Hints and Tips - Rocker shaft and head...

From: Don Rowley
Sent: 07 June 2002
To: British-Cars-Pre-war
Subject: And How About An ALVIS Problem For A Change?

I have just tightened the cylinder head down during engine reassembly only to find that rocker arms 4 & 5 are binding, almost solid. The whole rocker assembly is original with some wear, unfortunately a new shaft and rockers are not yet available otherwise I would have replaced the old ones. However, the rocker arms moved freely before tightening down the head.

My assessment is that in tightening the head nuts I have introduced some distortion. The head gasket is a standard Red Triangle copper, asbestos(?),copper sandwich and all head nuts were torqued down in the correct order by the same amount to 38 lbs.ft. as per TVAM.

My thoughts on how to proceed are to try easing back on the head nuts holding down the rocker gear closest to rocker arms 4 & 5. But, if this works are there likely to be unfortunate side effects - warped head, head gasket likely to blow, etc.

Advice on what to do next would really be appreciated.

Very many thanks in advance.

Don Rowley

1927 Alvis SD12/50 Beetleback


From: Stuart
Sent: 11 June 2002
To: Don Rowley
cc: British-Cars-Pre-war
Subject: Re: And How About An ALVIS Problem For A Change?

Don, I hope you will forgive a reply from a non Alvis person. I waited politely first to see if an expert would leap into the breach!

It seems unlikely that you have distorted the head, unless you have made the same mistake as I did recently, namely, put the studs into the block with Loctite, wipe off the excess round the base of the stud but unwittingly leave a transparent fillet about 5mm. wide and 20 thou thick round the base of one stud. Wait for it to harden nicely then put the head on....that distorted the alloy head on my Seven most effectively. Same could apply to a raised fillet of metal round a stud hole, under a rocker pillar, say - no offence intended about your engineering integrity, I hasten to add! I fear the next move may be to release the head studs and remove the rocker gear. I would want to stand the assembly on a face plate, if this is practicable, to see if there were gaps of several thou under any of the pillars. I don't know if it is possible to get a straight edge along the faces of the pillar mounts in the head to see if that's all flat while it is all still bolted down? Can the rocker shaft be rotated in the pillars on assembly or does it all have to line up in the same place it came from originally? You can see what I'm thinking here, no doubt - have accumulated errors combined when reassembled in a different alignment?

If nothing else, perhaps my observations may serve to stimulate suggestions which are more useful than mine. Best of luck!

Regards, Stuart


From: Don Rowley
Sent: 15 June 2002
To: Stuart
cc: British-Cars-Pre-war
Subject: Re: And How About An ALVIS Problem For A Change?

Stuart,

Very many thanks for your suggestions. I am sorry that I have taken so long to respond but I have been without a telephone for a week - it takes that long for BT to get an engineer out! - so no internet connection until now. I will let you know how I get on

Regards

Don


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