Worn rocker shaft replacement

[2robert4]

Hi All

Have any of you guys removed the rocker shaft assy without removing the Cylinder Head?  The Workshop manual suggest draining down the coolant and loosening off all of the cylinder head retaining bolts to negate distortion. I can understand the need to drain the coolant just in case but disturbing all the head nuts could be a recipe for disaster as the head gasket could loose its seal. I have always been used to removing the rocker shaft assy when removing the cylinder head obviously but surely removing only the nuts securing the shaft assy is enough. Your comments please gentlemen. 

Regards
NP

[anglia67]

Hi
I'm sure if you drain some coolant,maybe take plugs out in case you've some compression left as not to disturb head gasket when you remove all nuts.ive never had any problems using this method
Allan

[noddy]

Hi NP,

I changed the rocker shaft on my engine in November. 

The advice given in the manual is good practice and is the safest way of doing it.  However it should be posible to do it without loosening all the the nuts - and not have any problems afterwards. 

In the end I actually removed the head - so that I could lap in the valves and replace the valve stem seals.

Roger

[2robert4]

Thanks for your replies.

My take on the job is to remove the plugs partially drain the coolant remove the minimum of retaining nuts remove the shaft and rebuild with a nitrided shaft and replacement rockers rebuild re torque all head fasteners crank over the engine with the plugs out to observe any liquid out of the plug holes if all ok fit plugs and start up reset tappets when warm. Otherwise I may as well just remove the head if I have to untorque all the head retaining nuts which seems a waste as the compression is even and good at 175 psi all round. What does the team think?
NP

[canuck]

The advice on caring for the cylinder head stud/nuts is varied.  The workshop manual is erring on the side of caution. Depending on the type of head gasket you have may not be necessary to completely 'undo' all the head nuts.

I have removed many rocker shaft assemblies without removing the cylinder head and with mixed success. 

So what would I do?

Drain the coolant is for sure. I would remove the sparking plugs. I would back off all the valve adjusters completely.  I would sequentially loosen all the cylinder head nuts.  I would loosen them at 10 lb/ft increments in correct sequence and stop at maybe 5-10 lb/ft, or until they are loose due to the cylinder head stuck by the gasket, or studs etc. This is quite loose, the cylinder head and gasket should not distort too much and this will still allow the smaller rocker shaft fasteners to be removed easily. 

Do the R&R on the rocker assembly and re install.

Note:

While there I would pay attention to the tops of the rocker pedestals at the head stud nuts location. If the OE alloy pedestals these tend to compress around these head nuts, (particularly if the thick hardened washer is not used), and the bearing surface is no longer flat.  Sh*t can happen.

Re surfacing these pedestal surface to flat and using the thick hardened washers will fix this however the ultimate would be to swap these alloy pedestals for cast iron ones, (think Marinas, MGB etc.). Let us know how you make out.

Bruce

picture courtesy of the WWW

[johnmann]

This was one of the first jobs I did as a young lad on my first one-point-five back in 1982. I'm pretty sure I followed the Haynes manual procedure and had no problem with the head. The shaft however was VERY worn, with great gouges in it. I recall the biggest problem was getting the new rocker arms onto the new rocker shaft.
John.

[canuck]

Mar 13, 2017 18:42:33 GMT johnmann said:

This was one of the first jobs I did as a young lad on my first one-point-five back in 1982.  The shaft however was VERY worn, with great gouges in it. I recall the biggest problem was getting the new rocker arms onto the new rocker shaft.
John.

John

You are right, it is incredible what happens to these rocker shafts over time. 

Below is my 'collection' of worn shafts.

 

 I have renewed many a rocker assembly and have become quite good at it. I machined up some bushing replacement tools, have a suitable reamer & hone tool.  I picked up some cast iron pedestals as spares from an auto jumble, just in case!

Bruce

[casper171072]

Interesting thread, I have just bought a 1.5 which is a bit tappety compared to my Wolseley 1500 it replaced.  I am about to get round to adjusting up the tappets but after reading this maybe its the rocker shaft, I didn't realise they wore like that.

[2robert4]

Further to the previous posts I did indeed drain the coolant remove the spark plugs and replace the Rocker shaft and pedestals with out much difficulty and retorqued the head and reset the tappets when hot. However now that I have covered some 600 miles and have had to set two errant tappets on more than one occasion I am of the opinion that not only were the rocker shaft and arms badly worn but it would appear the camshaft and followers in two positions could well be worn as well. What does the team think?

[noddy]

Which tappets are you having to reset? - if they are exhaust ones the it could indicate a bit of valve recession (exhaust valve on cylinder 3 is especially prone to this).
I would doubt that the camshaft or followers are at fault - unless they have been damaged somehow or starved of oil.
It might be worth re-torqueing the head and pedastals - just incase anything has moved in the 600 miles of running so far.
Hope this helps,
Roger

[canuck]

Nov 3, 2017 20:52:17 GMT 2robert4 said:

 now that I have covered some 600 miles and have had to set two errant tappets on more than one occasion I am of the opinion that not only were the rocker shaft and arms badly worn but it would appear the camshaft and followers in two positions could well be worn as well. What does the team think?

The followers (if original) could be worn but wouldn't show as quickly/dramatically as you mention, that being over the short number miles you write.  If you have changed your oil regularly, that contains or you do add some ZDDP then you can rule this out.

I should think that the adjuster, (physical and personal ) may be at play here?  These adjusters are crude, and difficult to get precision with, particularly if the slot in the screw is worn.  I do set my valve adjusters at 0.015" cold and forget about them.  I do not mind a bit of 'sewing machine' music under the bonnet. To me this says, healthy engine!

FWIW the 600 miles you write is about a month of driving for me during the summer here so if I was having to adjust them this often,  well ............... 

Roger does bring up an interesting point however, if your cylinder head is 'old' and original then this valve seat recession could be a case to investigate.

Back to you

B

[2robert4]

The head gasket was replaced and the valves lapped in a couple of years ago but the rocker arms were not replaced at that point. I have rechecked the head bolts and the pedestal bolts but all is well there I will have to keep using the vehicle and see what happens next and report back?

[anglia67]

Hi my thoughts for what there worth.are the tap pets getting noisier? Could be lack of lubricant to these tappets,ie blocked oil gallery to these tappets .way way back in1970 my father bought a Triumph 2.5 injection which had a lack of oil ways in the rocker area which would mean tappets would get very noisy quickly,but a really nice car otherwise.
if tappets are getting less gap then it's a good chance that they are recessing.good luck