My 4G Restoration Blog

[paul.wirdnam]

As I'm waiting for the crank grinders to open in the new year, thought I'd make a start on the head and rocker box. Couple of question please:

How do you adjust the end float of the rocker spindles in the rocker box? In the photo below, the new stainless nuts are fully screwed in with a single fibre washer and the rods can move sideways at least 3/16". Obviously, if the rockers, valves and springs were fitted, the spindles would be much less likely to move but am I missing something?



The four rocker box head bolts (below) have a single flat on their shoulder. What's the purpose of this single flat?



Thanks for any help you can give.

[paul.wirdnam]

I think I have the answer to the rocker box head bolts....the flat is there so you can remove these head bolts without dis-assembling the rocker box.

But still hoping someone can shed light on my rocker spindles end float....

[paul.jameson]

I suspect that the end float of the rocker spindles might be a rocker box preservation initiative by Ariel Motors. If you are daft enough to refit the rocker spindles without checking whether the valves are open at the drive side (as opposed to timing side) of the rocker box you can push the spindle in then tighten it with the nuts at the timing side and the rocker spindle will bend just enough to break the rocker box on the drive side. The previous owner on my 1948 4G had managed to do this. Rocker boxes broken in this way seem common on the 4G models.

Provided that you have support at each end of the spindle I doubt there will be a problem.

[nevhunter]

Won't the end float/positioning of the rockers, (The only thing that matters) be controlled by springs or spacers, like all other Ariels?. The shafts moving a bit doesn't matter much as they have no shoulders. Where does the oil feed come from.? A hollow brass spacer of the right thickness will correct the shafts end movement. Nev

[paul.jameson]

The end float and positioning of the rockers is controlled in the normal Ariel manner, as Nev says. The oil feed comes from the end with the nice new nuts. These nice new nuts go over the end of the spindle and so form its support on the timing side. The nuts are drilled so that the oil goes into them from the outside, then goes down the centre and into the centre of the spindle. So the oil pressure will in time push the end of the spindle towards the drive side of the engine. Thus there is no need for spacers for the spindles as their location is determined automatically.

[david.anderson]

Paul
It is worth considering upgrading the original rocker box. As the original rocker box was flawed in design and resulted in oil leaks, the South Australian Police Force mechanics designed a leak free rocker box which was then used on all police bikes. The Australian Ariel Register commissioned a pattern to produce the police force upgrade and has produced a couple of batches of the rocker boxes. Unmachined boxes are available at $225au. (about half that in GB pounds) http://www.australian-ariel-register.com/default.html
David

[paul.wirdnam]

Paul
It is worth considering upgrading the original rocker box. As the original rocker box was flawed in design and resulted in oil leaks, the South Australian Police Force mechanics designed a leak free rocker box which was then used on all police bikes. The Australian Ariel Register commissioned a pattern to produce the police force upgrade and has produced a couple of batches of the rocker boxes. Unmachined boxes are available at $225au. (about half that in GB pounds) http://www.australian-ariel-register.com/default.html
David

Thank you David...and a couple of us have been in touch with Greg and Col Hill and our boxes are being cast, machined and zinc plated as I type. Very impressed with the photos and, even more so, by the very reasonable cost.

More progress on the rest of the engine as I got my cranks back from the grinders yesterday. Crank pins ground to -10 thou and the main journals made circular (1.234"); shells ordered from Bruce.



With cranks back, I can start making the timing side bushes from leaded bronze (SAE660). Quite a lot of discussion on the FB Ariel Group about the pros and cons of leaded bronze versus white metalled bushes, but the consensus seems to be that modern oils + cartridge oil filter means leaded bronze is better. Bennett Longman (Bruce's son) posted some rather nasty photos of failed white metal bushes after 25,000 miles from his SQ4, and if Bruce/Bennett are using leaded bronze, who am I to argue.

I'll be reaming my new bushes in-situ so have made the following to support the end of the HSS adjustable reamer by indexing it with the outer race of the new roller bearing in the far side. Ali block in far shell held in with a light interference fit and the brass bar is a sliding fit through it. The brass bar supports the end of the reamer. This is the plan anyway....hope it works.

[chris.shearwood]

Hello Paul,
I like your idea of a line reamer tool. What clearance do you intend to use between your timing side bushes of leaded bronze and the crankshafts' journals? And how would you measure it? Bore gauge? Internal micrometer? I understand that the 1.5 thou used with Babbitt material may not be sufficient with the lead bronze. I suppose the use of a Morgo pump may make the tightness of this dimension less critical?
Regards, Chris

[paul.wirdnam]

Hello Paul,
I like your idea of a line reamer tool. What clearance do you intend to use between your timing side bushes of leaded bronze and the crankshafts' journals? And how would you measure it? Bore gauge? Internal micrometer? I understand that the 1.5 thou used with Babbitt material may not be sufficient with the lead bronze. I suppose the use of a Morgo pump may make the tightness of this dimension less critical?
Regards, Chris

Hi Chris, yes, I used telescopic bore gauges and I've set the clearance to between 1.5 and 2 thou. Bushes now made, installed in the crankcases and reamed to that clearance.







Would appreciate comments on my timing chain tensioner....this is how it came. I have several sets of 4G cases and all of them have broken mounting points for the original spring steel strip. Someone has made this steel slipper; you adjust the chain tension by adding washers between it and the casting it is bolted to. It is well made and I plan to leave this arrangement (plus locking tab washer) unless someone advises me otherwise. I should add that a similar mod has been done to my '48 KG...not by me I might add...and it seems to do the job fine:

[roger.fellows]

That's quite similar to the later Mk11 with duplex chain. Looks fine. The later is longer. Have you checked that the chain has a 'ramp' introduction to the tensioner rather than a step? Certainly looks as though it has.