ramone:
In your opinion do you think this engine could have been modified successfully?
Anything’s possible! They had the crank bearings sorted, according to the bloke that Gingerfold spoke to. Let’s assume that a bigger radiator would have cured the overheating. Earlier mention of running at a fast idle helped to cool an overheating engine suggests a slightly higher flow rate from the water pump would not have gone amiss. There would have been endless combinations of possible modifications. The only big hurdle was the small capacity- 14 litres would have been ideal, so it could sit above the TL12 in the range. Leyland would have preferred to make their own engine, rather than give their own wages to ■■■■■■■■ If there was a deciding factor in the demise of the engine, it was the size of it. The build quality/industrial relations issues affecting Leyland cannot have helped the engine’s cause. It would have been a brave decision to trust a problematic project to those factories.
And as mentioned putting it in the Marathon which would allow better air flow and could accomodate a much larger radiator … if only
Only a quick one, and I need my tea, and my Bollinger!!
More due to incompetence, than design error. The original failings were traced to a “machine error”. The engine was not a bad design, and certainly in keeeping with the " current " thinking, (right or wrong though that may have been).
It did need more cooling, but I am convinced thet it was not envisaged to sit under such a restrictive enviroment as the Ergomatic cab.
Overall it was a good design, (of its time), equally as good as the early Berliet V8, and also that of Unic, and given true chance could have become a European leader.
gingerfold:
Someone who worked for the Ricardo engine consultancy was convinced that the piston speed of the V8 was right on the limits of what was achievable reliably at the time, but I didn’t understand what he was on about as I’m not an engine designer.
Regarding piston speed, I have compared the AEC V8 to the similar Mercedes OM402. I do not have the conn. rod lengths for either engine, but have worked out maximum big end speed, for the sake of a rough comparison. The Mercedes had its maximum power at 2500rpm, the AEC 2600. The Merc’s stroke was 130mm, against AEC’s 114mm. The maximum speed of the big end of the Merc comes out at 17m/s and the AEC is actually slower, at 15.5m/s. If we do it properly, using the conn. rod length, piston speed is also a function of the ratio of rod length to stroke so, if the AEC had a short rod in relation to its stroke, compared with the Mercedes, then the difference between the two would be smaller, possibly even favouring the Mercedes. Either way, the piston speed of the AEC was probably a bit slower than the OM400 series Mercedes, about which engine’s reliability a bad word has never been uttered!
If anyone expresses an interest in these futile retrospective calculations, I will do them properly, and try to find the corresponding data for other comparable V8s of the period- the ■■■■■■■ VINE, Deutz 413 and Berliet 825, maybe even the Unic and Fiat, if the dimensions can be found.
Yes, they were ‘top hat’ design dry liners in both capacity engines.
Do you reckon, having looked at the cylinder block and liners, that it could have stood another increase in the bore, without making the liners or the walls of the block too thin? If it could have been stretched to 14 litres, I think it might have been worth Leyland carrying on with it.
Sorry for the late reply to this, but in my opinion no.
It is my belief that the original 12.1 litre blocks had been bored to their limit with the 13.1, and expanding the capacity further would have left the cylinder walls too thin. An increase to 14.1 would have required a 10.00mm over-bore from the original 130.00mm bore size.
The change over from imperial to metric from prototype to production has been touched on.
Speaking as someone who has stripped both prototype and production units, the only metrification of the production units that I am aware of is in some of the threaded fixings. The bore size for example was 130.00mm on the 740 prototype, and was 130.00mm in production 740’s. Bearing sizes, valve lift, stroke etc were all metric values (and identical to production) on the prototype that I had experience of.
What is interesting is that both the block and head castings were different.
The prototype blocks had much smaller water gallery casting cores resulting in a narrower water passage, for production it was enlarged substantially and the enitre gallery along both banks covered by detachable steel plates. The heads were also altered to allow fitting of a single rocker cover per head, rather than the twin covers of the prototype.
Both these changes required casting pattern and tooling changes, so it rather begs the question why some of the other failings were not re-tooled at this time too?.
ERF:
…What is interesting is that both the block and head castings were different.
The prototype blocks had much smaller water gallery casting cores resulting in a narrower water passage, for production it was enlarged substantially and the enitre gallery along both banks covered by detachable steel plates. The heads were also altered to allow fitting of a single rocker cover per head, rather than the twin covers of the prototype.
Both these changes required casting pattern and tooling changes, so it rather begs the question why some of the other failings were not re-tooled at this time too?.
This is fascinating stuff. I guess that, to change one pattern (for the water gallery) would not incur a great cost, as long as the core still attached to the rest of the cores in the same way, IE with minimal modifications required to the other patterns. The same applies to the top face of the head. Again I am guessing, but the gallery enlargement would have been the fix for the overheating. To address the crank journal size would have meant increasing the bore spacing, which would entail a longer block. To increase the stroke would have meant a larger diameter internal surface in the crankcase, to clear the conn. rods. The distance from the crankshaft centreline to the top face of the block would have to increase, to allow for the longer stroke and probably longer conn. rods. In other words, it would have been a start-from-scratch job, including all the design work, right back to the stress calculations on the crankcase.
If no increase in the bore was possible, then the capacity was stuck at 13.1 litres. The mooted 350bhp turbocharged version would have had more power per litre than anything else at the time, apart from the boiling Pegaso engine I mentioned earlier. Of course, a decade later, such a specific power output would be considered normal, but in 1973 (Marathon launch), it would have taken some courage to produce such an engine.
If AEC had taken the high-torque-rise route pioneered by Mack, they might have had a winner. However, no company apart from Mack made a decent job of that idea until the late 1970s, so this is just hollow speculation!
Good stuff. Interestingly AEC had always quoted metric bore and stroke dimensions in mm ever since it built its own engines in the 1920s when it acquired Tyler engine company which had supplied engines for the acclaimed AEC Y-Type that served in WW1. Just as the Leyland 500 series was designed for compactness and light weight, so too the AEC V8. Why the British lorry makers had this obsession with compactness and lightness in the 1960s is hard to comprehend when there was an increase in gross vehicle weights of 6 to 8 tons applicable from 1965 and a corresponding increase in vehicle lengths. The weight saving of a couple of hundredweight on an engine was insignificant in the overall picture, especially so if it had resulted in a reliable and robust engine from a larger unit.
gingerfold:
Good stuff. Interestingly AEC had always quoted metric bore and stroke dimensions in mm ever since it built its own engines in the 1920s when it acquired Tyler engine company which had supplied engines for the acclaimed AEC Y-Type that served in WW1. Just as the Leyland 500 series was designed for compactness and light weight, so too the AEC V8. Why the British lorry makers had this obsession with compactness and lightness in the 1960s is hard to comprehend when there was an increase in gross vehicle weights of 6 to 8 tons applicable from 1965 and a corresponding increase in vehicle lengths. The weight saving of a couple of hundredweight on an engine was insignificant in the overall picture, especially so if it had resulted in a reliable and robust engine from a larger unit.
The British “compact” obsession does seem peculiar. If you read the Commercial Motor show report in the 2nd October 1964 issue, starting at page 100, it is all laid out in gory detail. They appear to turn their noses up at the Mercedes LP, because of its high floor then, on the next page, state that compact, high speed engines will be required, to cater for the demand for more power without having a large engine cover in the cab! What was so bad about the driver having to climb one extra step, for God’s sake? This should not have affected AEC, with their enthusiasm to satisfy their export customers. I detect the dead hand of Mr. Stokes, and his decision to leave the Continental markets alone, forcing AEC down the British small cab/compact engine route. Oops, my own personal obsession has just reared its ugly head!
Weight saving is another matter. You can flog it to your customers as an advantage, however minor that may be. More importantly, it saves material cost. I once spoke to a well-seasoned purchasing manager, who gave me a rough rule of thumb for the design of mass-produced structural parts. He told me guideline prices for cast iron, cast steel and forged steel parts, ex works- all in pounds per ton! As a very rough guide for any process, price the material ex stock, double it and add 10%! Even at the prototype stage, material cost is significant. A typical CNC machinist might charge £35/hour. For a small batch of parts, the order might spend an hour in the office, an hour setting up and an hour making swarf. In that last hour, the machine may well chomp through hundreds of pounds’ worth of steel.
There was a Scammell Crusader wid the AEC V8 800 Mandator engine complete wid much bigger radiator and header tank ect , still no good though , but it took Scania a few years to get its V8 right , thats why Volvo stayed safe wid only straight six diesels , an just develope old designs it good engineering law .
Hiya…i’ve seen a Scammell crusader in a book saying the AEC V8 was an available engine, i can’t remember ever seeing one.
i see your point though thinking the larger radiator and certainly more flow of cool air under the higher cab… good question.
maybe for some reason the V8 still failed or we would have seen many Scammells with the AEC fitted. i think a Perkins was
trialed. it seemed a must as Scammell went with the Detroit vee engine.i know the Rolls was a winner in the Crusader.
John
The Scammell Crusader was developed a few years after the Mandator V8. Originally in the Crusader’s design brief the AEC V8 was to be an engine option in the Crusader but when the Crusader was signed off for production AEC V8 production had been suspended because of its unreliability, and Leyland pulled the plug on the engine even though a reworking into the AV800-V8 was giving much improved reliability. By then Leyland heirarchy was in panic mode with the failures of its other flagship engine programme, the famous “headless wonder” 500 series.
With the engines options available for the Crusader there was no reason to offer the TL12 in the Crusader as well, bearing in mind that the TL12 wasn’t available until 1974 and at that stage the Crusader was only being sold in relatively small numbers into the general civilian market.
Scamell realised early what Leyland eventually realised too late in that natural selection,using outside engine suppliers,was better than trying to stick with Leyland and AEC designs.Natural selection in this case simply being that Rolls could provide better 6 cylinder and Detroit better V8 engines respectively than Leyland/AEC.
Carryfast:
Scamell realised early what Leyland eventually realised too late in that natural selection,using outside engine suppliers,was better than trying to stick with Leyland and AEC designs.Natural selection in this case simply being that Rolls could provide better 6 cylinder and Detroit better V8 engines respectively than Leyland/AEC.
And thats why the Crusader became the best selling tractor unit in the UK for many years to come
Carryfast:
Scamell realised early what Leyland eventually realised too late in that natural selection,using outside engine suppliers,was better than trying to stick with Leyland and AEC designs.Natural selection in this case simply being that Rolls could provide better 6 cylinder and Detroit better V8 engines respectively than Leyland/AEC.
And thats why the Crusader became the best selling tractor unit in the UK for many years to come
What a coincidence that this topic has resurfaced at this time. I have just received my copy of the AEC Bulletin (produced by Robert Harris) and it has quite a lot of info about the development testing of the AEC V8 engine. One lengthy article by a boffin from at The University of Southampton’s Institute of Sound and Vibration Research is totally beyond my comprehension with its scientific data (if anyone with good brain would like a copy please pm me), but picking out what I can from it there is a wealth of information about V8 diesels in general. The AEC V8 did have noise issues, it was a noisy bugger and even louder than a fixed head Leyland 500 on test at the same time. Basically, an oversquare high revving V8 was always going to be a problem irrespective of noise considerations. The thinking of the 1960s in this respect was completely wrong. Scania got it right with its long stroke, slow revving (relatively speaking) V8. Its amazing what comes to light all these years later. Rolls Royce was also developing a V8 diesel for truck applications.
Another article in the same magazine also confirms that the turbo-charged AEC V8, previously thought only to have been a 350 bhp test bed engine was actually installed into one of the 6x4 Mammoth Major V8s (the red ‘G’ registered one). I quote from the author " I can positively confirm that unladen, in the hands of Tony Rice, the AEC Experimental Fitter, the 350 bhp V8 Mammoth Major tractor with the epicyclic 10-speed splitter gearbox could certainly out-accelerate all passenger cars from the traffic lights on the roads between Leavedsen and Windmill Lane."
gingerfold:
… One lengthy article by a boffin from at The University of Southampton’s Institute of Sound and Vibration Research is totally beyond my comprehension with its scientific data (if anyone with good brain would like a copy please pm me), but picking out what I can from it there is a wealth of information about V8 diesels in general…
I tried to send you a PM, but it seems to be stuck in my Outbox. Bloody computers. If you do not get the PM, please (somehow) send me a copy of the report, because I would love to read it.
Never was or will be a good v configuration diesel engine,or petrol for that.too short of a stroke is biggest problem.long deep strokes are what is necessary.I only ever had 1 and that was a mastiff.biggest load of (zb) ever made.
gingerfold:
What a coincidence that this topic has resurfaced at this time. I have just received my copy of the AEC Bulletin (produced by Robert Harris) and it has quite a lot of info about the development testing of the AEC V8 engine. One lengthy article by a boffin from at The University of Southampton’s Institute of Sound and Vibration Research is totally beyond my comprehension with its scientific data (if anyone with good brain would like a copy please pm me), but picking out what I can from it there is a wealth of information about V8 diesels in general. The AEC V8 did have noise issues, it was a noisy bugger and even louder than a fixed head Leyland 500 on test at the same time. Basically, an oversquare high revving V8 was always going to be a problem irrespective of noise considerations. The thinking of the 1960s in this respect was completely wrong. Scania got it right with its long stroke, slow revving (relatively speaking) V8. Its amazing what comes to light all these years later. Rolls Royce was also developing a V8 diesel for truck applications.
Another article in the same magazine also confirms that the turbo-charged AEC V8, previously thought only to have been a 350 bhp test bed engine was actually installed into one of the 6x4 Mammoth Major V8s (the red ‘G’ registered one). I quote from the author " I can positively confirm that unladen, in the hands of Tony Rice, the AEC Experimental Fitter, the 350 bhp V8 Mammoth Major tractor with the epicyclic 10-speed splitter gearbox
could certainly out-accelerate all passenger cars from the traffic lights on the roads between Leavedsen and Windmill Lane."
not bad . considering it was up against a Hillman Imp,an Austin A30 and a Daf variomatic fastback.
I belive J Coates (HGV Services) Ltd of Leicester ran one in their driving school arm. I Joined them in 1973 & it had gone by then, only heard it mentioned. I know the RTITB had one, useful because of its 3 seats. John had close connections with Ford & Slater (still in existance) so may have sourced it through them. I have no idea of the number.
