Rocker shaft B18A
 

Have dismantled and cleaned up the rocker shaft assembly on my B18A.

The tappet adjusting ball studs look ok. I can buy a single new one to compare to be sure.

I'm less certain on the other side of the rocker arm, which operates the valves. Wear here looks evident, but uneven and not the same across the eight arms. Very grateful for any wise words here.

The shaft, cleaned up shows significant scoring where the locating springs fit. The whole assembly was in a real sticky mess, so am planning on reassembling to check whether new rocker arm bearings are required. Again, any wisdom much appreciated.

The face of the rocker can be reprofiled. Look for a machinist who has experience working on vintage Triumphs, MGs, Austin Healeys .... They will know what needs to be done.

New rocker shafts are available for a reasonable price.

http://212.247.61.152/us/main.aspx?p...e&artno=418305

If the existing shaft looks dodgy, use a new one to assess whether the rocker arms need to be rebushed.

Many thanks, 142. Shaft surprisingly reasonably priced. Am sure Brookhouse will be able to help of I need one. Machine shop is very good on old stuff. I was thinking I might have needed a good arm for him to copy, but will take them to him and see what he says.

Sleek lemur one on Ebay for B18 Birmingham ! :-)

I think you also need to consider whether the rocker arm bushings need to be replaced.

First off, I would consider the wear on the shaft underneath where the rockers run, not so much under the springs. If this area is scored and worn, for sure get a new shaft.

Then I would try to assess the rocker arm bushings. For the home gamer, these are a real pain in the kiester to replace, as the old ones need to be pressed out, new ones pressed in, any oil holes lined up, and then reamed to the correct size.

Unfortunately, I didn't see any specs in my version of the shop manual. But you might be able to look at them and determine if any face metal has worn through. And then you may be left to just deciding if they are too tight or too sloppy on the shaft.

The valve tip wear pads can be reshaped with a gentle hand on the bench grinder. That's the easiest part of the whole affair.

For me, the job for the machine shop would be the bushings, not so much the pads.

Many thanks, BlueOsprey.

I am wondering wether the pads on some of the arms might need building up. Perversely, two of the screw adjusters on the other side were longer than standard and had no ball pein shape to the actuating tip. An yes, when I took a look at the bearings my heart sank. Similar to small end bearings. Am taking the lot over to the machine shop this afternoon and we can decide what to do.

I have a feeling that I will be visiting eBay- thanks POwen!!

In the 1971 140 service manual, they do provide some guidance on the rocker arm bush wear (should apply to the B18 since the shaft is the same). The SM 'sez' "If wear amounts to 0.01mm (0.0004"), replace the rocker arm bush". The term wear is unfortunate because it implies the change in clearance. I expect that what they really mean is when the clearance exceeds 0.01mm replace the bushings.

The rocker contact pads can theoretically be done on a bench grinder at home (with unworn grinding wheels suitable for the correct surface finish). However, that said I wouldn't. This is a case where prior experience and touch is useful so you don't have an 'oops' with the first rocker that you try. The machinist that I used had a large diameter wheel and a fixture that he had fabricated to keep the rockers square during the resurface process. The cost to resurface all the rockers was low ($40 Cdn) so I was happy to outsource it.

If the contact area on the rocker shoe has a groove worn in it to the point that it requires filling with weld and then resurfacing, that is a significant undertaking to do correctly. I would have that discussion with your machinist to confirm that the rockers are beyond simple reprofiling with a grinder. I would start looking for some rockers from a salvage engine that might be fixed with regrinding before I would consider filling old rockers with weld in the wear area.

There are vendors that sell refurbished rockers (about 100 Euro each). Hiperformance auto in the US will rebush, reprofile and hard chrome your old shaft for $200. That is a very good price so I would email them to make sure that they still offer that service.

http://hiperformanceautoservice.com/...li2o5mb50dsrf1

Thanks 142, as always. I took my rocker shaft and arms to the machine shop this PM. He was very happy with the pads and will give them a very light going-over. He was also happy with the shaft and said the play in the arms wasn't too bad, with maybe 20k left in the bushes. In the end we decided on changing the bushes. I want this engine to be as good as possible.

In other news, he was concerned that one of the old small end bearing had slid out from its rod. But was sure there was nothing unfixable.

He's also asked for my cam, so he can check the new bearings he's just put in. I've gone for a K.

The two oil gallery bungs needed drilling out.

Looks like I will be getting it all back soon. All the other bits and pieces are now cleaned (and dried in the oven at low heat!) and boxed up.

I will give the garage a good clean and I'm on the lookout for a new bench, so I can have a clean and a dirty one.

Then when I start to assemble, be prepared for a new avalanche of questions!

Really, thank you all for such great comments thus far.