Rocker Arm question

[Nunyas]

I don't remember reading any information in my manuals regarding rocker arm "slop". Back when I was getting ready to test for emissions I set my valve clearances. While doing so I noticed that the rocker arms seemed to have quite a bit of "wiggle". I mean I could twist it fore and aft, but they did not seem to slide on the shaft. All the cars I've had before my 'B have been over head cam designs. So, I'm not very familiar with what's "normal" for cars with push rods and rocker arms. Is it normal to have the kind of play on the rocker arms that I mentioned?

I want to think it's not normal, because when I look at roller rockers there doesn't appear to be any way for the rocker arm to be able to twist on the shaft if installed correctly. Then again, roller rockers aren't stock. So, I thought I'd ask to be on the safe side....

 

[dklawson]

The rocker gear can handle a fair amount of "slop" up to a point. When new, the clearance between the arm and shaft is probably on the order of 0.001". With wear this obviously opens up. The rocker arms will still operate the valves properly with wear but will introduce noise and experience a loss of oil pressure across the shaft (which is used to distribute oil to the arms). Unfortunately this subsequent drop in oil pressure can exacerbate the wear of the arms. The wear is "normal" as you say but not desirable. I don't know what would be considered an upper limit to what can be tolerated.

 

[DrEntropy]

I've always used the "rule of thumb" that if (requires rocker shaft disassembly) you can visually detect ANY oblong wear in the rocker arm bushings and/or shaft, they should be replaced.

The "real" method involves I.D. and O.D. micrometers, spec sheets and more time, but unless you're just dieing to spend more money and time, the "eyeball mic's" work pretty well /ubbthreads/images/graemlins/wink.gif

Addemdum: Your fingertip can detect differences as small as 0.004", so running your fingertip along the bottom side of the rocker shaft can tell you if it's "worn" to that extend. BTW: Human eyes (well MOST ones, anyway) will see a deviation as fine as 0.002"(!). We're pretty cool animals, huh?

 

[Nunyas]

eh...when I was looking at the rocker arms the "slop" was VERY noticeable. I definitely have a really noisy valve train. This is not the small amount of slop that you guys seem to be describing. I could twist the #3 intake rocker arm fore and aft maybe 0.1 inches. For a better description since I didn't actually measure the movement, I could twist the rocker arm far enough that it only contacted 1/2 of the top of the valve stem. THAT is not good.... right?

The PO claims the head was rebuilt prior to my purchasing the car, but I think they may be confusing a full head rebuild with replacing the head gasket.

 

[John Moore]

You can get the rockers rebushed or get an oversized shaft. When I rebuilt my engine, I ended up buying a rebuilt rocker assembly from Brittek for around $125. That was three years ago, I'm not sure of the price now.

 

[Nunyas]

that doesn't seem like a bad price... I'm half tempted to go for roller rockers when I break down and replace these ones....

 

[DrEntropy]

Are you able to "twist" the rockers that far?!?! They WILL slide side to side on the shaft with little effort (just enough to overcome the locating springs), but if you can turn them at an angle other than 90° to the shaft, they're waaay too worn. Is the shaft getting a good supply of oil? That amount of play will lessen (as stated above) the pressure all along the shaft... I would be inclined to say: Roller rockers are "trick" and all, but a standard set now will definately be adequate for boosting your performance and keeping the top end well lubed, in addition to lessening the impression you've got a Marimba band under-bonnet. The standard rockers are a forged, surface hardned thing of beauty compared to the Triumph stamped sheet, spotwelded things. they will with proper lubrication/maintenance last a long time and take sustained 5K R's PM, no prob. I'd recommend you go with a new stock assembly, soon. -- Just my tuppence worth.

 

[Nunyas]

Well, if I remember correctly, I don't think they're the standard forged rockers either. I could be wrong though, because it has been at least 9 months since the last time I looked under the valve cover. Anyways, yeah, I could definitely twist the rockers that far. I thought it was a bit odd at the time, but I couldn't find anything in my manual that state how much of that kind of play was good or bad. So, I just went with it.

Just out of curiousity, are there any roller lifters made for 18V engines? Also, how's the durability of roller rockers? I'll probably get a "stock" rocker assembly if the price difference is too big, but I'm still curious about the roller parts.

 

[dklawson]

I think what "style" of rocker you have probably depends on what vintage your car is relative to BMC/BL/Rover. The high-performance rockers from BMC were forged. Later under BL sheet metal rockers became the norm. (BTW, You can tack weld the seams on these to make them more bullet proof). Later, some engines started using sintered rocker arms. The earlier two designs are much more desirable.

My Triumph has forged arms, but it was built right about the time BL came into being. The bad thing about Triumph forged arms is that they have no bushing to replace as mentioned above. When they are worn, they're worn out. I wonder if they can be bored out and sleeved though?

 

[DrEntropy]

I never saw a "standard" MGB with aught but forged rocker arms. Of course the roller rockers as 'upgrades' as exception.


[ QUOTE ]
I wonder if they can be bored out and sleeved though?

[/ QUOTE ]

That would be an elegant 'fix' IMHO! but you gotta have a machine shop you can TRUST, IYKWIM.

 

[dklawson]

Yes... or a milling machine in your garage.

I'm still learing abreviations... what's IYKWIM?

 

[Nunyas]

I believe that would be If You Know What I Mean.

 

[DrEntropy]

Prezaktly.

But I'm having a bit of a time figuring out how a milling machine would help ream rocker arm bushes...

 

[Bugeye58]

1. Fixture the arm on the table. 2. Indicate to centerline of bushing. 3. Ream to size. 4. repeat 7 times.
Jeff

 

[DrEntropy]

heheee... Thanks Jeff. That musta been the "Cliff's Notes" version? "Wash, rinse, repeat."... Seven more times.

It's the fixture to hold the rockers confusing me. ~obviously~ I'm no machinist, so how/what to use to securely hold that irregular, funky shape in order to 'thru pass' the ream with accuracy? Some 'soft' jaw facing like aluminum? I have done this job with press, drifts, vice, etc. and reamed 'em by hand... long process; I.D. mic's and lots'a patience.

Would TAIG's "MicroMill" be a worthwhile "home" unit for LBC bits 'n pieces like this? Money IS an object, BTW. "Industrial grade" stuff is outta reach. /ubbthreads/images/graemlins/smile.gif

 

[dklawson]

The Taig, Sherline, and used Unimat lathes are OK for very light work. However, they are more for model makers. Their mills are nothing more than an accessory to their basic lathe designs. I own a Sherline and a Unimat-3 but take most automotive parts to work if they require heavy machining.

There are numerous ways to hold oddly shaped parts like rocker arms. Machining aluminum blocks to serve as holding fixtures is one way. There are also low-temp casting alloys you can use to "pour" around the oddly shaped parts if you don't mind repeating that "seven times".

 

[piman]

Hello all,

I think that it is a bit of a dead end talking about overboring and fitting sleeves. Yes it can be done but what about the rocker tips, if the rocker needs resizing then the tips will also be worn. Machining, locating,buying and fitting sleeves is likely to cost more than replacement rockers in any case. The rocker shaft also will be worn and need replacing.

Alec

 

[DrEntropy]

In the case of the B series, the rockers are bushed originally and replacements are relatively cheap. Shaft replacements as well. If the rocker tips are worn too badly then that would be about the only reason to scrap the rockers.

 

[John Loftus]

Just wanted to jump in and recommend a business .. Rocker Arm Specialists. They do a great job rebuilding Rocker Arm assemblies and do it for a lot less than other vendors (at least the ones that I checked with). I know a lot of people that have used them .. never heard any complaints. The prices have gone up in the last few years but worth checking out.

https://www.rockerarms.com/

Cheers,
John

 

[dklawson]

Thanks for that link. I'll save it for "next time".

As for why bush or re-bush rocker arms... well, back to the TR side of things, the arms on my GT6 cost me $20/each about 10 years ago and there are 12 of them. The shaft did need to be replaced but it was only about $45. In that instance the tips weren't worn but the arms were suffering from TR's common malady of too little oil on the top end. If I'd had a mill back then I would have tried rebushing them myself. Back on the BMC side of things, every A-series set of rockers I've seen has had similar wear to the bushings and shaft long before the tips wore out. I assume the B-series engines wear similarly but I've only worked on one MGB head. Perhaps it would be less trouble and expense to install new components on a B. I bow to those who work on B's more than I.