Tuesday, 22 April 2014

Cylinder Head Assembly

So, I have most of the parts to replace the head, apart from the high temperature sealant recommended by Bruce Longman. Over the past couple of days I have fitted the new head studs:

The thread into the head on later engines is 3/8" BSW, and there is a parallel section on the stud which has to engage with a counterbore in the head. You can see these here:

As the head had been skimmed, much of the counterbore had been machined away. To deal with this, I recut all the head stud threads and remachined the counterbore. Hours later, I have all the head studs in place. After I'd done all this work I ran the 5/16" CEI die down the eight studs in the block, just to make sure there would be no trouble when the head went on.

Next up was the polishing. It's fairly clear from the state of the casting that the fin edges, the 'V' along the top of the exhaust ports, and possibly the sides of the rocker box were polished - maybe also the carburetter flange. Personally I'm not sure that Ariel would have done this, since the rocker box sides would be quite difficult to polish without resorting to small buffs and hand work - there is no access for a polishing wheel, so this would have been time consuming & expensive. I've polished the fins for now; I also like the contrast between the polished rocker covers and the unpolished rocker boxes.

Final thing is the assembly of the rockers themselves. These are all back in, with a couple of replacement shafts (thread damage). One of these went in and out several times - and turned out to be too large on the OD, and with the two grooves for the 'U' washer in the wrong place. The best of the old ones went back in and the replacement will go back to the supplier.

So, now I am waiting for the high temperature sealant and the head can go on!


  1. Is this the "old" head or the "new" head and also did you have the same guy who fixed the broken fin on the cylinder also do the repair job on the broken fin on the head? Also it looks much better now that it is polished.

  2. It's the new head. It's in much better shape than the old one - it's been skimmed and it has new valves, guides and seats.

    I have to admit that I have not repaired that damaged fin - though you obviously haven't spotted it!. The guy that repaired the block is a long way from here, so it is relatively difficult to get it repaired at short notice, and to be honest I am a bit afraid of welding this old material if it is not strictly necessary...

    Thanks for your comments! Keep them coming!

  3. Hi Charlie,
    In my experience it's much easier to place the head on without the rocker-gear in place. it's easier to tork down the head, and you don't have to work against the spring-pressure. After the head is in place, it's straightforward to place the rockers, one by one, with the piston in TDC, no worries at all.....Thanks for your pages, like them heaps :-) Kees Knegt, Netherlands (1953 Mk1 SQ4) https://www.facebook.com/ariel4kees/media_set?set=a.675943799113736.1073741830.100000943656500&type=3
    for some pics :-)

  4. Thanks for the advice Kees. I had a look at your FB page - Ariels and Barney McKenna! Great combination!