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:
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:
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.
when I cleaned it down for the photos I found that someone had already done this modification! But done it wrong!
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)
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.
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.
Rockers and their springs will stay in place while you swap over the shafts
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.
So the shafts have to be turned end over end to rectify this.
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:
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:
Use your right angle implement (whatever) to get the shafts started:
No problem with getting them past the fuel pump/tach drive:
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.
