what the rockers are made of. It appears they drifted off to one side and started to grind themselves into the stand bolt. US or Chinese the drift would have been the same. Eventually even high end parts would have failed if they were running misaligned. The common failure of a low quality alloy rocker is breakage at the pivot shaft. I think you still have something running out of line.

[rhodyguy]

these are cast aluminum parts?

[bulitt]

I'm not sure I follow you. Based on the type of failure there it doesn't seem to me that it would make a difference what the rockers are made of. It appears they drifted off to one side and started to grind themselves into the stand bolt. US or Chinese the drift would have been the same. Eventually even high end parts would have failed if they were running misaligned. The common failure of a low quality alloy rocker is breakage at the pivot shaft. I think you still have something running out of line.

If the roller assembly in the rocker is loose, or installed in the rocker at an incorrect geometry, or the stud hole is drilled off, it could cause wear.

Look at the picture Mike posted. The stud hole is either offset improperly, drilled at a wrong angle. or the circlips have failed allowing the roller to shift to one side in the rocker.


(IMG:http://www.914world.com/bbs2/uploads/post-1372-1387343329_thumb.jpg)

[scotty b]

...

[tomeric914]

The 140 and 110 have slightly different geometry with respect to the angle that the valves sit in the heads. If you have the wrong rockers OR the manufacturer didn't know the difference, then that could explain why the rockers got side loaded.

[rick 918-S]

The 140 and 110 have slightly different geometry with respect to the angle that the valves sit in the heads. If you have the wrong rockers OR the manufacturer didn't know the difference, then that could explain why the rockers got side loaded.

Or Dr. ordered the wrong stuff. (IMG:style_emoticons/default/happy11.gif)

[Dr Evil]

No, the 110 and 140 use the same roller rockers. If my geometry was off, it was only by a fraction. I would check this, but I have decided to abandon the whole roller rocker thing. The gain just isnt there for me. As for why these all failed and the rocker was shifting on the roller cam, I do not know.

[Dr Evil]

Hmmm, what tomeric said was not false, but what I found on certain sites was misleading. The one that I bought from had one option. American Pi has one options.....Clarks has 2, one for 140 and one for all others. Interesting.
http://www.corvair.com/user-cgi/catalog.cg...mp;page=OTTO-11

[tomeric914]

There's only a couple of degrees difference between the 140 and 110, but at 2000 rpm, the rocker is actuating 1000 times per minute. The rocker gets pulled off center and has nothing but time and cycles to get chipped away at.

The concept of roller rockers is precision and accuracy. That all goes out the window if the engineer who designed them lacks the precise details! The stamped steel rockers allow for lots of play. You're safer with them.