AEC V8

[ramone]

ERF:
AEC V8 Engine Restoration - Part Two.

(Part one is several pages back now, if anyone lands here and is looking for it).

In this part we will cover the cylinder heads.

The original heads from engine 316 were chemically cleaned inside and out at the same time as the block, and were sent over to Ivor Searle of Soham for reconditioning and hot pressure testing. Hot pressure testing involves sealing off all the water ports, immersing the head into a tank of hot water at normal engine running temperature, and applying air pressure to the water channels in the head so that any leaks can be seen as bubbles. After a couple of weeks I got the call I’d been dreading - your heads are both cracked.

I went over to Soham to see for myself and plan the way forward, but the news was not good. One head had failed the hot pressure test catastrophically, with bubbles coming from deep within an exhaust port - probably due to the ‘hot spot’ cracking mentioned earlier in the thread, where the coolant boils within the head, forms a steam pocket allowing the iron to dramatically heat up, then gets cooled suddenly when the coolant begins to flow again as the RPM of the water pump increases. This particular head was scrap, no feasible repair could be done with the crack being located so deep in the port. The other head had failed it’s hot pressure test too, this time leaking around two of the injector sleeves, but with a set of dummy injectors fitted and torqued down, it was re-tested and passed with no leaks.

At this time the second head was due to be refaced by Searles, and was showing clear cracks between the injector hole and the valve seats. As those with experience of direct injection Diesel engines will know, this type of cracking is very very common, and although never ideal it is often not a cause of great concern if it is considered minor. As these cracks were not leaking under pressure when hot, it was all of our thinking that they would not be an issue - but I was far from happy to leave it as I was striving to create as close to a new engine as possible…

3

The search was now on for pair of replacement heads, no easy task with an engine as rare as an AEC V8. They had to be AV740 heads too, as the AV800 heads have bigger valves to suit the larger bore size that will not clear the top edge of the AV740 liners. A lucky break (or so it seemed) came in the form of a pair of heads from a former AEC V8 owner who had acquired what he believed to be a pair of brand new unused AV740 heads as spares for his engine. These were bought and stripped down, during which it became very obvious that they had been at least run on an engine due to the presence of carbon in the ports. These heads were sent off for chemical cleaning, as before…

2

It was then back to Soham for another round of hot pressure testing with everything crossable crossed!. But to no avail - I got another phone call to say that one of the replacement pair of heads had a catastrophic crack into one of the oil galleries. This really was a double blow, the heads had been bought as new items, but clearly were not, and on top of that one was cracked!. I got a real sense at this point that patience was wearing very thin at Searles with me and my seemingly endless stream of unserviceable engine parts, so I collected everything up and took time to collect thoughts on a way forward.

I now had four heads, and with them all on the bench one day noticed something quite interesting. The original heads from engine 316 were marked with a cast ‘A’ between the centre valve guides, one of the replacements was similarly marked, but the other was marked ‘A1’. On studying them all, the ‘A1’ head had some obvious modifications to the casting compared to the other three, and it was this head which had passed the last hot pressure test. At this point in the project I was really lucky to find a guy called Simon Smart who runs Automotive Services in Northampton, a firm specialising in reconditioning all types of engine components. I should perhaps point out that the Northampton area is great for finding really good engine machine shops and the like because of it’s proximity to Silverstone and the motorsport businesses based there - something which would benefit this AEC V8 project more than once over it’s course.

Simon took a genuine interest in the V8, not least because he knew AEC’s from his fathers time as a lorry driver for London Brick in the 60’s and 70’s. Simon re-tested all four heads, and reached the same conclusion as Searles, the ‘A1’ head had passed the hot pressure test with no issues at all, and one of the original ‘A’ heads had passed, but had the minor face cracking. The search was now on again to try to find yet another head to make a perfect pair for engine 316. A worldwide search proved fruitless, but eventually a complete engine was located which had allegedly been rebuilt by AEC at some point in it’s life. This engine was bought, stripped and noted to have one head marked ‘A1’, and another head marked ‘A2’ - with even further casting modifications!..

1

0

Now the thing we must recognise here is that engine 316 was built very late in 1969, and was one of the last AV740 engines built before sales of the AEC Mandator V8 were suspended. The fact that improved ‘A1’ and ‘A2’ marked heads were produced after the ‘A’ marked heads originally fitted to engine 316 proves that AEC were still working to get some of the V8’s reliability issues addressed even after production had stopped, something I don’t think has ever been credited to them.

The most recently acquired pair of heads were again chemically cleaned and then sent off to Simon, and this time both passed the hot pressure test, and both had no face cracking - so after six cylinder heads at last we had a perfect pair, and even a spare!. Simon selected the very best pair dimensionally and set about fully reconditioning them with a face re-grind, re-cut valve seats, brand new old stock valves and new metric valve guides which he actually managed to cross reference from a Rolls Royce application.

The heads were now fully sorted and ready to go, so it was time to look at the crankshaft, pistons and camshaft - in the next instalment!.

Thanks again for posting another excellent chapter i cant wait for the next 1

[cav551]

I had forgotten that my old firm had run two V8 Mandators CGF 420H and OKK 160F. They, like the Maggie Deutz units, known by Henleys as ‘Humbolts’, had gone before I started.

[ramone]

Were the higher powered V8s the better option reliability wise or did I dream that 1?

[zb_anorak]

ramone:
Were the higher powered V8s the better option reliability wise or did I dream that 1?

The 800 was easier to cool, due to thinner liners, IIRC.

[zb_anorak]

Carryfast:
If all other options run out it is possible to obtain new custom made castings from specialists.

Good idea, but it might be cheaper to buy a new lorry .

If someone can get hold of a full set of the casting drawings, a good foundryman could generate a set of pattern drawings, then we could all make bits of it. I bet there are numerous contributors to these threads who can read a drawing and work with wood. Without disrespecting patternmakers one jot, I reckon those people who build model lorries would ■■■■ a set of casting patterns.

[carryfast]

ramone:
Were the higher powered V8s the better option reliability wise or did I dream that 1?

The bigger bore of the 801 might have allowed for wider rods and ends ?.Although the Scania 140 seemed to work ok with a 127 mm bore.IE more proof of the diminishing returns in concentrating on piston speeds at the expense of leverage.

I’d guess that going for modular 590 based 120 x 142 for medium duty spec and 690 based 130 x 142 for heavy duty would have been a good solution.Providing at least around 200 + hp and 270 hp potential respectively in NA form based on just the 590’s and 690’s figures.Let alone the 690 T’s.

[carryfast]

[zb]
anorak:

Carryfast:
If all other options run out it is possible to obtain new custom made castings from specialists.

Good idea, but it might be cheaper to buy a new lorry .

If someone can get hold of a full set of the casting drawings, a good foundryman could generate a set of pattern drawings, then we could all make bits of it. I bet there are numerous contributors to these threads who can read a drawing and work with wood. Without disrespecting patternmakers one jot, I reckon those people who build model lorries would ■■■■ a set of casting patterns.

3dealise.com/du/3d-druck.html

[erf]

[zb]
anorak:

ramone:
Were the higher powered V8s the better option reliability wise or did I dream that 1?

The 800 was easier to cool, due to thinner liners, IIRC.

2.5mm thinner parent bore (cylinder wall) in the block casting - the actual liners are exactly the same thickness, but you are correct that they transferred heat more effectively than the AV740, and were better in that respect. In all other areas they all suffered from the same problems.

[zb]
anorak:

Carryfast:
If all other options run out it is possible to obtain new custom made castings from specialists.

Good idea, but it might be cheaper to buy a new lorry .

If someone can get hold of a full set of the casting drawings, a good foundryman could generate a set of pattern drawings, then we could all make bits of it. I bet there are numerous contributors to these threads who can read a drawing and work with wood. Without disrespecting patternmakers one jot, I reckon those people who build model lorries would ■■■■ a set of casting patterns.

You are absolutely correct - it would be cheaper to buy a new lorry!.
It is entirely possible to have new patterns made for any component, but the costs are eye-watering for complicated hollow castings like cylinder heads. Then there is the machining. We are quite lucky to have a company called South Lincs Foundry near here who are also pattern makers, and they have made several small items for the V8. They are capable of anything though, making new cylinders for a full size mainline steam locomotive when I was last there!.

Carryfast:
The bigger bore of the 801 might have allowed for wider rods and ends ?..

No, because the AV740 and AV800/801 used the same block casting and crankshaft.
These were items that AEC could not improve substantially during and after production (in the way they did with the cylinder heads) because it would have involved a series of minor changes that required a full redesign of the engine castings and tooling, something they had no budget for because there was no appetite for it within Leyland, as in their eyes the V8’s reputation was already ruined - which was a fair point, but as I hope to show in the coming installments of the restoration, the outcome for the AEC V8 engine could have been such a different story.

gingerfold:
Fascinating and very detailed. What time scale is involved here? From taking the first heads to Ivor Searle to finally getting your “as new” heads?

There are several verified accounts that AEC continued to work on the V8 engine after sales were suspended. I do have an official AEC / Leyland policy document that states that an improved V8 was being considered for re-launch in 1971.

The time scale with the heads was about five months all in. It was a lot of effort and expense.

I am absolutely 100% confident that had the improved engine been re-launched in 1971 it would have been a resounding success. It was SO very nearly right in many many ways, and had the information from the prototypes been assessed properly and design modifications made before production commenced, the story would be very different. I can only begin to imagine the frustration and disbelief of the AEC design team in 1967/68.

gingerfold:
Just another thought. AEC never had its own foundry, so which foundry was AEC working with in re-designing these castings? Historically AEC’s casting suppliers were Ley’s and Qualcast, but by the time of the V8 were castings being supplied from Leyland’s own foundry?

All the V8 castings that I have seen are Ley’s marked. I have never seen a V8 casting marked with the Leyland Foundry ‘plughole’ logo.

[gingerfold]

I don’t suppose that Ley’s are still in existence?

[zb_anorak]

gingerfold:
I don’t suppose that Ley’s are still in existence?

According to Wikipedia, the foundry was demolished in 1986:
en.wikipedia.org/wiki/Francis_Ley

[gingerfold]

[zb]
anorak:

gingerfold:
I don’t suppose that Ley’s are still in existence?

According to Wikipedia, the foundry was demolished in 1986:
en.wikipedia.org/wiki/Francis_Ley

I’d always wondered why Derby County’s old football ground was named “The Baseball Ground”, now I know. Trucknet does answer some obscure questions.

[carryfast]

ERF:

Carryfast:
The bigger bore of the 801 might have allowed for wider rods and ends ?..

No, because the AV740 and AV800/801 used the same block casting and crankshaft.
These were items that AEC could not improve substantially during and after production (in the way they did with the cylinder heads) because it would have involved a series of minor changes that required a full redesign of the engine castings and tooling, something they had no budget for because there was no appetite for it within Leyland, as in their eyes the V8’s reputation was already ruined - which was a fair point, but as I hope to show in the coming installments of the restoration, the outcome for the AEC V8 engine could have been such a different story.

I am absolutely 100% confident that had the improved engine been re-launched in 1971 it would have been a resounding success. It was SO very nearly right in many many ways, and had the information from the prototypes been assessed properly and design modifications made before production commenced, the story would be very different. I can only begin to imagine the frustration and disbelief of the AEC design team in 1967/68.

Firstly there seem to be references to rods/ends failures ?.Not sure if that means both the 740 and the 801 ?.Logically beefing the assembly up by extending the width of the rod and the rod end if at all possible would be one of the expected fixes ?.Especially in this case of an increase in bore diameter allowing the piston/rod/crank pin/journal to be extended accordingly ?.

Instead of which at best they knew that they were already on,if not over,the margins regarding the force v leverage equation.Then they add even more force to the rod by increasing the bore size but without beefing up the assembly accordingly ?.Or at worse they already knew they were getting bottom end failures with the 130 bore ?.Then they increased it to 135 using the same rod/end width/journal length measurements as before ?.

Assuming all the original measurements had to remain as before it’s difficult to see how they could have beefed up the design to the point where they could have signed it off as a success.On that note it’s obviously impossible to make any conclusive suggestions in that regard without subjecting a potentially ‘improved’ design to the same dyno loadings and durability testing as the factory would have done to meet its design loads and which obviously condemned it to the point of removing it from availability.

There’s hopefully no way that you’d possibly do that to this piece of automotive history and like the original it’s best chance is to make sure that it’s not loaded to anything like the type of duty regime that it was originally envisaged to meet by its muddle headed designers.

IE make no mistake this was always going to be best suited to no more than a 6 wheeler from day 1 and obviously nothing more than an empty artic now in preservation and retirement.

[gingerfold]

Carryfast, why don’t you let ERF give us his experience, conclusions, and opinions before spouting your own “muddle headed” opinions. ERF is someone who is actually spending countless hours and a very substantial amount of money in restoring an engine. He deserves our respect and admiration. All you do is denigrate AEC, its designers, purchasers of the vehicles, drivers and those of us who do know something about the heritage, history, and products of one of the country’s most important commercial vehicle manufacturers that DID contribute much to commercial vehicle design and development. All you do is write the same fatuous, puerile, inane, and ill-informed comments time and time again. You wouldn’t know an AEC V8 engine if one fell out of the sky and hit you on the head. Might be a good thing if one did, might knock a bit of sense into you. Rant over for now.

[erf]

Carryfast:
Firstly there seem to be references to rods/ends failures ?.Not sure if that means both the 740 and the 801 ?.Logically beefing the assembly up by extending the width of the rod and the rod end if at all possible would be one of the expected fixes ?.Especially in this case of an increase in bore diameter allowing the piston/rod/crank pin/journal to be extended accordingly ?.

…it’s best chance is to make sure that it’s not loaded to anything like the type of duty regime that it was originally envisaged to meet by its muddle headed designers.

IE make no mistake this was always going to be best suited to no more than a 6 wheeler from day 1 and obviously nothing more than an empty artic now in preservation and retirement.

Where do I start…?!
Against my better judgement, I will try to help you see things differently (again).

Connecting rod failures must have been very rare in this engine, because in all my years of association, I have not heard of a single one. Big end bearing shell failures, yes, but except in the worse cases the engine would get you home, not break the rod and put it through the block, if that is what you are saying?.

The AEC V8 designers were trying to create a engine with everything, high power, low weight, good torque, compact proportions…all from a clean sheet. They created four prototype running engines and fitted them into goods vehicle chassis for testing and evaluation. As any engine designer will tell you, a prototype engine is not built to production standards and design. Service life is part of the design that is addressed after initial prototyping, the first engines are built purely to assess data to see if the basics are right before any required changes are made and expensive production line tooling is bought and set up. This is where it went wrong for the AEC V8. The design engineers had good solid data from their test engines in all operating climates. They knew the big end journals were too narrow. They knew they had to completely re-think the coolant circulation path. They knew many other small detail changes had to be made to take the engine from a prototype to a full production reliable engine. This did not happen. The only changes made between prototype and production were minor, and I will list them. The block core was changed (presumably at Ley’s request) to incorporate long side openings to the outer water jackets. This was purely for reasons of casting, nothing to do with the base design. The fixing threads were all changed from BSF and UNF to Metric, purely to standardise with other engine production. The head castings were changed to the ‘A’ marked type which accommodated a single long rocker cover on each head, rather than the twin covers on each head as featured on the prototypes.
That is it.
In all other respects AEC were forced to start production of a prototype engine, and I say agan, I can only imagine the frustration of the design team, who everyone except yourself credits with a very innovative and clever design. Even seasoned professional engine designers with all the benifits of modern CAD systems at their disposal at world leading Diesel engine manufacturers acknowledge this.

My own Mandator V8 operated dual shifted from 1970 to 1977. It was a single V8 in a sizable fleet of AV760 powered Mandator’s. They were a firm known around here for working their lorries hard, mostly on brick transportation. It was (and still is) rare to see their lorries going up the road anything other than fully freighted. In the early 1970’s they were a firm operating with stiff competition and with relatively modest margins. Despite all this, in 1971 when AEC wanted to take their V8 away and sell them a new AV760 powered replacement Mandator at cost, they refused. Every one of their drivers to a man wanted to drive the V8 because of it’s performance. Even later in it’s life it was seen as a lorry to ‘graduate’ upto by drivers, even over their brand new Marathon’s. It could haul a full load from A to B as efficiently (if not more so) than an AV760 powered Mandator - BUT at a maintenance penalty. They found the most efficient way to run it was to set realistic milages that the engine could cover without major issues, and when this mileage was reached, to swap the engine with another (prototype as it happened) V8 engine that had been fully overhauled ready to fit. Using this system, and with mechanically sympathetic drivers, the lorry managed seven years of hard work - a completely acceptable life span on their work in the 1970’s. When it was finally withdrawn in 1977 it was so highly regarded by all involved that they refused to scrap it off with all the other worn out lorries, and retained it for purely sentimental reasons - the only lorry they ever kept!.

As all (and I do mean ALL) those lucky enough to drive a Mandator V8 in anger have told me, it was so very right in so many ways. If the AEC engineers had been listened to, and the design changes made that they wanted to make before production, the outcome of this story would have been very very different. I have absolutely no doubt about that.

[newmercman]

ERF you are banging your head against a wall as far as CF is concerned, however, that doesn’t apply to the rest of us, I know you’ve got a lot on your plate with the restoration, but I ask that you post more updates on the project, along with the anecdotes your knowledge of the V8 brings. A few photos would be nice too.

Sent from my SM-T805W using Tapatalk

[ramone]

newmercman:
ERF you are banging your head against a wall as far as CF is concerned, however, that doesn’t apply to the rest of us, I know you’ve got a lot on your plate with the restoration, but I ask that you post more updates on the project, along with the anecdotes your knowledge of the V8 brings. A few photos would be nice too.

Sent from my SM-T805W using Tapatalk

I second that and have hundreds of questions for you but i will leave you to your restoration and the next chapter of this fascinating work you are doing

Thanks

[erf]

ramone:
I…have hundreds of questions for you but i will leave you to your restoration and the next chapter of this fascinating work you are doing…

Thanks, I will write it up when I can, it’s just difficult to find the time to sit and do it!.

The restoration of the lorry is now 95% complete, Steve Mayle has worked very hard on the engine and chassis which are now both fully restored and reunited, and I have finished restoring the cab etc, so it’s mainly a case of detail work before the cab goes on, but this is a V8, and it throws up the most obscure and time consuming problems out of the blue!.

[zb_anorak]

ERF:
…The design engineers had good solid data from their test engines in all operating climates. They knew the big end journals were too narrow. They knew they had to completely re-think the coolant circulation path. They knew many other small detail changes had to be made to take the engine from a prototype to a full production reliable engine. This did not happen. The only changes made between prototype and production were minor, and I will list them. The block core was changed (presumably at Ley’s request) to incorporate long side openings to the outer water jackets. This was purely for reasons of casting, nothing to do with the base design. The fixing threads were all changed from BSF and UNF to Metric, purely to standardise with other engine production. The head castings were changed to the ‘A’ marked type which accommodated a single long rocker cover on each head, rather than the twin covers on each head as featured on the prototypes.
That is it.
In all other respects AEC were forced to start production of a prototype engine, and I say agan, I can only imagine the frustration of the design team, who everyone except yourself credits with a very innovative and clever design. Even seasoned professional engine designers with all the benifits of modern CAD systems at their disposal at world leading Diesel engine manufacturers acknowledge this.

…

Good grief. As far as I can remember from the earlier years(!) of this thread, the project was shelved at an early stage, then rushed to production in very short order, after a hiatus. I did not know the astonishing, almost unbelievable detail that you describe: they knew the engine needed at least one more iteration of development, before any decision on manufacturing could be made, yet the thing was forced into production. Even against the backdrop of progress and risk-taking that characterised the 1960s, the board of directors of Leyland were guilty of unprecedented stupidity. Was it Donald Stokes at the helm? If I remember correctly, he was already a self-glorying maverick, even before he became the big boss. His presence is the detail that makes it all believable.

I loved the story of your own Mandator’s happy life of work. It would be great if we could find out if the raft of engine modifications planned for 1971 were effective. Maybe your rebuild, using the later heads, will give us a clue? Will you be experimenting with the harder journal materials?

[gingerfold]

I will also add that I looked at this particular Mandator V8 about 30 years ago and the cab alone was in a poor state. Even then it was a restoration that was far beyond my own capabilities and resources, causing me to walk away from it. I know who ERF is and his, and his family’s engineering background, manufacturing a very well known and highly regarded product bought and used by hundreds of hauliers over many years. ERF most definitely knows his stuff, and what he says and writes will be 100% correct.

[erf]

[zb]
anorak:
Good grief. As far as I can remember from the earlier years(!) of this thread, the project was shelved at an early stage, then rushed to production in very short order, after a hiatus. I did not know the astonishing, almost unbelievable detail that you describe: they knew the engine needed at least one more iteration of development, before any decision on manufacturing could be made, yet the thing was forced into production. Even against the backdrop of progress and risk-taking that characterised the 1960s, the board of directors of Leyland were guilty of unprecedented stupidity. Was it Donald Stokes at the helm? If I remember correctly, he was already a self-glorying maverick, even before he became the big boss. His presence is the detail that makes it all believable.

Gingerfold has researched and knows more than anyone about the dynamics of the Leyland decision making process at this time.
I will leave him to answer that point, but from a pure engineering point of view, AEC went to production with a prototype engine. That is a fact that we proved more than once during the engine restoration.

[zb]
anorak:
I loved the story of your own Mandator’s happy life of work. It would be great if we could find out if the raft of engine modifications planned for 1971 were effective. Maybe your rebuild, using the later heads, will give us a clue? Will you be experimenting with the harder journal materials?

I am absolutely sure they would have been.
To my knowledge nobody has detailed the changes made for the proposed 1971 engine, but by that time some of the issues had been resolved. The ‘SC’ bearing material developed by Glacier to run on the Tuftrided journals in the wake of big end failures with ‘SB’ material during the TL12 engine development was applied in service to the V8, and with a change in oil specification, acceptable bearing service life was achieved - even with the narrow journals. Today that situation would be even better, because modern synthetic based lubricating oils far out-perform the old mineral oils available in the 1970’s.

The heads we have already covered, the coolant circulation issues - I would be very interested to learn what they proposed for 1971. My guess is that they relocated the water pump and made significant changes to the passages in the block casting, like they did in the heads, but that’s only a guess. There were however some other equally important issues to be addressed, but I will cover those in the next part of the engine restoration story…