AEC V8

[erf]

Now seems a relatively good point to start the restoration story of the AVM8-740 engine in the video above.

Part One.

This is engine number 316, a relatively late build from very late in 1969. It is the original engine as fitted to my Mandator V8 chassis when it was built, and was alternated and rebuilt together with a prototype V8 engine at major overhaul intervals by the original operator to keep the vehicle on the road. This system lasted until it hauled it’s very last load in 1977, at which point the prototype unit was installed and engine 316 had ‘alledgedly’ been rebuilt ready to fit and then stored - this turned out to be far from the case.

This is engine 316 exactly as it was removed from it’s dry storage by me back in 1991 (although this is a 2015 photo)…

The stripdown began in May 2015…

…and revealed many horrors, including lots of evedence of various pistons ‘picking up’ on the liners due to overheating, and the liner cracking issue described above…

All the bare castings were then sent over to SPL at Dudley to be completely stripped clean of any rust and paint. This is a very sophisticated chemical process that removes all contamination, inside and out, but crucially does not remove any sound metal. The process is used by Catapillar and the MoD amongst others in the course of reconditioning their large engines. The photo here is on arrival at SPL…

The cleaned block and heads were then sent over to Ivor Searle Ltd., a long established engine reconditioning machine shop based in Soham. We knew the liners were all scrap, but with no replacements available anywhere it looked like we had hit our first major hurdle. Working on the widely accepted information (wrongly) that the AV740 liners were thicker walled than AV800/801 items, we searched the world for suitable liners, and found a supplier in Australia with ten liners in stock that he was sure were for the AV740 AEC V8. The liners he had were thicker than AV800 liners, shorter than AV691/760, so a price was struck and we were in the process of concluding a deal when Searle’s pulled an old liner out of my block…

…and it blew apart the myth that they were thicker - they were in fact exactly the same thickness as AV800/801 liners. In fact, after an awful lot of checking and measuring, it was actually established that the AV740 liners are EXACTLY the same dimentionally as AV691 liners, with the exception of their length, obviously due to the V8’s much shorter stroke. A set of eight new semi finished AV691 liners were found and bought in the UK, sent to a speciallist machine shop who mounted them on a purpose made solid nylon mandrel to machine down their length to exactly match the V8 AV740 liners. With this work done, the new liners were pressed into the block using a specially made depth gauge (to set the correct liner protrusion), bored and honed to the new AEC issued tollerance of 130.00mm…

…the completed block was then sent back upto Steve Mayle for assembly. For those who don’t know Steve, he and his son Johnny restored the well known Mandator V8 LVL164H to a very high standard back in 2000. He is a veteran of AEC engines, an exceptionally experienced and skilled fitter from the old school, a font of knowledge, and quite simply the best person in the UK to undertake this work…

In the next part we will look at the cylinder heads.
To be continued…

[ramone]

ERF:
Now seems a relatively good point to start the restoration story of the AVM8-740 engine in the video above.

Part One.

This is engine number 316, a relatively late build from very late in 1969. It is the original engine as fitted to my Mandator V8 chassis when it was built, and was alternated and rebuilt together with a prototype V8 engine at major overhaul intervals by the original operator to keep the vehicle on the road. This system lasted until it hauled it’s very last load in 1977, at which point the prototype unit was installed and engine 316 had ‘alledgedly’ been rebuilt ready to fit and then stored - this turned out to be far from the case.

This is engine 316 exactly as it was removed from it’s dry storage by me back in 1991 (although this is a 2015 photo)…

6

The stripdown began in May 2015…

5

…and revealed many horrors, including lots of evedence of various pistons ‘picking up’ on the liners due to overheating, and the liner cracking issue described above…

4

All the bare castings were then sent over to SPL at Dudley to be completely stripped clean of any rust and paint. This is a very sophisticated chemical process that removes all contamination, inside and out, but crucially does not remove any sound metal. The process is used by Catapillar and the MoD amongst others in the course of reconditioning their large engines. The photo here is on arrival at SPL…

3

The cleaned block and heads were then sent over to Ivor Searle Ltd., a long established engine reconditioning machine shop based in Soham. We knew the liners were all scrap, but with no replacements available anywhere it looked like we had hit our first major hurdle. Working on the widely accepted information (wrongly) that the AV740 liners were thicker walled than AV800/801 items, we searched the world for suitable liners, and found a supplier in Australia with ten liners in stock that he was sure were for the AV740 AEC V8. The liners he had were thicker than AV800 liners, shorter than AV691/760, so a price was struck and we were in the process of concluding a deal when Searle’s pulled an old liner out of my block…

2

…and it blew apart the myth that they were thicker - they were in fact exactly the same thickness as AV800/801 liners. In fact, after an awful lot of checking and measuring, it was actually established that the AV740 liners are EXACTLY the same dimentionally as AV691 liners, with the exception of their length, obviously due to the V8’s much shorter stroke. A set of eight new semi finished AV691 liners were found and bought in the UK, sent to a speciallist machine shop who mounted them on a purpose made solid nylon mandrel to machine down their length to exactly match the V8 AV740 liners. With this work done, the new liners were pressed into the block using a specially made depth gauge (to set the correct liner protrusion), bored and honed to the new AEC issued tollerance of 130.00mm…

1

…the completed block was then sent back upto Steve Mayle for assembly. For those who don’t know Steve, he and his son Johnny restored the well known Mandator V8 LVL164H to a very high standard back in 2000. He is a veteran of AEC engines, an exceptionally experienced and skilled fitter from the old school, a font of knowledge, and quite simply the best person in the UK to undertake this work…

0

In the next part we will look at the cylinder heads.
To be continued…

I`m hooked already cant wait for the next part

[sir]

^^ +1 Fascinating. Thank you.

[carryfast]

Sir +:
^^ +1 Fascinating. Thank you.

+1

[gingerfold]

Carryfast:
On that note how did the wet liner AEC engines perform in terms of reliability and did they suffer with any of the issues being described in the case of the 691 and 740 at least ?.

AEC had periods in its existence when its engine ranges alternated between wet and dry cylinder designs. The A410 / A470 engine introduced in 1953 was a wet liner engine and its origins were from a 6.6 litre engine of the 1930s. (Not the 7.7 litre engine as often erroneously stated). Early A470 engines had a reputation for head gasket failures, usually between numbers 5 and 6 cylinders. The contemporary larger wet liner engine, A590 / A690 didn’t suffer head gasket failure to anything like the same degree as its smaller cousin. AEC eventually made the A470 engine into a reliable unit after numerous trials with different gasket materials, re-designed cylinder heads, additional cylinder head studs, and finally switching to unified thread studs, the designation becoming AVU470 (vertical engine) and AHU470 (horizontal engine). The A471/505 and A691/760 ranges replaced the previous range in 1965, reverting to dry liners. I think that I’m correct in saying that a dry liner engine is more rigid, or stiffer, than a wet liner engine. The AEC engines described above were also monobloc designs, earlier engines such as the 7.7, 9.6, and 11.3 litres had separate crankcases and cylinder blocks.

[frankydobo]

I would think looking back to when I was an apprentice fitter with an AEC dealership the majority of work we done was head gasket replacement, something I had also become familiar with in my previous and first employment with a haulage company that ran mostly AEC’s and the Ergo 505 engined motors seemed to be what I recall mostly working on, however a head gasket job wasn’t considered a big thing most engines suffered from blown heads then and I quite liked doing them anyway especially on the tilt cabs and I must have got quite good at it as the gaffer had me do the V8 Demo that limped in and then quickly got sent packing South once sorted, he said at the time that engine would be the ruin of AEC but back then not many old time fitters were keen on any V8 diesels saying they weren’t reliable enough. I was dead chuffed to have done that job though and as it happened once I came out of my time I never touched another AEC engine. I can’t recall now the AEC engine types I pulled out Wet or Dry liners but it seemed both types were still in use at the same period. Franky.

[carryfast]

gingerfold:

Carryfast:
On that note how did the wet liner AEC engines perform in terms of reliability and did they suffer with any of the issues being described in the case of the 691 and 740 at least ?.

AEC had periods in its existence when its engine ranges alternated between wet and dry cylinder designs. The A410 / A470 engine introduced in 1953 was a wet liner engine and its origins were from a 6.6 litre engine of the 1930s. (Not the 7.7 litre engine as often erroneously stated). Early A470 engines had a reputation for head gasket failures, usually between numbers 5 and 6 cylinders. The contemporary larger wet liner engine, A590 / A690 didn’t suffer head gasket failure to anything like the same degree as its smaller cousin. AEC eventually made the A470 engine into a reliable unit after numerous trials with different gasket materials, re-designed cylinder heads, additional cylinder head studs, and finally switching to unified thread studs, the designation becoming AVU470 (vertical engine) and AHU470 (horizontal engine). The A471/505 and A691/760 ranges replaced the previous range in 1965, reverting to dry liners. I think that I’m correct in saying that a dry liner engine is more rigid, or stiffer, than a wet liner engine. The AEC engines described above were also monobloc designs, earlier engines such as the 7.7, 9.6, and 11.3 litres had separate crankcases and cylinder blocks.

Thanks for that Gingerfold.Also one of the main disadvantages of wet liner engines is the problem of sealing it against water getting into the crankcase and oil getting into the water jacket.While as we’ve seen the issue of combining dry or wet liners with a decked block is that of dealing with the conflict between the block deck interfering with the head clamping at the top face of the liner obviously creating all sorts of complications in that regard.Which the CAT C15 for example seems to have taken to an extreme in using a ‘spacer plate’ to deal with the issue of the ‘void’ ? beneath the liner flange as described in the case of the 691/740. It will be interesting to find out if that issue at least might have somehow been circumvented during the story of the project as it unfolds.

youtube.com/watch?v=Srq-8qGbQKM

I’d guess that the Jag V12 wet liner type design provides the best of all worlds of very good location and seal of the liner with no need for a decked block and therefore any of the resulting associated issues described.

[erf]

Carryfast:
…one of the main disadvantages of wet liner engines is the problem of sealing it against water getting into the crankcase and oil getting into the water jacket.While as we’ve seen the issue of combining dry or wet liners with a decked block is that of dealing with the conflict between the block deck interfering with the head clamping at the top face of the liner obviously creating all sorts of complications in that regard.Which the CAT C15 for example seems to have taken to an extreme in using a ‘spacer plate’ to deal with the issue of the ‘void’ ? beneath the liner flange as described in the case of the 691/740. It will be interesting to find out if that issue at least might have somehow been circumvented during the story of the project as it unfolds…I’d guess that the Jag V12 wet liner type design provides the best of all worlds of very good location and seal of the liner with no need for a decked block and therefore any of the resulting associated issues described.

Peugeot used a similar method to the Jag V12 wet liner location in their small Diesel engine, but as engine size increases, so does physical stress on the engine, and that design cannot provide the rigidity required of high torque outputs in commercial applications - although I know it has been experimented with, and failed due to block flex.

Shimming of liners under the top flange is not an unusual thing at all with large commercial engines using wet liners, and many manufacturers including Volvo and in some applications ■■■■■■■ require their liners to be fitted into the block without seals, measured for block face protrusion, shims selected then the liner finally fitted with the shim and seals.

Shimming of flanged type dry liners, which have a much narrower flange, is virtually unheard of. The usual practice being to fit them fully home into a counterbore provided in the block face - as per the AEC AV760/800/801 engines. The 691/740 are very unusual in their requirement, and during the course of this restoration I have conversed with some really interesting and knowledgable professional people involved with Diesel engine design. A former Perkins design engineer really could not fathom what AEC were thinking here, but it’s not an easy thing to change or do anything about. To select a shim (assuming we could have them made - they wound be tiny in physical size as the flange is only a couple of mm larger in diameter than the liner - see the sectioned V8 photo on the previous page) would require the liner fitting to the block to be measured, then removing to fit the selected shim - bearing in mind this requires about thirty tons of force, not a practical proposition with the rare and fragile centrifugally cast (cast iron) liners that we were working with. So the AEC original design prevailed, but the new liners were very accurately fitted into the block, and as a precaution were secured in place with a special heat conducting loctite, which gives the best possible prospect for this rather compromised design.

[gingerfold]

Fascinating and very interesting. Bearing in mind that we’re discussing engine design(s) dating back over 50 years, to the early - mid’ 1960s then the application of advances in design and technology that have occurred in the intervening years that can be used in this V8 should make it reliable.

I think that it is also worth mentioning that AEC, as with most major engine manufacturers, had design and development in its in-line engine ranges that progressed from early designs to later designs with improvements that reflected technological and metallurgical advances, and also gleaned knowledge from other makers. All vehicle builders dismantled and analysed competitors’ engines and components. The V8 project was a clean sheet design and AEC, or Leyland for that matter, had never designed or built anything like it. It is interesting that ERF has also found some commonality in design and even components with contemporary AEC in-line engines, nothing wrong with that in the broader scheme of things, but it does beg the question, was the V8 subject to budget constraints even in the early 1960s? Bob Fryars is on record as saying that his team at AEC always regarded the V8 project as nothing more than a concept programme to begin with and they were horrified when they were told by Leyland that it had to be ready for mainstream production by early 1968. They knew that the design was unproven. I also wonder if Ricardo had any input into design and development of the V8, as AEC had used them for earlier engines.

[windrush]

Going slightly ‘off topic’ but the BMC wet liner engines in the FJ suffered badly with liner drop (even during manufacture) resulting in scrapped blocks, however the later 4/98 and 6/98 engines in the Terrier and Boxer ranges used a different sealing method at the bottom of the liner and also the replacement liners were supplied several thou overheight and required grinding in on rebuild with valve grinding paste to get the neccessary standproud which solved most of the problems.

Pete.

[erf]

gingerfold:
… Bearing in mind that we’re discussing engine design(s) dating back over 50 years, to the early - mid’ 1960s then the application of advances in design and technology that have occurred in the intervening years that can be used in this V8 should make it reliable.

There will be more on this subject later in the story. Even advances stemming from motorsport found an application in this V8 rebuild.

gingerfold:
I think that it is also worth mentioning that AEC, as with most major engine manufacturers, had design and development in its in-line engine ranges that progressed from early designs to later designs with improvements that reflected technological and metallurgical advances, and also gleaned knowledge from other makers. All vehicle builders dismantled and analysed competitors’ engines and components. The V8 project was a clean sheet design and AEC, or Leyland for that matter, had never designed or built anything like it. It is interesting that ERF has also found some commonality in design and even components with contemporary AEC in-line engines, nothing wrong with that in the broader scheme of things, but it does beg the question, was the V8 subject to budget constraints even in the early 1960s? Bob Fryars is on record as saying that his team at AEC always regarded the V8 project as nothing more than a concept programme to begin with and they were horrified when they were told by Leyland that it had to be ready for mainstream production by early 1968. They knew that the design was unproven. I also wonder if Ricardo had any input into design and development of the V8, as AEC had used them for earlier engines.

Some of the very talented people I have been lucky enough to receive advice and input from, and who are/were both modern day engine designers and specialists in modern engine machining, knew of the AEC V8. Some knew quite a lot about the design (Perkins for instance) and were quite open that very valuable lessons had been learnt from it (coolant circulation in a Vee engine being a case-in-point), others knew next to nothing but were very interested. All of them, every single one, respected the professional bravery of the design team working on the project 50+ years ago. They were working in what would be impossible circumstances today. Trying to create a brand new engine design with nothing tangible to follow but their own manual theoretical calculations arrived at from straight-six experience, and hand drawings. As if that were not enough, they had the parent Leyland organisation effectively working against them at every turn. It is amazing, it really is, that they ever got even a running V8 engine off the drawing board and into a lorry, so despite the ultimate outcome, we must reflect on that.

[carryfast]

ERF:
Peugeot used a similar method to the Jag V12 wet liner location in their small Diesel engine, but as engine size increases, so does physical stress on the engine, and that design cannot provide the rigidity required of high torque outputs in commercial applications - although I know it has been experimented with, and failed due to block flex.

Shimming of liners under the top flange is not an unusual thing at all with large commercial engines using wet liners, and many manufacturers including Volvo and in some applications ■■■■■■■ require their liners to be fitted into the block without seals, measured for block face protrusion, shims selected then the liner finally fitted with the shim and seals.

Shimming of flanged type dry liners, which have a much narrower flange, is virtually unheard of. The usual practice being to fit them fully home into a counterbore provided in the block face - as per the AEC AV760/800/801 engines. The 691/740 are very unusual in their requirement, and during the course of this restoration I have conversed with some really interesting and knowledgable professional people involved with Diesel engine design. A former Perkins design engineer really could not fathom what AEC were thinking here, but it’s not an easy thing to change or do anything about. To select a shim (assuming we could have them made - they wound be tiny in physical size as the flange is only a couple of mm larger in diameter than the liner - see the sectioned V8 photo on the previous page) would require the liner fitting to the block to be measured, then removing to fit the selected shim - bearing in mind this requires about thirty tons of force, not a practical proposition with the rare and fragile centrifugally cast (cast iron) liners that we were working with. So the AEC original design prevailed, but the new liners were very accurately fitted into the block, and as a precaution were secured in place with a special heat conducting loctite, which gives the best possible prospect for this rather compromised design.

I should have included my other favourite option which as expected seems to go along the lines of keep it simple but effective.

youtube.com/watch?v=YXSPmUcUGHc

[8lxbv8brian]

Frankydobo:
I would think looking back to when I was an apprentice fitter with an AEC dealership the majority of work we done was head gasket replacement, something I had also become familiar with in my previous and first employment with a haulage company that ran mostly AEC’s and the Ergo 505 engined motors seemed to be what I recall mostly working on, however a head gasket job wasn’t considered a big thing most engines suffered from blown heads then and I quite liked doing them anyway especially on the tilt cabs and I must have got quite good at it as the gaffer had me do the V8 Demo that limped in and then quickly got sent packing South once sorted, he said at the time that engine would be the ruin of AEC but back then not many old time fitters were keen on any V8 diesels saying they weren’t reliable enough. I was dead chuffed to have done that job though and as it happened once I came out of my time I never touched another AEC engine. I can’t recall now the AEC engine types I pulled out Wet or Dry liners but it seemed both types were still in use at the same period. Franky.

This must have been Lex on Benton road? I remember this not 100% sure but I think it was down to come to Waughs as a demo some time at the time came down to see it
in the workshop with Mr Scott(Ralllpppphhhhhyyyyyy-Kevmac will get this :lol ) who just lived up the road from lex-tilletsons on Benton road it was quite the talking point
in the workshop(waughs) at the time the one engine with 8-cylinders one after other in a line won -

[frankydobo]

That’s right Brian it was still Hodgson’s when I started there but had the name change about a year later although it was known about before that and we got a Manager from down South to go with it, he was an ok bloke and didn’t interfere as far as the workshop was concerned. By the way in my previous job at Ellis transport Ian Forrest, who later went to Waugh’s, was one of the fitters I learnt a lot from especially with the AEC’s. Franky.

[chris_webb]

Chris Webb:
Just going off the V8 subject,I once got a lift over Woodhead in a Mandator of W H Martins from Brigg,loaded with billets out of Scunthorpe.It had a Fuller box,not sure if it was the 9-speed RTO9509 that was in the Marathon.The thing about it was that it improved the AV760 engine performance no end and I was suitably impressed.I wonder how many AV760 Mandators were fitted as such? I had a Mandator at the time,OKC 130M and wanted a Fuller in it asap.
I wonder what the comparison would have been like between a V8 Mandator with a 6-speed box and the AV760 Mandator with a Fuller performancewise?

Bumped this up…

[erf]

Chris Webb:

Chris Webb:
Just going off the V8 subject,I once got a lift over Woodhead in a Mandator of W H Martins from Brigg,loaded with billets out of Scunthorpe.It had a Fuller box,not sure if it was the 9-speed RTO9509 that was in the Marathon.The thing about it was that it improved the AV760 engine performance no end and I was suitably impressed.I wonder how many AV760 Mandators were fitted as such? I had a Mandator at the time,OKC 130M and wanted a Fuller in it asap.
I wonder what the comparison would have been like between a V8 Mandator with a 6-speed box and the AV760 Mandator with a Fuller performancewise?

Bumped this up…

The Fuller gearbox in the Mandator you had a ride in would have been an RTO-610 or an RTO-609 Chris, depending on the year. The AV760 powered 2TG4R Mandators were offered with a Fuller gearbox as an option, but very few were sold compared to those equipped with the standard T.E.T. 6 speed.

The RTO-610/609 is a physically smaller gearbox than the RTO-9509, and strictly speaking was operating right on its recommended torque limit, or slightly over it when coupled to an AV760 engine equipped with a Bosch injection pump, but fitting the larger gearbox in a standard home market Mandator tractor unit was impossible as there physically wasn’t enough room lengthwise.

Officially the V8 Mandator was never offered with a Fuller option, but was offered with a rather crude in comparison T.E.T. 10 speed splitter. Export territories, Leyland Australia and New Zealand in particular, did offer a Fuller RTO-910 or 915 option, they were able to offer the larger gearbox because the export chassis was both deeper and could be built up with a longer wheelbase. The chassis rails supplied in the CKD kits were long enough to accommodate various operators wheelbase requirements. At least three of the restored V8 Mandator’s have been retro fitted with Fuller RTO-609 gearboxes, and it is said to much improve the drive, being well suited to the V8 engine’s torque band, but behind the V8 engine it is operating over it’s torque limit - not much of a problem in preservation of course.

[gingerfold]

What gearbox is in your Mandator V8…or what gearbox will it have when finished?

[erf]

gingerfold:
What gearbox is in your Mandator V8…or what gearbox will it have when finished?

My ultimate aim throughout the project has been to restore my V8 to as close to the specification it left Southall as possible, so that it’s an accurate representation in a technicial sense if anyone was interested enough to study the model in the future, but make improvements where modern processes and materials can be incorporated without compromising originality.

To this end, I’m sure my V8 will be one of the few remaining that still feature things like the original factory fuel pipe routing - most if not all were changed in service to a much simpler layout with the filter bowls mounted higher to try to reduce poor starting problems caused by fuel running back. Mine suffered from it, and was modified, but it’s all been restored back to the original design.

I did consider fitting a Fuller gearbox in the early days, but as it was never a UK option for the V8, I have stuck with the D250 six-speed…but there lies another story in the gearbox.

As you know, the five and six speed gearboxes (and the ten-speed splitter) fitted to AEC’s were supplied by T.E.T. (Transport Equipment Thornycroft). The D250 gearbox differs from the standard gearbox found in the six-cylinder Mandator etc, the D203, because the input (or spigot) shaft through the clutch is 2.00" in diameter as opposed to 1.750" in the D203, and also the gear change housing on the top is extended out to reach past the right hand bank of the Vee to the gear-lever. My original D250 gearbox was scrap, it had alllowed rain water in through the top which had reached a depth sufficient to freeze and spilt the casing lengthwise along the bottom. The very early six-speed V8’s were fitted with a D236 gearbox, this was a D203 complete with 1.750" shaft, but with the extended top housing. These gearboxes gave problems in service behind the V8 engine, so at some point in early to mid 1969, the D250 was developed to beef up the unit. When I came to search for a replacement gearbox I drew a complete blank. I found D203’s and even a D236’s, but all the D250’s I found were just as bad as my original - they really don’t like to stand idle outside for years. The V8 was the only AEC fitted with a 2.00" shaft gearbox (not even the Millitant version had it), but eventually I found out that Scammell had specified it in a T.E.T. gearbox later in the 1970’s for the Routeman etc. Luckily I was steered towards a guy that ran Scammell’s years ago, but still had lots of gearbox parts, so he was able to build me up a gearbox using my V8 bellhousing and top housing, but incorporating the design improvements that T.E.T. (by then part of Eaton) had made through the 1970’s to make the gearbox into a heavy-duty version (the D26? I think) including needle roller bearings on the mainshaft, as opposed to the original D250’s bronze bushes.

[gingerfold]

This might be a silly question, but do you have a target date for completion of the project as I’m certain it will be well worth seeing when completed.

[erf]

gingerfold:
This might be a silly question, but do you have a target date for completion of the project as I’m certain it will be well worth seeing when completed.

Well that’s kind of you to say Graham, it will certainly look very different from when you last saw it, but no, I don’t have a target date. I have owned it for 26 years now, but we only really got stuck into it back in 2013. It’s very very close to completion to be honest, but just when you seem to be making good progress it tends to bite back with a difficult problem - as only AEC V8’s can - so I’m crossing my fingers…