Wednesday, June 4, 2014

Refitting the cylinder head.

Ok, now that the head gasket is ready, the head gets the last few things done and is then ready to go back on.
The little stack of rocker spindle cover plates and gaskets goes back on:
Word of caution: you should really leave the cover plates at the back (intake) off until you torque down the head, as they can interfere with the socket/wrench when bolting down the head onto the cylinder block, i.e. there ain't a lot of room there.
There were still two studs that needed to go on the cylinder block:
Something else I forgot to mention was that I tightened the four long through-bolts with a torque wrench. On a standard 850 barrel, I think there are washers there, and I had even got some when I ordered the last few things from Andover. However, they didn't fit in the Maney cylinder. Sure enough, they're not needed, as long as some oil is applied under the bolt head and on the threads, which is good practice anyway. It's important to not use too much oil, which especially in a blind hole could end up with nowhere to go and negate the correct tightness, despite an apparently correct torque reading. It's never really straightforward is it?!
and for my next trick, holding all pushrods into the head. You could do this with some rubber bands or zip ties ... or get a mate to help you. I preferred doing this by myself just so I could concentrate and take my time. It really isn't difficult, it just takes a little bit of care and a steady hand.
The maneuver to refit the head will seem counterintuitive, but the way described in the workshop manual is the way to do it. It's the reverse of how you take the head off, so you start with the head tilted at a 90° angle behind the cylinder block, pushrods facing forwards. Then you tilt the head forward until you locate the studs, and the pushrods are close to their tunnels.  There isn't a whole lot of room, and it's very important not to nick or bend the pushrods. Once you've cleared the cylinder block, you can free the pushrods, which should find their place on top of the cam followers, and lower the head. At this point the studs prevent the head from moving around and you can focus on locating the pushrod cups on the rocker ends. Again, this needn't be a fiddly, frustrating, maddening task: use a powerful light to look through each exhaust valve housing and guide the pushrods home with a thin screwdriver: it took me two minutes to do them all. Once you've got them, here's a neat trick to avoid having to start over:

The rubber bands keep the rockers firmly into the pushrods' cups.

Alright! It's starting to look like an engine again...
The more keen-eyed amongst you will have noticed two things: I removed the valve adjusters (although this wasn't strictly necessary to be honest), and I removed the front Isolastic mounting bolt, then "dropped" the engine as far forward as it would go.

This gave me more clearance up at the top to refit the head. Sorry I don't have any photos of the maneuver itself buy I was more concerned with not cocking it up than documenting it. Bottom line, there is absolutely no need and no reason to pull the engine out of the frame (with all the complication and extra time and labour to remove and refit the primary, clutch, etc.) "just" to do a top-end job. All in all, I would rate this an easy-to-medium difficulty task, and I'm no mechanic.
It's now time to go around the all important tightening sequence.

I decided to go with Champion sparking plugs this time:


Post a Comment