An engine built from bits

This thread is for discussing technical topics.

Moderators: Ian Grace, Will Grace

Post Reply
Alice
Posts: 25
Joined: Mon Jan 08, 2007 4:04 am
Location: Brisbane, Australia

An engine built from bits

Post by Alice »

I have never had a complete OHC engine, only piles of parts gathered from various sources (see "Minnie's Story" in mag M140). Recently I decided to do some sorting of same, with the aim of determining what was there and what was missing. Where possible I have been restoring and loosely assembling as I go along. This basically is not a case of picking the best bits, rather the "least worst". There are multiples of some parts, although some of these are of scrapmetal value at most, and I am routinely discovering little differences between seemingly the same component. There are two blocks, both 1930 and made to take the DDS generator (dynamo to UK members), and three front gearcases the best one of which I had painstakingly restored before realising it was for the earlier small generator!
There are two heads, and it seems they are not necessarily both related to the two blocks. One had a fairly rough finish to the casting outer surfaces, and the other was much smoother. The first has a brass bushing to take the camshaft vertical drive pinion. The other had a steel sleeve and two roller bearings instead of the bush. I take it that the latter is a later version. Question: Is the brass bush one piece, or two flanged items end to end. And can the whole shebang be pressed out of the head, or alternatively just the bush?
Question: I have found a steel plate, just under 0.1 inch thick, that is obviously part of the "flexible" coupling between generator and cam drive pinion. Surely there must be something more substantial to the coupling, or is that it?
I'll leave this here for now, but be warned that more questions are likely to follow in this thread.
Ian Grace
Site Admin
Posts: 5035
Joined: Sun Nov 19, 2006 12:55 am
Location: USA

Re: An engine built from bits

Post by Ian Grace »

Hi Barry,

Sounds like an interesting project with lots of teaching points along the way!

The head with the vertical drive bush. The bush was never a Morris part, but many of the original roller bearings/sleeves were replaced/repaired by machining up a simple bush. Easier and cheaper than sourcing the original bearings/sleeve when they became worn or broke up. I had one of these 'home-made' bushes in my Semi-sports and it worked fine. But you just need to remember to add an oil groove on the inside to make sure it doesn't run dry.

As for the flexible coupling, the originals were made of two thin rings of spring steel held together by four pressed bushes which took the four special attachments bolts for the two forks. These special bolts have round heads, but with a flats on them which engage with the flats on the forks, so they cannot turn when you do the nuts up. I suggest if you don't have original parts in this department that you order the correct new items because this coupling takes an enormous load because of the resistance of the cam to turn with all of the rocker fingers pressing hard on it (try to turn the coupling by hand when it is connected to the cam and you will see what I mean!). It really is a weak part of the engine and needs setting up perfectly if it is not going to give you grief down the road. In particular, you need to make absolutely sure, when everything is assembled, that the vertical drive runs exactly true with the dynamo. If not, the coupling will tear itself apart very quickly. You also need to make sure that, when the coupling is in place, it is not distorted vertically. In other words, both forks need to be positioned vertically with respect to each other so that the coupling runs perfectly flat. This is achieved by shimming under the dynamo.
Alice
Posts: 25
Joined: Mon Jan 08, 2007 4:04 am
Location: Brisbane, Australia

Re: An engine built from bits

Post by Alice »

Hi Ian,
That's interesting about the bushing for the drive pinion. I will be aiming for rollers, but will keep the alternative in mind.
Re the flexible coupling, your info reinforces my memory of ones seen on other people's cars.
Many of the parts I acquired came from a car which had been given to a couple of young lads. They obviously thrashed it to death and beyond, as witnessed by a camshaft with lobes worn down to little more than round, one conrod bereft of whitemetal and the matching crank journal badly bruised, and various other signs of a very low and sludge-filled oil level. BUT here's the "believe or not" one: The drive yoke on top of the generator had the splintered remains of a "coupling" obviously made from a circle of 3-ply plywood! Can anyone top that?
Ian Grace
Site Admin
Posts: 5035
Joined: Sun Nov 19, 2006 12:55 am
Location: USA

Re: An engine built from bits

Post by Ian Grace »

I might be able to top that!

When I was on Ascension Island during the Falklands War, I came across two Austin Sevens that had been on the island for decades. Of course, the nearest Austin parts supplier was probably over three thousand miles distant to the north. One of the cars had a distributor cap made of a large round chunk of cork, roughly hollowed out with a knife, and with the five wires stuffed through it!
ian judd
Posts: 176
Joined: Tue Jan 08, 2008 6:01 pm

Re: An engine built from bits

Post by ian judd »

Barry,
The rollers can be replaced by sealed ball races with a spacer between them. Inexpensive and effective. The hole in the head needs to be honed out a thou or two as standard races are exactly the same size as the hole so won't quite fit in. The later camshaft as fitted to M Types is available, but old cams can be successfully rebuilt.
Post Reply