Daimler 250 V8 engine mods

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Discussion

dave de roxby

Original Poster:

544 posts

194 months

Sunday 20th September 2009
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niva441 said:
As an aside to this topic how difficult would it be to replace the Borg Warner 3 speed automatic with a more modern unit with lock up overdrive top gear? Are there any obvious replacements that would be a relatively straightforward swap.

I looked at one on Friday (bit of a nail, but it got me interested) and would like to know how difficult it would be to make it a bit more suitable for modern motorway cruising.

Thanks
Fortunately for me, my Daimler is one of the rare manual gearbox versions, only 80 or so made, although I am considering replacing that with a modern 5-speed manual.

As far as the automatics are concerned, I can't say for sure. But the Jags used progressively better BW units over the lifetime of the Mk2 range. I guess anything is possible? Hope someone else knows for sure.

dave de roxby

Original Poster:

544 posts

194 months

Sunday 20th September 2009
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If anybody is still interested, further to my thoughts about increasing the capacity of the 2.5 V8, I have just found a factory engineering drawing of the engine and, if it is accurate (which I suspect it is from this era), there seems little or no extra meat to have a go at around the bores. The workshop manual says +40 thou pistons are the max available but, even if I could find some, I think they would be expensive. So I'm stuck with around 2.5 litres max. The valves also look to be as big as the heads will take. So I'm left with gas-flowing the ports. Aside from the inlet system which I plan to completely re-design anyway, one area that looks ripe for attention is the design of the exhaust manifolds. Maybe a few hp to be gained there.

RW774

1,042 posts

222 months

Monday 21st September 2009
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Dave you need to look outside the box on this one. More research is needed via the old drag car boys.You can bore out the old Jag 2.4 to 3.0 litres, an increase of 125ccs per pot, so I don`t see a problem bore and sleeving the 8 to increase bt 75ccs and designing pistons to suite.

dave de roxby

Original Poster:

544 posts

194 months

Monday 21st September 2009
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RW774 said:
Dave you need to look outside the box on this one. More research is needed via the old drag car boys.You can bore out the old Jag 2.4 to 3.0 litres, an increase of 125ccs per pot, so I don`t see a problem bore and sleeving the 8 to increase bt 75ccs and designing pistons to suite.
Yep, you're right about the bores. There I go again, opening my mouth before my brain is in gear! But the pistons might be less easy due to pent-top design - of course, anything is possible. Open to advice here.
Dave

mph

2,316 posts

281 months

Monday 21st September 2009
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If you want to keep the pleasant characteristics of the original engine, then there is apparently very little you can do to improve the performance dramatically.

This is directly from the chap who is the acknowledged expert on these engines Russ Carpenter.

Obviously some improvement can be obtained by blueprinting, mildly raising the compression ratio and fitting fuel injection but I doubt it would be worth it financially for a few extra horses.

A manual gearbox would be my preferred option.

I also considered fitting the Majestic Major engine but there isn't much information out there as to how easy the transplant is.


dave de roxby

Original Poster:

544 posts

194 months

Monday 21st September 2009
quotequote all
mph said:
If you want to keep the pleasant characteristics of the original engine, then there is apparently very little you can do to improve the performance dramatically.

This is directly from the chap who is the acknowledged expert on these engines Russ Carpenter.

Obviously some improvement can be obtained by blueprinting, mildly raising the compression ratio and fitting fuel injection but I doubt it would be worth it financially for a few extra horses.

A manual gearbox would be my preferred option.

I also considered fitting the Majestic Major engine but there isn't much information out there as to how easy the transplant is.
Thanks for that. I'm lucky to have the rare factory manual/overdrive box 250 V8 model but am considering a more modern 5 speed manual box, plenty to choose from. As for the 4.5 Majestic Major engine, have considered this. Although it is obviously from the same family, it is actually bigger and heavier in very respect. The rear end is the same as the 2.5 so theoretically it will bolt to existing gearboxes. But its longer and, more importantly, wider by a few inches. I have heard it can be squeezed into the Mk2 by modifying the inner wings. Prob need different engine mounts, resite radiator etc. But, although initially tempting, think you would end up with too much weight up front which would make it a pig to handle. Siting the engine/box further back would be a major undertaking, even if its dimensionally possible, which I doubt.

Nick_F

10,154 posts

245 months

Monday 21st September 2009
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Would the 4.5 be any heavier than a Jag XK unit?

Otherwise I'm sure it would be possible to come up with a light pressure supercharger setup...

dave de roxby

Original Poster:

544 posts

194 months

Monday 21st September 2009
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Nick_F said:
Would the 4.5 be any heavier than a Jag XK unit?
..
Good thought.

dave de roxby

Original Poster:

544 posts

194 months

Monday 21st September 2009
quotequote all
Nick_F said:
Would the 4.5 be any heavier than a Jag XK unit?
I've been thinking on this again Nick. I haven't found any actual figures of relative weights of the 4.5 V8 and, say, a 3.8 XK but you're right in suggesting there can't be much between them. Also, if the transmissions are in the same location longitudinally, the the C of G of the V8 might actually be further back than the six. Hmmmm. I have spoken to somebody over a year ago who was selling a 4.5 on eBay. He seemed to confirm that he knew it would fit into a Mk2 with some mods to the inner wings so it must have been done. Wish I'd kept his number!!

Nick_F

10,154 posts

245 months

Monday 21st September 2009
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This suggests 400lbs minimum for the Daimler, and a more accurately defined 570lbs or more for the XK including bolt-ons - perhaps not much in it?

dave de roxby

Original Poster:

544 posts

194 months

Monday 21st September 2009
quotequote all
Nick_F said:
This suggests 400lbs minimum for the Daimler, and a more accurately defined 570lbs or more for the XK including bolt-ons - perhaps not much in it?
Interesting link - thanks Nick.

I see a page on Wickipeadia gives 419lbs for the 2.5 and 498lbs for the 4.5. All these figures are, of course, relative to how the engines are dressed.

Carsie

925 posts

203 months

Monday 21st September 2009
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Dave, read your posting with interest smile I seem to recall something about the pistons on a Triumph Bonneville Motorbike being suitable for tuning a Daimler 2.5. I'm sorry I don't remember anything much more than that or the context. By the way don't forget the fabulous story of the Majestic engine being put into the Mk10 for evaluation (as well as the XJ13 Quad Cam of course) - Have fun!

dave de roxby

Original Poster:

544 posts

194 months

Tuesday 22nd September 2009
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Carsie said:
Dave, read your posting with interest smile I seem to recall something about the pistons on a Triumph Bonneville Motorbike being suitable for tuning a Daimler 2.5. I'm sorry I don't remember anything much more than that or the context. By the way don't forget the fabulous story of the Majestic engine being put into the Mk10 for evaluation (as well as the XJ13 Quad Cam of course) - Have fun!


Hi Carsie
Yes, I recall the consternation caused when the 4.5 was tested in the Mk10 and apparently blew the socks off the Jag engined car. However, the idea was swiftly dumped to avoid any damage to the Jag brand' image - or so we're told. There seems to be a lot of mythology going on here which gets reinforced every time the story is told. Same with the 'Bonneville' connection. Whilst there is a general similarity in the piston/combustion chamber shape between the Daimler and this Triumph motorcycle engine (no surprise due to Edward Turner's involvement in both) I don't think there are any actual commonalities between the two engines. I have seen it written that Bonneville pistons were used as the basis for the 2.5 Daimler engine. I'm not sure if this is actually true - anybody know for sure?

However, I have read in a more reliable article re the development of the Daimler engine (Brian Long?) that, at one time, a cam profile based on the Bonny was tried in the Daimler and produced spectacular results.

jith

2,752 posts

214 months

Tuesday 22nd September 2009
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dave de roxby said:
Carsie said:
Dave, read your posting with interest smile I seem to recall something about the pistons on a Triumph Bonneville Motorbike being suitable for tuning a Daimler 2.5. I'm sorry I don't remember anything much more than that or the context. By the way don't forget the fabulous story of the Majestic engine being put into the Mk10 for evaluation (as well as the XJ13 Quad Cam of course) - Have fun!


Hi Carsie
Yes, I recall the consternation caused when the 4.5 was tested in the Mk10 and apparently blew the socks off the Jag engined car. However, the idea was swiftly dumped to avoid any damage to the Jag brand' image - or so we're told. There seems to be a lot of mythology going on here which gets reinforced every time the story is told. Same with the 'Bonneville' connection. Whilst there is a general similarity in the piston/combustion chamber shape between the Daimler and this Triumph motorcycle engine (no surprise due to Edward Turner's involvement in both) I don't think there are any actual commonalities between the two engines. I have seen it written that Bonneville pistons were used as the basis for the 2.5 Daimler engine. I'm not sure if this is actually true - anybody know for sure?

However, I have read in a more reliable article re the development of the Daimler engine (Brian Long?) that, at one time, a cam profile based on the Bonny was tried in the Daimler and produced spectacular results.
You are going down the right road with that now Dave. The Bonneville was an exceedingly good engine, and bike for that matter, for its day. The weak points in your engine as far as power delivery is concerned are the carbs and the exhaust manifolds. Fitting injection and some tubular manifolds will instantly give you a marked increase. Because you are going electronic and changing the inlet manifolds you can also increase the compression ratio by skimming the heads, again this will yield a marked improvement.

Another source of power loss is the mass of the flywheel on the manual version: you can significantly reduce this and make the engine much more tractable vastly improving your throttle response.

Finally I would look at reprofiling the cam, but don't go down the whole route of using the Bonneville profile. Motorcycle cam profiles are designed to give maximum power at very high revs because they are pulling very little weight in comparison to a car engine, whereas with a car engine you need to retain some low down torque to ensure the vehicle is driveable.

I would definitely not fit a 4.5 engine. I have owned at least two Daimlers with manual 'boxes, and the joy of them over the Jaguar was the handling, they are beautifully balanced. The 4.5 is a monster and it will ruin the handling. Remember power is worthless unless you can harness it to the chassis and make the thing go 'round corners!

Interesting project.

dave de roxby

Original Poster:

544 posts

194 months

Tuesday 22nd September 2009
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Wise words Carsie!

RW774

1,042 posts

222 months

Tuesday 22nd September 2009
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I`m amazed sometimes that the average person knows more these days than the factory did back in then! . Let me put you right on the V8 4.5 and Diamler.
The factory bought the company back in the early 60s, to increase their manufacturing capacity and to move into the luxury market.
I too was under the impression that the big V8 was dropped due to the politics of the situation,not so.
Norman Dewis evaluated the Dart firstly, and found the chassis flexed so much at Mira that the doors came open at 90 mph. It was decided early on that the Dart would be low production and subsequently dropped. They also tested the 4.5 in the Mk10 at Mira. It did not blow the socks of the 6,It just did not produce the expected horsepower against the 6. This was despite the factory making various attempts to tune it.Hence it never appeared in a Mk 10 and only remainder in the low volume Majestic saloon and limosine
It was dropped for no other reason, otherwise the factory would have continued production with the 4.5 on a bigger scale, rather than the 800 or so finished cars. After all , Turner had already designed it.It was a `free`product for Jaguar to use .
The smaller V8 was very expensive and remained low volume compared to the Jaguar Mk2 .It was not until the 70s that the 1000hp plus appeared in the 2.5 via the drag racers. Even then the works engineers suggested 200hp max was possible but no more . They had no idea of the strength and quality of the materials used on the bottom end , because by then it was just another old product.What I say Dave is you need to look outside the box on the 2.5, just a the drag boys did back in the 70s.

was8v

1,927 posts

194 months

Tuesday 22nd September 2009
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How about running megasquirt?

dave de roxby

Original Poster:

544 posts

194 months

Tuesday 22nd September 2009
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RW774 said:
I`m amazed sometimes that the average person knows more these days than the factory did back in then! .
Hi RW, Exactly what I was trying to get across in my recent post

"consternation caused when the 4.5 was tested in the Mk10 and "apparently" blew the socks off the Jag engined car. However, the idea was swiftly dumped to avoid any damage to the Jag brand's image - "or so we're told". There seems to be a lot of "mythology" going on here which gets reinforced every time the story is told. Same with the 'Bonneville' connection. Whilst there is a general similarity in the piston/combustion chamber shape between the Daimler and this Triumph motorcycle engine (no surprise due to Edward Turner's involvement in both) I don't think there are any actual commonalities between the two engines. I have seen it written that Bonneville pistons were used as the basis for the 2.5 Daimler engine. "I'm not sure if this is actually true" - anybody know for sure?

However, I have read in a more reliable article re the development of the Daimler engine (Brian Long?) that, at one time, a cam profile based on the Bonny was tried in the Daimler and produced spectacular results."

Yep, a lot of crap gets put in writing by journalists and contributors alike. Trouble is, it gets taken in as gospel then gets regurgitated as a good story and the myth is established to confuse good souls even 50 years down the line! That's why I'm treading carefully here.

Anyway, as interesting as this all has been, I'm sticking with the 2.5, I am going to look at sleeving to up the capacity as you suggested but am still uncertain about pistons to suit, I am determined to build my own inlet system with fuel injection, will look at the heads and exhaust manifolds and go from there.

Always good to hear from you! Dave.

RW774

1,042 posts

222 months

Tuesday 22nd September 2009
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Top man, thanks for that.

dave de roxby

Original Poster:

544 posts

194 months

Wednesday 23rd September 2009
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was8v said:
How about running megasquirt?
Thanks was8v, Yes, a number of contributors have mentioned megasquirt and I am checking this out.