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Free Rocker Shaft Fix (new version)

Posted: Thu Apr 07, 2011 8:02 pm
by Old Fogey
The post currently in Shop Talk that I did on the rocker shaft change-over was a bit, well, not so much misleading as inadequate. It caused a lot of head scratching, but in my defence I was a bit new to posting technical stuff and it's very easy to miss out important things when YOU know how but are not used to showing others.

So here's a new version. This time hopefully I'll get it a bit more understandable. Admin, feel free to change the old one in Shop Talk for this if you think it's better.

First off, let's understand why we are doing this.

Here is a pic of a very worn shaft:

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Due to the pressure from the valve springs and the cam, the rockers wear each of the shafts on the under side. Now, normally when a part is worn like this, the only recourse is to replace it. But here we are lucky. Because both the shafts are identical and because of the way the rockers are arranged, the shafts can be swopped one for the other so that the rockers will ride on fresh metal. You can see the arrangement here:

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I had a bit of a surprise with the head I was doing this on. One of a pair that came in a job lot of parts, in a disgusting mess.

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when I cleaned it down for the photos I found that someone had already done this modification! But done it wrong!

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Check out the oil holes in the shaft. These are supposed to point down to spray the camshaft lobes.

(I changed them round and removed the cam carrier for this pic so that you can see where they are supposed to be)

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OK, back to where we were.

Hopefully, if you have the heads off you removed them with the cam in such a position that the rockers were all nearly free ie. with all the cam lobes pointing in towards the head.
Back off the tappet adjusters until there is no spring pressure on any of the rockers.

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I like to disturb things as little as possible (although these heads will be getting totally stripped eventually due to their condition) but if you leave the cam carrier on the head after removing the six 12mm bolts, the shafts will only come out of the carrier towards the rear of the head. As these heads were already off I took off the pulley and rear timing case cover for the next step.
Further on I will show you how to do the next step on a head that is on a running engine, without taking anything else such as pulleys, covers, timing belts etc off.

Gently tap the shafts out of the cam carrier using a drift. They are not normally a tight fit so once you have them started you can usually pull them out the rest of the way by hand.

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Rockers and their springs will stay in place while you swap over the shafts

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Now you can see from this that simply moving the inlet shaft down to replace the exhaust shaft and vice versa will result in the oil holes pointing up as in the previous picture.

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So the shafts have to be turned end over end to rectify this.

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Lube up the shafts and slide each one back into place, replace the six bolts and torque them down evenly. I don't have torque figures for these bolts but about 12 ft/lbs should be enough

If you have done the job right it should look like this:

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All that remains now is to reset the tappets and fit the rocker cover back on.

To do this on a head that is still on the engine.

Follow the procedure as above but don't go removing cam belt, pulleys, covers, tack drive bolts or anything else.
Since there is nothing to get a hold on to pull the shafts out and you can't get to punch them from the front you need to use something with a right angle on it to get the shaft started. I simply used a pair of circlip pliers to give the shafts the initial push. Once they have moved out the back somewhat, you can get hold of them and pull them the rest of the way.

I mocked up the head as if it were still on an engine:

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Use your right angle implement (whatever) to get the shafts started:

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No problem with getting them past the fuel pump/tach drive:

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So now proceed as above. You should be able to do each side from start to finish in 15 minutes unless you hit something unforseen.

Re: Free Rocker Shaft Fix (new version)

Posted: Thu Apr 07, 2011 8:59 pm
by ericheath
Nice work again. We sure appreciate your input here. Hope to try this later this year.

Re: Free Rocker Shaft Fix (new version)

Posted: Thu Apr 07, 2011 9:05 pm
by robin1731
That shows it exactly. Now the guy that was all screwed up on the other thread knows more too. ;)

(that guy would be me) :roll:

Re: Free Rocker Shaft Fix (new version)

Posted: Thu Apr 07, 2011 10:21 pm
by Whiskerfish
Very good action1 action1 action1

Like to give this a day or two here and then move it. John if I forget give me a nudge in a couple days please.

Re: Free Rocker Shaft Fix (new version)

Posted: Fri Apr 08, 2011 8:22 am
by lcallison
Thank you for the excellent article. I'll be doing this on my 76 shortly. Maybe it'll be the fix for that noisy beast.

Re: Free Rocker Shaft Fix (new version)

Posted: Fri Apr 08, 2011 9:07 am
by Sagebrush
Good job John, even I can understand it action1

Re: Free Rocker Shaft Fix (new version)

Posted: Fri Apr 08, 2011 11:32 am
by rcmatt007
excellent how to! Good work

Re: Free Rocker Shaft Fix (new version)

Posted: Fri Apr 08, 2011 11:42 am
by rogue1000
Excellent how to, John, thanks...The symtoms that would lead one to suspect he needed to do this fix would be excessive noise? Maybe coupled with high milage?

Re: Free Rocker Shaft Fix (new version)

Posted: Fri Apr 08, 2011 4:21 pm
by Old Fogey
Just noise really Brian. The worse the wear the lower the oil pressure under the rockers as it can bleed out too fast, causing more wear. I guess in extreme cases the pressure throughout the engine would drop because of it since the oil will take the path of least resistance.

The the top end will get over oiled, the crank bearings will be starved......

The extra oil will carry the bits of metal worn off the shafts and the rockers down to jam the oil pump....

The shafts will break in two and the rockers will punch holes in the covers and in your legs.........aaaaaaaaaahhhhhhhhhhhhh!!!!!!!!!!!!!!!

Paranoid? Moi?

Re: Free Rocker Shaft Fix (new version)

Posted: Fri Apr 08, 2011 8:36 pm
by 05c50
Very nice "how to", John. The pictures are excellent, and even with your accent, I could understand everthing you said. :lol: :lol: I was just wondering about the wear on the inside of the rockers. Have you ever seen rockers worn to point that they were unusable?

............Paul

Re: Free Rocker Shaft Fix (new version)

Posted: Sat Apr 09, 2011 8:20 am
by Old Fogey
The simple answer to that is the only ones I've had that would not be used again are the ones in the article! Reason; they had already been turned and then used in an engine with severe oiling problems (the crank shells were worn though to the copper!).

The vast majority of these heads will never have had the shafts removed, so a quick turn around and you would be good to go for another 30 years!

Re: Free Rocker Shaft Fix (new version)

Posted: Wed Apr 13, 2011 6:18 pm
by MSGT-R
Old Fogey wrote:The the top end will get over oiled, the crank bearings will be starved......

The extra oil will carry the bits of metal worn off the shafts and the rockers down to jam the oil pump....

The shafts will break in two and the rockers will punch holes in the covers and in your legs.........aaaaaaaaaahhhhhhhhhhhhh!!!!!!!!!!!!!!!

Paranoid? Moi?
Dude, we really must get you back on your meds! :happy_251:

Re: Free Rocker Shaft Fix (new version)

Posted: Thu Apr 14, 2011 9:40 am
by giant81
MSGT-R wrote:
Old Fogey wrote:The the top end will get over oiled, the crank bearings will be starved......

The extra oil will carry the bits of metal worn off the shafts and the rockers down to jam the oil pump....

The shafts will break in two and the rockers will punch holes in the covers and in your legs.........aaaaaaaaaahhhhhhhhhhhhh!!!!!!!!!!!!!!!

Paranoid? Moi?
Dude, we really must get you back on your meds! :happy_251:

How do we know this isn't him on his meds? I wonder what he'd be like off of them.

Could this be something I might want to look at doing on my 81? I think the odo says about 65,000 miles on it and I'd suspect this hasn't been done. I've got time before my parts arrive. I suspect it wouldn't hurt to switch these around.

Re: Free Rocker Shaft Fix (new version)

Posted: Sat Apr 16, 2011 11:00 am
by Anim8or Earl
Thanks Old Fogey, that was very easy to follow.

Re: Free Rocker Shaft Fix (new version)

Posted: Mon Dec 12, 2011 6:52 pm
by jameswells
Hi John

Would this be a good thing to do on any GL that's done 50,000 miles? Or only if it looks necessary after examining the parts? Is wear usually visible?