Leyland 0600 and 0680 Questions.

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Swift
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Leyland 0600 and 0680 Questions.

Post by Swift »

I want to know the history of the 0600, when it came about, what led to it's development and when production ceased.What changes were made to turn it into the 0680. Was it bored out or stroked or both?
Were the power and torque gains extremely significant for this capacity increase?
It seems to me 11 litres (the 0680) is the ideal engine capacity for a full sized bus.

Are the outer dimensions of the 0680 engine block larger than the 0600?
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RK215
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Re: Leyland 0600 and 0680 Questions.

Post by RK215 »

As far as I know the Leyland O.600 engine was developed immediately after World War II. It wasn’t ready in time for the initial post-WWII models such as the OPS1 family, but was the powerplant for the OPS2 family from circa 1947. The horizontal version came out circa 1948.

The O.680 arrived in the early 1950s, vertical then horizontal. Both bore and stroke were increased, from 4.8 x 5.5 inches to 5 x 5.75 inches. As far as I know the block envelopes for the two were the same size.

The O.600 was usually set for 125 hp at 1800 rev/min, sometimes 125 hp at 2000 rev/min. The O.680 was usually set for 150 hp at 2000 rev/min.

The P.680 spark ignition gasoline fuel version was developed by Albion, but cancelled before production began.

In 1960H2 Leyland launched the upgraded Power-Plus versions of the O.600 and O.680, with spheroidal combustion chamber cavities that conferred extra power and greater fuel efficiency. Evidently this was a rather hurried and underfunded development, suggesting that by the late 1950s Leyland wasn't in a position to properly invest for the future.

For the heavy-duty trucks, the O.600S (S for spheroidal) engine, sometimes referred to as the E.600, had the economy rating of 140 hp at 1700 rev/min. Pretty evidently Leyland was competing directly with the Gardner 6LX, which provided 150 hp at 1700 rev/min. The O.680S engine (sometimes referred to as the P.680, P for Power-Plus) was usually set for 200 hp at 2200 rev/min.

The transition to the Power-Plus engines took several years. The Power-Plus designation was not used for the buses, other than the PSR1 Lion, and power and torque settings varied quite a bit.

The super heavy duty truck was swung to the O.680S circa 1962.

The Badger and Retriever medium-weight trucks had the O.600 set for 140 hp at 2200 rev/min, but then these were competing in the same market as the AV470-engined AEC Monarch (Mercury) and Marshal, so a faster running engine was probably appropriate.

The maximum I have seen for the O.600S is something like 165 hp at 2200 rev/min, in a Scammell application.

For the Tiger OPS4 and related Titan bus models, there was a silent transition to the O.600S with no change in power and torque settings. The same happened with the Royal Tiger Worldmaster, with both the O.600S and O.680S engines. But curiously the Lowlander LR, a Tiger/Titan derivative, started with the O.600S set for 140 hp at 1700 rev/min. The Atlantean PDR1 went over to the O.600S with the Mark II version; I am not sure of the power setting.

The Leopard PSU3 (1961) had the O.600S from the start, with settings of 125 hp at 1700 rev/min (bus) and 130 hp at 2200 rev/min (coach). The Leopard L, which had started with the O.600 set for 125 hp at 1800 rev/min, was swung over to the O.600S at the time that the PSU3 arrived. The Royal Tiger Cub RTC1 I don’t know, other than that it started with the O.600 set for 125 hp at 2000 rev/min. But as it was part of the Leopard family, it might have been changed over when the PSU3 arrived.

Then one finds different power settings again with the Panther PSUR1 and later iterations of the Leopard. And then the 690 lightly turbocharged version. Allegedly Ashok Leyland developed an O.750 derivative, but it never saw the light of day.

It is said that the O.600 engine informed Scania practice when it wanted to develop a direct injection engine. Then Scania’s technology swap with Mack – direct injection diesel engine for rear-engined citybus – saw further propagation of the basic Leyland concept. And of course DAF developed the basic O.600/O.680 engine concept much further than Leyland ever did.

I hope that “off-the-top-of-my head” stuff helps for now; I am travelling so don’t have access to the usual references in order to full in the gaps, such as torque numbers, etc.

Cheers.
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Re: Leyland 0600 and 0680 Questions.

Post by mrobsessed »

When this topic came up, you were the person I hoped would find this board again, RK215. This is sure to be interesting.
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Re: Leyland 0600 and 0680 Questions.

Post by RK215 »

Thanks for that. It was dumb luck really; I was sitting in the hotel room here in Singapore killing a bit of time looking at some sites that I don’t often visit these days including this one, and there was the Leyland O.600, O.680 question.

Interesting too is the relative deployment of the O.600 and O.680 engines. On the heavy duty trucks the O.680 was immediately optional to the O.600, and for some export models, was the standard fitting. The medium-weight Badger and Retriever trucks had the O.600 only, though, perhaps because that was at the torque limit for the AEC gearbox that they used. The O.680 was standard on the Worldmaster from the start, with the O.600 optional. The Tiger/Titan/Lowlander never had the O.680 option, perhaps because the 4-speed synchromesh gearbox couldn’t handle its torque. It wasn’t available on the Leopard until 1966, and then only with the Pneumocyclic option, and somewhere around then, maybe a little earlier, it became available on the Atlantean. The Lion PSR1 and Panther had the O.680 option from their respective starts, but in both cases it was the O.600 engine that was featured in the early advertising.

The move up to the O.680 from the O.600 corresponded, more-or-less with AEC’s move up to 11.3 litres from 9.6 litres, although as far I know AEC got there first. For heavy-duty citybus applications, the extra power of the O.680 was needed. A qualitative assessment from the passenger and kerbside viewpoints of the old Auckland fleet was that the Daimler Freelines, with the D650H engine were quite a bit faster in terms of acceleration and hill-climbing than the Leyland Royal Tigers with O.600 engines, although the latter were always mild-mannered and unfussed (and never seemed to suffer from the idle hunting that plagued many Leyland of the period – thinking about it now I wonder if they had non-standard, non-vacuum type governors to better match their AEC preselector gearboxes ). The handful of Regal IVs, with 9.6 litre engines, were decidedly slow and I think were judged as being not well-suited to Auckland requirements. The ERT2 Worldmasters inherited from ABC in the 1970s seemed to be not quite as fast as the Freelines, but then they were bigger buses, at 36 ft overall as compared with 33 ft.

But one could certainly say that the Leyland O.680 defined an engine size, in swept volume terms, and probably in approximate envelope size, that remained a norm for heavy-duty bus applications for maybe three decades or so. The O.680 itself morphed into the L11 and TL11 engines, retaining the same bore and stroke dimensions. Mercedes Benz and MAN both used engines of around 11 litres displacement for their VoV era citybuses, as did Scania and as I recall, FBW in Switzerland during the VST era. Volvo was something of an outlier for many years with its 9.6 litre engine.

And in the late 1940s and early 1950s, the O.600 represented something of a pinnacle in direct injection road vehicle diesel engine design, at a time when many builders were still using less efficient indirect injection combustion systems. For example, Mercedes Benz delayed its changeover to the first part of the 1960s for its “big” (10.8 litre) engine. The Gardner 6LW bettered the O.600 in outright fuel efficiency, but it was viewed as being a bit quirky, and somewhat sensitive to fuel quality.

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Re: Leyland 0600 and 0680 Questions.

Post by Swift »

RK215 wrote: And of course DAF developed the basic O.600/O.680 engine concept much further than Leyland ever did.
Years ago, a truck operator showed me his DAF prime mover approximately late 1980s, early 1990s build and when he revealed to me that the engine was in fact a Leyland 680, I was stunned and couldn't believe it.
It sounded totally different because it had been so refined. I just couldn't reconcile with it being remotely related to the 0680. It sounded like any modern truck engine.

Later on down the track I pulled up next to a similar looking (from memory) DAF prime mover and I could detect a faint 0680 sound as it idled but it was much quieter and smoother as it drove off to the point where any similarities evaporated!!
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Re: Leyland 0600 and 0680 Questions.

Post by User7526 »

And just how good could you tune a 680? We had one of the ex Calabro vehicles at Westbus Penrith years ago with one in it (I can't remember the rego, sorry!). It had a rotary type injector pump and between myself and Alan, we had that thing running so well that we beat Volvos with it! Then there was old 5953, I tuned it and fixed up the worn linkages and it was running just as hard too. Two weeks later they blew up that motor!

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Re: Leyland 0600 and 0680 Questions.

Post by Maladjusted »

Whilst rebuilding some of the Greyhound Pioneer Australia's Bovas which had the DAF 1160 and 1160 ATI Motors, at the Brisbane Transport Workshops engine overhaul section we found there were a very limited number of interchangeable parts from our rapidly depleting Leyland 680 parts supply.
Mainly we found the timing gear thrust plate and gear bushing, & injector rubber washers were about the only parts that were the same and we did use some on rebuilds.
I have got a Power-Plus brochure the 600 and 680 specifications from when the Brisbane Leopards & Panthers were tendered for by Leyland it is dated 1964, should I post it on here?
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Re: Leyland 0600 and 0680 Questions.

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yes
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Re: Leyland 0600 and 0680 Questions.

Post by Froggie »

I just found an old Leyland 0600 at the back of an old bus depot so it was interesting to read your post rk215. It seems the 0600 was ahead of it's time in some ways.
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Re: Leyland 0600 and 0680 Questions.

Post by Swift »

How does the respected 0680 compare in durability to Mercedes compact high revving 11 litre om407h as seen in it's 0305 bus?
Leopards worked alongside 0305s for 12 years (as well as Royal Tiger Worldmasters for about half that) in the P.T.C then UTA of NSW bus fleet.
The MB om447h has a very strong bottom end to cope with the high stresses of stop start work with an automatic transmission and proved to be a legendary engine that just kept going despite years of driver abuse and cutbacks on maintainance.
I think it would have had the edge on the 0680 despite it's harder working life and would have probably given the Gardner 6lxb series a good run.
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Re: Leyland 0600 and 0680 Questions.

Post by gregrudd »

Swift wrote:How does the respected 0680 compare in durability to Mercedes compact high revving 11 litre om407h as seen in it's 0305 bus?
Leopards worked alongside 0305s for 12 years (as well as Royal Tiger Worldmasters for about half that) in the P.T.C then UTA of NSW bus fleet.
The MB om447h has a very strong bottom end to cope with the high stresses of stop start work with an automatic transmission and proved to be a legendary engine that just kept going despite years of driver abuse and cutbacks on maintainance.
I think it would have had the edge on the 0680 despite it's harder working life and would have probably given the Gardner 6lxb series a good run.
The Gardner 6LXB was from my understanding the preferred engine of UK operators. I often wonder how popular Gardner was in Australia when it came to buses. My father who was driving British Trucks in the late 50's early 60's said that Gardner was definitely well regarded (Probably for fuel efficiency) before American diesels became common place. From what I understand most American Trucks used in Australia in the 50's/early 60's were actually petrol powered.
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Re: Leyland 0600 and 0680 Questions.

Post by boronia »

Gardeners were usually only found in "niche" chassis like Foden, Atkinson, Seddon, Daimler, and some pre-war Albions. Mainstream chassis like Bedford, AEC and Leyland simply offered their own proven engines, and made Gardener options too expensive to consider.

Petrol prices in USA were so low that any cost benefits of diesel fuel did not match the extra costs of using the engines. Early American diesel engine were designed for highway use, running continuously; they did not stand up well to stop/start driving.
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Re: Leyland 0600 and 0680 Questions.

Post by Guy_Arab »

boronia wrote:Gardeners were usually only found in "niche" chassis like Foden, Atkinson, Seddon, Daimler, and some pre-war Albions. Mainstream chassis like Bedford, AEC and Leyland simply offered their own proven engines, and made Gardener options too expensive to consider.

Petrol prices in USA were so low that any cost benefits of diesel fuel did not match the extra costs of using the engines. Early American diesel engine were designed for highway use, running continuously; they did not stand up well to stop/start driving.
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Re: Leyland 0600 and 0680 Questions.

Post by riverbank54 »

boronia wrote:Gardeners were usually only found in "niche" chassis like Foden, Atkinson, Seddon, Daimler, and some pre-war Albions. Mainstream chassis like Bedford, AEC and Leyland simply offered their own proven engines, and made Gardener options too expensive to consider.

Petrol prices in USA were so low that any cost benefits of diesel fuel did not match the extra costs of using the engines. Early American diesel engine were designed for highway use, running continuously; they did not stand up well to stop/start driving.
That's interesting. How would torque and power graphs compare to a diesel designed for start and stop then? I would think the clutch would have to be tougher too.
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