Question about rocker arms and shafts

[arveetek]

Most everyone here on the board claims that the later model stamped rocker arms are better than the older cast style. The claim is that the stamped rockers don't wear as much as the cast. However, I was comparing a set of stock '83 cast rocker arms and shafts to a set of stock '86 stamped rockers, and the stamped rockers were worn down so much, there was probably close to an 1/8" or more gap between the rockers and shafts.

I noticed this because I was thinking of replacing the cast rockers on my '81, due to a bad idle problem. I pulled the '86 stamped rockers out of my parts bin, and even bought some new plastic retainer clips from GM. However, after inspecting the stamped rockers, I noticed they were pretty much junk, and the '83 cast rockers I alos had in a box were in really pretty good shape.

What gives? Are the stamped rockers really any better? It seems to me that the cast rockers with bushings are a better built setup, as long it gets plenty of oil, or is that the problem...insufficient oil? The '83 cast rockers had bushings just like wrist-pin bushings. Seems like a really high-quality setup. The stamped rockers just rub back and forth on a shaft with no type of bushings or bearings. No wonder these rockers were worn out.

Here's a pic comparing the two of them, so you can see them side by side:

http://community.webshots.com/photo/286393940/1311232722029465272YkBVXX

Casey

[john8662]

Casey,

After doing EXTENSIVE research on this I have come to a conclusion.

I was worried about you when you re-used your 82-84 rocker shafts and rockers.

The geometry on the 81-84 rockers is better, but they DO wear substantially. Take apart your shafts and observe the wear on both the shafts and the brass bushing inserted in the rocker itself. The tips of the rockers that contact the valve stems also have more wear than what I'd like to see.

I've talked with The Diesel Depot about this numbers times. I had actually started to build up a set of the 82-84 shafts for my 6.2 build and possibly the 6.5. The stopping point was getting bushings for the rockers themselves (which are NOT available anymore). I had already machine solid rocker shafts (to combat possibly breaking shafts) then hard chrome coated the shafts to combat wear. But I couldn't get my rockers re-bushed, w/o having a batch custom made somewhere. They could still be built, but went another route. Another mystery is I could not find a clearance specification for the rocker bushing to shaft, nada, even in the GM 6.2 Manual.

Numerous sets of the 81-84 rockers were taken apart at TDD to find one set that wasn't worn badly to put on a test engine. TDD sent me a video of the rockers to see why they wear badly. The end result is that they don't oil very well at all. There really isn't that much oil that flows through the pushrods in the end, probably due to the high load on the lifters below because of high spring pressure, etc. Neither sets REALLY oiled great, but the newer style will wear less given the oil that they have, less contact/wear points.

Ok, what did I end up doing?

TDD rigged up a way to measure wear on the 85+ rockers. While these things look sloppy and have slack, they're supposed to. Trouble is getting them even. TDD rigged up a way to measure wear on various places on each rocker, basing wear off a new OEM rocker. TDD found that the rockers vary dramatically, even on one set. So rockers of a certain wear are thrown out, while others are categorized into groups to be setup in a set. The idea in stock OEM is that Hydraulic lifters will be capable of taking up the valve clearance slack, which they can, to a point...

I've got a set of their custom rockers in my '86, came with NEW retainers, the rockers are even, the shafts are polished for better oil flow and to examine wear. Nice, easy, and trouble and hassle free.

http://www.thedieselpageforums.com/photopost/data/503/medium/TDD-balanced_Rockers.jpg

End result, replace them! I wouldn't build another engine on the "assumption" that the rockers didn't have much wear.

Contact TDD and inquire about pricing, etc.

My engine idles pretty darn smooth! Engine is Balanced and has the updated rockers. Installed 6.5TD injectors too (that helped as well, high pop pressure with a 6.2 pump helped stabilize the pop off, it's a theory). But, this 6.2 doesn't idle as well as a DS4 6.5 does, mainly when HOT and worked hard (or hotrodded, haha).

John

[arveetek]

Wow! Thanks John! That's why I love this forum....tons of info.

I keep thinking about my rough idle problem which I've lived with for over a year now. It idles great when cold, and it even idles perfectly smooth like a DS4 6.5L after it's been worked really, really hard.....but only for a few minutes. After it cools back down to normal operating temp, it's back to rough idle.

I can detect a hint of valve train noise, but most of the noise is coming from the gear drive, which I don't think would make any noise if the engine ran smooth..... The DSG instructions clearly state that any problems in the valve train would result in noise from the timing gears.

I was starting to work towards installing the the '86 stamped rockers, but then concluded that they were junk and wouldn't help anything.

There's another company making custom rocker assemblies for the 6.5L as well....in fact, didn't you buy a set? I remember reading about them on the 6.5L forum, but I thought it was from another company, not TDD.

Since I have a brand new engine, "balanced" so to speak, at least using my own measuring devices, w/new injection pump and injectors, there's really not much left to cause a rough idle, although I do wonder about the quality of the rebuilding on my injectors...

Thanks John!

Casey

[john8662]

Yep, I did have the custom rockers from the other outfit in Portland.

I sent them back when I noticed that they resurfaced the tip surface where the stem contacts the pad. No control of how much was taken off, could be a little, or a lot. Besides that they were rock solid..

I'm going to do a "mixbreed" for the 6.5. TDD rockers/shafts and then assembled with the brads that PEB used.

I wouldn't just throw the rockers you have in after learning what I have...

Ditto on the timing gear noise. This new setup is much quieter than the last, but this one makes odd noises at idle, not always even sounding. But... I listen too much to the engine. Got the radio fixed now I can concentrate on some tunes instead.

[grape]

i milled the stock pedastals off the heads and built my own shaft set up with jesel's..........lol.