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Spannerman - from CMM May 2014, Issue No. 302

We’ve a saying down at the Chequered Flag that there’s no such thing as a coincidence. Rather, if two things happen at around the same time, then there’s probably a reason for it.

Somebody reminded me of this after they’d read the April piece I wrote, and out of the blue they asked me whether I was going to do a technical article on hydraulic locking.

Now I have to say that it hadn’t come to mind that I should do so, and I was curious as to why they thought that I might be about to pen such a piece. “Well, you mentioned it twice in April, and I thought it might be leading to something.” I had to take a hasty look back to April to try to discover what I’d written, and sure enough I eventually spotted the two references. The first was hidden away in the flood tips from the insurance company when they said “If your engine sucks in water instead of air it could result in serious damage. Don’t even be tempted to turn the key!” and the second was when I was mentioning the dangers of an overfilled sump “..(if) the level of the oil was to reach the bottom of the cylinders. This could effectively prevent the engine even starting, since an attempt to turn over the engine could lead to hydraulic locking.” Now I’m sure many of you know that hydraulic locking is caused by the incompressibility of fluids, but now that the seed has been planted, it might lead on to a further exploration of the topic in coming months.

I must mention my thanks to two contributors to the Classic Motor Monthly Classic Torque Readers Letters’ pages in April. David Mileham sent us a note on the subject of engine lubrication, and Basil Wales wrote on the subject of BMC’s Special Tuning department. Basil was picking up on my comment last month when I wondered exactly when the name of the BMC competition department was called “Special Tuning”. I said that I must dig out some of my old books and look it up. Well there was no need for me find my BMC booklets (and it also helps me avoid having to admit that I seem to have misplaced a box of some of my manuals since I couldn’t actually find my copy of the BMC Competition Preparation handbook) because we’ve certainly found the right man to tell us all about the subject. For those of you that missed the letter, here’s an excerpt from what Basil wrote: “I was the manager of the BMC Special Tuning department for the most successful period of BMC’s competition history and can probably answer most of your questions. The words “Special Tuning” were conceived by Syd Enever, the Chief Engineer of the MG Car Company at Abingdon when he wrote information on how to improve the performance of early MG cars.. ..I still have copies of all these booklets but cannot find any reference to packing the oil pressure relief valve.” I’ve already thanked Basil, and it’s always nice to hear from someone who was right at the heart of things. It was also interesting to hear Basil’s thoughts on the practice of packing the oil pressure relief valve. Here’s what he said: “The practice may well be considered as a way to compensate for worn bearings but it is not a solution for wear in the oil pump.”

So the question still remains about where I got the idea from that I’d read about the technique in a competition preparation manual. I must find that box of books that is temporarily misplaced so that I can provide an answer to that. Meanwhile, one book that I did find was “Tuning BMC Sports Cars” by Mike Garton. This book is from the 1960s, and a note explains that the book first appeared as a series of articles in “Cars & Car Conversions”. Mike is credited as “A technical expert at British Leyland’s Special Tuning Department”. As an aside, I do remember “Cars & Car Conversions” magazine, and I somehow feel that it was perhaps a rather manly publication. I seem to recall that as the sixties’ revolutions were happening on several fronts, the recurring theme of the editorial team was that “real men don’t eat quiche”.

As I delved into Mike’s book, I came across the following mention in the section on the MGB’s engine: “To ensure maximum oil pressure replace the oil pump.. Pack the relief valve spring with two AEH798s (.001 in. thick)”. At last. A mention of packing the oil pressure relief valve spring. But the question still remains of whether one (or perhaps two) “AEH798” was a standard fitment on the MGB engine. I certainly don’t recall seeing two of them on most of the MGB engines I’ve worked on. The other thought I’ve had is that the part numbers for BMC competition parts of the era all started C-. I do recall the competition camshaft that Mike’s book mentions which carries the part number C-AEH770. So this would seem to indicate that “two AEH798s” refers to a standard, non-competition part. I can see there’s still more investigation to do on that particular subject.

We can now turn to the curious question posed in last month’s Myth of the Month. Here’s what I said: “I’m going to ask if you have ever been baffled? If you have, you’ll know what I’m referring to, and if haven’t, aren’t you baffled by the question? So either way, you have been baffled!” The first baffling I was referring to was the baffling of the oil sump pan. The high cornering speed of competition use can cause oil to move across the sump pan and collect and eventually rise up one side of the engine. This movement can be prevented by inserting a baffle into the sump. The baffle is basically a flat sheet of metal with a hole cut in it where the oil pump inlet passes through, and a couple of smaller holes cut in it to allow oil which is draining from the top of the engine to pass back into the sump. With the baffle fitted, the oil stays in the sump under hard cornering forces, and there’s no possibility of the oil pump inlet ever being allowed to run dry. A fairly simple explanation to a potentially baffling question!

TIP FOR THE MONTH We’re going to consider how we can best decide whether we need to modify our engine’s lubrication system. There’s been mention of the old tip of packing the oil pressure relief valve, and it seems the jury’s still out on whether or not that’s a good thing to do. We’ve also looked at the issue of being baffled. But perhaps we should just start with the question “Why make any changes at all?” After all, if the engine manufacturer has specified what’s right for the optimum performance of an engine, who are we to say it needs to be changed? Certainly if an engine is being prepared for competition use, then a different view can be taken. Any modifications would be carried out in order to assist in getting the best performance out of an engine when it’s being subjected to the rigours of competition use, and in addition it would almost certainly be the case that there’d be a set of regulations to abide by. But if the engine was being used on the road, and given the level of safety margins that any engine manufacturer is likely to have built into the design of an engine, I’d say the best course of action would be to leave well alone, and just stick to the manufacturer’s recommendations.

This month’s TOPICAL TIP is a follow up on the subject of March’s Myth of the Month. I’d been relating a discussion we’d been having down at the Chequered Flag about how much protection you had when you bought a second-hand car, and we’d been hotly debating the rights you might have if you’d bought the car from a private seller rather than from a trade outlet.

Well I’m indebted to the consumer organisation “Which” who have the following to say: “You have fewer rights when you buy from a private seller and key parts of the Sale of Goods Act don’t apply – there is no legal requirement for a car to be of satisfactory quality or fit for purpose. But, legally, the seller must: (1) accurately describe the second hand car (for example, an advert must not say ‘one owner’, when the car has had several) and (2) not misrepresent the second hand car (tell you something about the car which isn’t true – such as if it’s been in an accident, the owner must answer truthfully).” So it’s certainly the case that the buyer does have less support from the law if a car’s been bought privately.

So I think I’ll just repeat again that “Caveat Emptor” has always been my personal motto.

And finally, MYTH OF THE MONTH. So there we were pottering down the motorway when the thought for this month’s Myth cropped up. It was a section of motorway that had four lanes, and it so happened that I was driving in the second lane. The Range Rover passed us doing at least seventy miles an hour, which in itself perhaps wasn’t a problem. Then we saw the small two-wheeled trailer being towed along behind the Range Rover. The inevitable murmuring started from the back seat. “He shouldn’t be doing that speed” was the first comment I heard, and my instant reaction was to agree, since I’ve always thought that within “national de-restricted” speed limit areas, towing vehicles were supposed to be limited to ten miles per hour below the speed limit they’d need to keep to if they weren’t towing.

But the next comment didn’t get the same positive reaction from me. “And he shouldn’t be in the third lane” was the opinion that I couldn’t instantly agree with. Within the next half a mile, the inside lane disappeared into a slip road on to another motorway, and this was soon followed by the arrows suggesting that traffic in the second lane should either carry straight on or peel off into the second lane of the departing slip road. I stayed straight on in what was now the inside lane as I’d intended to do, and I was now approaching a slower moving HGV. I indicated and pulled out to the second lane, and in front we all saw that the Range Rover had done a similar manoeuvre, and he was now in the third lane of a three lane motorway.

It’s not often that a group of four from the Chequered Flag all agree, but there was universal agreement at this point. The Range Rover should definitely not be towing a trailer out in the third lane of a three lane carriageway. The incident provided the topic of conversation for the next few miles of the journey. We talked about cars pulling trailers in the outside lane. We were able to agree on the definition of an outside lane. After all, it’s simply the right hand lane on a multi-lane carriageway. We also agreed that a car towing a trailer could use the right hand or outside lane to overtake another vehicle on a two lane carriage. What we couldn’t agree about was whether or not the Range Rover was within the law as he pulled his trailer in the third lane of a four lane carriageway. We did cover the issue around the fact that the inside lane was actually about to effectively disappear as the slip road for the exit to the other motorway started, and perhaps it could be considered that we were travelling on a three lane carriageway with a left hand slip exit lane, but we still had a difference of opinion within our vehicle.

So, who was right? Is it wrong for a towing vehicle to be in the third lane of four, or are my instincts correct, in that the Range Rover driver was okay to be where he was? I think a simple look at the Highway Code will sort this one out, so I’ll do a bit of digging into that one and let you know what I find out next month.
‘Til then...

Safe Driving - Spannerman
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