I was hoping that you would tell me what BS 649 was. However, it appears that it was a measure of “The Performance of Reciprocating Compression Ignition Engines Utilising Liquid Fuel Only”. There were BS 649 standards for 1935, 1949, and 1958 and this standard was specifically for non-automotive applications, such as industrial generating sets, and auxiliary marine engines.
I had a quick look, and BS649 seems to be the standard for boats and generators. The Leyland 690 is some 12% less powerful than in its automotive guise, for some reason. Boats are usually more powerful. Maybe Leyland chose to set the engine at a lower BMEP throughout, for their own reasons? The standard is hidden behind a paywall, as are all British Standards. That refers back to my previous post, in that the BS merchants are kept at bay by that restriction. Unfortunately, I guess that group also includes us, in that regard at least!
gingerfold:
This torque chart shows the difference between the various standards ratings, if CF can be bothered to look at it. It’s for the Leyland 690 engine, but it clearly shows the differences in the various ratings.
0
Thanks gingerfold.Yes agreed they certainly seem like surprisingly disparate standards of measurement.Especially when comparing figures like the ■■■■■■■ 335 at AU 141 with what it,let alone the 350,would have been rated at under SAE gross.Although strangely I’ve never actually seen any figures stating more for it than its 141 rating. 
However as I’ve said the Rolls Eagle Mk2 and 3 are valid reference points for the specific point that I’m making.IE you just ain’t going to be able to develop the 13.1 litre AEC V8 significantly any further than 638 lb/ft ( AU 141 standard ) without breaking it with the smaller capacity Eagle containing way more potential and capacity for development than that.Which seems to have been confirmed by what actually happened next.IE not that they ‘didn’t’ develop it they ‘couldn’t’ because it was predictably already suffering from end bearing issues even at that rating let alone more.
The obvious question then is what was the difference which made the Eagle able to stand up to going way past 100 lb/ft per litre but the AEC V8 failing at less than half that ?.
AEC V8 Engine Restoration - Part Three.
(Part two is on page 33, if anyone lands here and is looking for it).
Now seems a good time in proceedings to look at the next phase of the engine restoration.
Some of the following illustrations are from the AEC V8 service training course, hosted at the BL service training centre at Standard Triumph, Radford.
We have just been discussing power ratings and power delivery, and this is one area where the AEC V8 engine did actually get a good deal of innovative development in the early stages of it’s conception. It had an exceptional power output for it’s time, ably described by every lorry driver lucky enough to drive a Mandator V8 in service.
But why?.
There are a couple of key paragraphs in the three-page CM article that I posted a few pages back, the first is…
So how was that possible?.
The first key to this was AEC being among the direct injection engine manufacturers of the early 1960’s to employ Toroidal Cavity pistons and masked inlet valves. In basic terms, the Toroidal combustion chamber in the piston top improves the way in which air and injected fuel mix, and therefore burn more intensely, releasing more power from the process, also improving efficiency. (If anyone can describe it better, please do!)
The overall combustion process itself is the key thing that engine development engineers are always trying to improve, and one of many ways of doing that was by masking the inlet valves. The mask is a small curved section of the inlet valve head that protrudes up into the port.
You can see it on valve ‘B’ here…
This mask has the effect of inducing turbulence or ‘swirl’ to the air being drawn into the cylinder on the induction stroke, allowing more air to enter the cylinder and again giving an improved mix ratio for the compression to ignite once the atomised fuel is injected.
I’m trying to keep this simple, honest!.
For this to work, the inlet valve cannot be allowed to rotate in the way that a valve normally can in an engine, so the stem of the valve is splined and a special cap is fitted to the top of the valve guide to keep the valve mask in exactly the right position to achieve the best possible combustion results. This can be seen here…
I was lucky with engine 316 because I had actually managed to find new old stock valves, so this was one area of the engine that didn’t cause me great problems, but of course it couldn’t last, and the next component in line was a major headache - the camshaft.
By this time, during the course of this restoration, we had stripped down four AEC V8 engines, one of which was an original low mileage unit. The original camshaft in engine 316 was in horrendous condition, out of the 16 cams only 4 still had the ends of the lobes intact. The others all had wear up to 6 mm - a colossal amount for a cam lobe tip to loose, obviously well through the case hardening.
We looked at the cams in the other engines, but they were ALL worn, even the low mileage one, although to a much lesser degree. The cam followers were the same, where the lobes had worn down, the associated followers were all badly grooved as shown here…
But why?.
The conclusion was that the followers are designed to rotate, thus spreading the wear evenly across the contact surface, but it was obvious that most of the followers in all of these AEC V8 engines hadn’t been rotating at all, which was very confusing. So we now had a major problem. I couldn’t put 16 serviceable cam followers together from 64 recovered from all the stripped engines, and I had no good camshaft. Bearing in mind that British Leyland had withdrawn spares support for the AEC V8 engine completely by 1976, I stood no chance of finding new parts. I made a call to Simon Smart at Automotive Services in Northampton to see if he had any ideas, and luckily he did!. “Bring me your best parts” he said, so over I went with the 24 best cam followers and the 2 best camshafts.
After a lot of surface testing and measuring, the best followers were selected to be reground, and the best camshaft sent off to Kent Cams for re-grinding. Now, anyone who has had a Ford car in their youth is probably aware of Kent Cams from their connection to motorsport, but up until this point I didn’t realise that they are one of the few UK firms that specialise in ALL engine camshaft’s, whatever the application.
I had two questions - what would this all cost?, and how can you grind material OFF a worn cam to restore the original lift?.
The first answer was encouraging. “As it’s a 1960’s Diesel engine, both inlet and exhaust cam profiles will be identical” they said. “And if we’ve got a known master profile on the shelf, you are just looking at the machining and re-hardening costs, so circa a couple of hundred quid”.
All good so far.
The second answer was rather obvious when you think about it. Grinding material off the BACK of the cam enables the material at the front to be profiled back to completely the original shape, with no detriment at all - as long as there is sufficient unworn material left on the cam, and ample adjustment on the rocker arm valve clearance adjustment screws to take up the difference, which there easily was.
Then I got the usual AEC V8 phone call.
It was Kent Cams.
“There is a problem with this camshaft”.
They had done a lobe profile analysis on the cams with no wear, and found two things of interest. The inlet cam profile was very different to the exhaust, and neither profile matched ANY of the hundreds of master profiles used for grinding held in their huge library!.
Great.
The clue to this was actually in the CM launch article…
So now I was faced with the increased cost of having TWO master profiles specially made for the grinding machine, just to get one camshaft re-ground!.
That’s AEC V8’s for you.
Kent Cams did come through though, and a fully reconditioned camshaft and followers (including some spares) duly arrived back with me…
The other thing Kent Cams said was that, contrary to modern practice, the tips of the AEC cam lobe were straight - ie parallel to the shaft.
Now I thought all cams were made like that, but apparently not. Cam tips these days have a very slight taper of only a few thou machined into them, which mates with a very slightly concave surface on the follower. The two are then positioned slightly off-centre to each other to promote the follower to turn every time the cam strikes it.
In the AEC V8 engine the followers are all completely flat, the cam tips are parallel to the camshaft, and the cam strikes the follower at exactly the centre point. Other AEC engines have the flat cam tips and flat followers, but do have the two off-set slightly to promote rotation.
So why build an engine like that, knowing full well that the follower would not turn at all if just a little sticky oil or carbon got near it?.
The answer actually came from Perkins.
“That was quite normal when we were working on development engines in the 1960’s, trying different cam profiles and testing prototypes…” they said!.
So, all the hard development work had been done on the innovative cam profiles early in the AEC V8 development, but when the project was shelved, the finer detail of the cam and follower relative positioning still hadn’t been finalised.
If details like that had been allowed through before production started, what else would we find?.
One thing was quite shocking really.
Positioned over the top of the cam followers is a retainer plate with holes for the push rods to pass through, shown here…
The idea is that it acts as an oil baffle, and stops the followers from being pulled out by suction if the push rods are removed. In the prototype engine that I stripped, the push rod holes in this plate were all in slightly the wrong place, and had all been hand filed to an oval shape to clear the push rods.
When we looked in all of the production engines, the push rods were actually rubbing on it!.
In two engines we even found that the push rods were in fact bent, and would pass through the centre of the hole, but when rotated would lay against one side of it.
Can you imagine this?. An engine in production with such basic things yet to be sorted out.
What must the people assembling them have thought?.
Why was it not addressed?.
Keith Roberts and his team must have stood in complete disbelief at Southall watching machine tools being set up to produce an engine with such fundamental simple flaws still in it’s design, let alone the major issues that they knew it still had.
I don’t really like to speculate, but to me it is just as though a production set up team had burst into the AEC R&D department, taken all the prototype V8 files and drawings away, and began tooling up to manufacture the engine - whatever the R&D team said in protest!.
[zb]
anorak:
Regarding SAE, I have a question for all- there appear to two SAE gross standards:
This would account for the big difference in the French ratings, but not the American ones.
There’s also SAE Net after 1971.
However no seeming figures much if any higher than AU 141 ratings for the 335 anywhere.Which logically would have been stated at SAE Gross in the home market at the time ?.
Interesting. Masked inlet valves were used in Gardner and BMC 3.4/3.8 and 5.1/5.7 engines, and probably more, and I wonder if they are still fitted in modern diesels or were they just something that were not considered worth the extra expense regarding machining etc as they contributed little to performance? Cam follower suction was also an issue with many engines, experienced fitters soon learned to twist the pushrods to break the oil film before removing pushrods as either engine sideplate (or in some cases) sump removal to retrieve errant followers wasn’t something you wanted to do more than once! 
Pete.
Fascinating stuff^^^
- You would have thought that simply offseting the centreline of the cam, axially down the shaft, from the centre of the follower, would promote the desired rotation. Not so, apparently.
- The wear on the knackered follower shown in the photograph looks excessive, even without the desired rotation. Maybe there was an issue with high lobe-follower contact loads, or bad material/heat treatment?
- The issue of the plate/pushrod fouling reminds me of a comment (credit gingerfold, possibly) mentioning AEC factory practice being that the shopfloor staff would solve problems themselves, unrecorded, without informing the engineers. This looks like an inevitable failure of that “system”.
As an aside, I once worked, as a sub-contract designer, on a system which required the follower to be kept in the same orientation, for a reason irrelevant to this discussion. IIRC, the thing that I drew had a pin stuffed into a groove, to stop it rotating. This tells us that non-rotating followers is not the end of the world. Of course, the ones I worked on might have been harder than usual material, or someone had found out that modern oils allowed the condition, or maybe the thing never made it to production!
Did you find that any of the pushrod male or female ends were loose or badly worn? I usually find at least three ends have unsoldered every time I have the pushrods out of an AEC engine. That baffle plate makes life interesting recovering the bottom end because oil suction often prevents removing it with a magnet. That means the tappet chest cover has to come off, which is not easy in a half cab when it is tight against the firewall. The bonding or sealing between the dome washer and the cover has often failed which is why the thing pukes oil.
Masked inlet valves and toroidal cavity pistons. I’ve always been led to believe that these design features were fundamental to the very good starting characteristics of AEC engines, even in the coldest weather.
Carryfast:
In which case even by those {torque} figures if piston area is worth more than leverage the difference between the Perkins v AEC would be expected to be a lot closer to the difference in bore size ( well over 20% ) than just 16%. {torque}
In just that one statement you demonstrate your complete lack of understanding for Diesel engine dynamics.
To help with your maths again - 108 mm to 130 mm is 20.37%.
Is that “well over 20%” in your world?.
Carryfast:
The obvious question then is what was the difference which made the Eagle able to stand up to going way past 100 lb/ft per litre but the AEC V8 failing at less than half that ?.
That question has been answered in detail so many times over these pages.
I really do give up now… 
windrush:
…Masked inlet valves were used in Gardner and BMC 3.4/3.8 and 5.1/5.7 engines, and probably more, and I wonder if they are still fitted in modern diesels or were they just something that were not considered worth the extra expense regarding machining etc as they contributed little to performance…
They contributed a huge amount to Diesel engine performance, but these days the ‘swirl’ is usually induced to the intake air by moving variable flaps located within the inlet manifold.
[zb]
anorak:
Fascinating stuff^^^
- You would have thought that simply offseting the centreline of the cam, axially down the shaft, from the centre of the follower, would promote the desired rotation. Not so, apparently.
- The wear on the knackered follower shown in the photograph looks excessive, even without the desired rotation. Maybe there was an issue with high lobe-follower contact loads, or bad material/heat treatment?
- The issue of the plate/pushrod fouling reminds me of a comment (credit gingerfold, possibly) mentioning AEC factory practice being that the shopfloor staff would solve problems themselves, unrecorded, without informing the engineers. This looks like an inevitable failure of that “system”.
As an aside, I once worked, as a sub-contract designer, on a system which required the follower to be kept in the same orientation, for a reason irrelevant to this discussion. IIRC, the thing that I drew had a pin stuffed into a groove, to stop it rotating. This tells us that non-rotating followers is not the end of the world. Of course, the ones I worked on might have been harder than usual material, or someone had found out that modern oils allowed the condition, or maybe the thing never made it to production!
I’ll see if I can find one of the worst old followers to photo, but they were horrendous.
Getting on for a 2 mm deep groove worn in the surface.
This is another one of those cases where correcting the underlying simple problem is impossible without making major component changes, but it is the general consensus of opinion that modern oils will reduce the effects significantly, as you say.
cav551:
Did you find that any of the pushrod male or female ends were loose or badly worn? I usually find at least three ends have unsoldered every time I have the pushrods out of an AEC engine…
Yes!. We struggled to get 16 perfect pushrods out of the 64 available, but we did manage it!
ERF:
Carryfast:
In which case even by those {torque} figures if piston area is worth more than leverage the difference between the Perkins v AEC would be expected to be a lot closer to the difference in bore size ( well over 20% ) than just 16%. {torque}In just that one statement you demonstrate your complete lack of understanding for Diesel engine dynamics.
To help with your maths again - 108 mm to 130 mm is 20.37%.
Is that “well over 20%” in your world?.Carryfast:
The obvious question then is what was the difference which made the Eagle able to stand up to going way past 100 lb/ft per litre but the AEC V8 failing at less than half that ?.That question has been answered in detail so many times over these pages.
I really do give up now…
I was going by the 13.1 litre engine’s 135 mm bore and 638 lb/ft AU 141 1967 figure ‘including’ any test standards differences. Apologies if I’ve confused that with the 12.1 litre 580 lb/ft figure although even that conparison is still more than a 20 % difference in bore size regardless.
While no the question as to how you’re going to increase,the AEC V8’s torque output,without breaking it,hasn’t been answered because it can’t be answered.With development and production of it predictably and unarguably having stalled then halted at 638 lb/ft and less than 50 lb/ft per litre to AU 141 1967 standard.
With the Rolls Eagle only going ever upwards from that figure including AU 141 1971.As for the Scania V8’s output with just a 127 mm bore don’t even go there.
My two penance on Camshaft wear,which ive seen my fair share of, with my involvement with ■■■■■■■■
1,Valve recession due to soft seats leading to valve clearance issues,basic engineering.
2,Bad top end sets.
3,Outer base profile with too sharp lift and drop off profile ultimately leading to seat and stem failures.
4,Bottom end failures due to oil pump being destroyed from Camshaft material mixing in the lube oil.
gingerfold:
Masked inlet valves and toroidal cavity pistons. I’ve always been led to believe that these design features were fundamental to the very good starting characteristics of AEC engines, even in the coldest weather.
The chamber was really introduced to reduce piston rock and promote the flame to burn in the centre of the piston directly over the conrod.The masked valve idea was/is a success.Even todays car diesels use the basic idea in the form of swirl flaps and nowhere as reliable as the AEC idea.
Does anybody have a coolant flow diagram of a 740/800 as I,d be interested to see it.
railstaff:
My two penance on Camshaft wear,which ive seen my fair share of, with my involvement with ■■■■■■■■1,Valve recession due to soft seats leading to valve clearance issues,basic engineering.
2,Bad top end sets.
3,Outer base profile with too sharp lift and drop off profile ultimately leading to seat and stem failures.
4,Bottom end failures due to oil pump being destroyed from Camshaft material mixing in the lube oil.
Yes, your point 1) was something we have seen too, but none of the AEC V8 engines were exhibiting any sign of it.
Point 3) is an interesting one, which ■■■■■■■ engines suffered with it?
You would think it should be detected during very early engine testing, as it would surely affect every valve?
railstaff:
Does anybody have a coolant flow diagram of a 740/800 as I,d be interested to see it.
So would I!
Even having stripped and examined these engines it is still a puzzle working out the flow.
I have all the AEC technical literature for the V8, but none of it contains a coolant flow diagram.
ERF:
railstaff:
My two penance on Camshaft wear,which ive seen my fair share of, with my involvement with ■■■■■■■■1,Valve recession due to soft seats leading to valve clearance issues,basic engineering.
2,Bad top end sets.
3,Outer base profile with too sharp lift and drop off profile ultimately leading to seat and stem failures.
4,Bottom end failures due to oil pump being destroyed from Camshaft material mixing in the lube oil.
Yes, your point 1) was something we have seen too, but none of the AEC V8 engines were exhibiting any sign of it.
Point 3) is an interesting one, which ■■■■■■■ engines suffered with it?
You would think it should be detected during very early engine testing, as it would surely affect every valve?railstaff:
Does anybody have a coolant flow diagram of a 740/800 as I,d be interested to see it.So would I!
Even having stripped and examined these engines it is still a puzzle working out the flow.
I have all the AEC technical literature for the V8, but none of it contains a coolant flow diagram.
M11 suffered with valve train problems.Considering the amount in service,the percentage was low.But none the less seat recession was present on every one.Clearly the compression (jake) brake didn’t help matters which was the reason for delaying its operational start point until the lube oil had reached a set temperature.
Someone,somewhere must have a diagram.
From the rear of the waterpump how is the coolant distributed into the block.Does it go through the right bank,through the rear pipework into the left bank and up through the heads respectively.
I cant be sure,but looking at the previous picture of half a v8 it appears to have “end to end” cooling,by this I mean the coolant doesn’t pass through the block deck into the heads.Im I right?
railstaff:
I cant be sure,but looking at the previous picture of half a v8 it appears to have “end to end” cooling,by this I mean the coolant doesn’t pass through the block deck into the heads.Im I right?
No, there are 5 large and several smaller passages between each block deck and head.
There are end connections in each head (and the rear of each bank of the block) which are used to pass the coolant from one side to the other via the external transfer pipes.
There isn’t even a coolant flow diagram contained in the service training slides from the BL course designed to train fitters on the engine. There are plenty of oil flow diagrams, but all you get coolant wise is a slide showing the components.
A good clue to the circulation is in the CM launch article, which basically corresponds with how I perceive it to work…
It’s interesting to note the comment in there on block water passages, because too close spacing of cylinder centres within a block is a noted cause of piston skirt scuffing, and that is another problem that the AEC V8 in all of it’s capacities suffers from. Yet another problem that would not have existed if the block had been just a few centimeters longer.