Daimler 250 V8 engine mods

Author
Discussion

v8250

2,724 posts

210 months

Wednesday 10th February 2010
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that's a real nice set-up. be very interesting see the cfm figures for this...


RW774

1,042 posts

222 months

Thursday 11th February 2010
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Now that is class.What management is it running.

Dart

3 posts

169 months

Thursday 11th February 2010
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Hello
I am the Dart owner doing the injection mods to the 2.5 V8 as seen in the post by Geeman on Tuesday, just found this thread and registered on Pistonheads today.
As usual in these forums there is some good advice from people who have done it, well meaning advice from those who haven't, there is some myth, some conjecture and some total rubbish. All good fun etc which is why we all do it. Unfortunately Dave de R aint getting much done.

Some of the questions that I have addressed on the V8 are;- steel 4 bolt mains caps, front and rear crank seals, changing main bearings without splitting engine and gearbox. Bike throttle bodies, T/B to head manifolds, sensors for air and water temp, crank revs, throttle position, lambda etc. Bonneville cam profile gas flowing and larger valves. Aftermarket ecu and rolling road mapping. If you keep the auto box the engine needs to be mapped on an engine dyno before bolting into the car.

David de Roxby - if you want to PM me and I will send you my phone number we can have a chat.
I have collaborated with Russ Carpenter for many years about bits and mods for this engine and am just finishing my own set up, so feel I can talk with reasonable authority about it.
Regards John

aeropilot

34,296 posts

226 months

Thursday 11th February 2010
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v8250 said:
that's a real nice set-up. be very interesting see the cfm figures for this...

Nice.

Hilborn, Jenvey or someone elses system....??


dave de roxby

Original Poster:

544 posts

194 months

Sunday 14th February 2010
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Just wanted to say a grateful thanks to Geeman 237, v8250 and Dart for finally leading me to the experience and information I needed to get on with my project. Will be in touch soon. This thread has produced some interesting banter and I've learned a lot - thanks to all.

Priority now is to get on with selling a house which will provide the dosh for my retirement. The Daimler engine is already on the bench, waiting for a strip-down but will have to wait now until around June I guess before I can proceed. Meanwhle, I finally have some reliable info to grapple with and some calculations to do.

Cheers for now,

David

CCDbriz

4 posts

169 months

Sunday 14th February 2010
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Hi folks
Just found this thread while idly googling daimler v8s.
I've had an interest in these engines for 20-some years and am currently building a motorcycle around one. Yeah, OK.
Anyway, I thought I'd clarify the situation about using Triumph motorcycle pistons. I've just had my block bored to accept a set of these.
The pistons needed are 750cc Triumph T140 LOW (8.5:1)compression.
The Triumph heads have a much deeper domeed combustion chamber than the Daimler so even the low compression slugs have a higher dome than the stock Daimler ones. If you use high-comp Triumph pistons, you'll end up with a ridiculously high compression ratio.
Since I have them to hand, I took some pics to compare:

As you see, the Triumphs are shorter, about .060" at the top (start of dome) and about .250" at the bottom. Internally, they're a lot more sturdy.
Stock Triumph bore size is 76mm, and the Daimler is 3". About .008" difference. To accept +.060 Triumph pistons with .003" clearance I had my block bored to 3.050"
Regarding big-bores to increase displacement, I took a close look at my block and did what I could to determine the thickness of the castings around the bores. Looks like theres a good .250" to play with.
I reckon you could get away with boring out to 80mm leaving a thickness of around .150". A bit on the thin side but probably OK given the (reputedly) high quality of the iron used in these castings.
Hope this is of some help. And if you want to follow progress on the bike project, its here:
http://www.britchopper.co.uk/forum/viewtopic.php?f...

Dart

3 posts

169 months

Sunday 14th February 2010
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David
I await your email.
CCDbriz
You will find the 9.0 to 1 T140 pistons top ring land is about 0.5 mm short of the block deck if you leave the block as standard. This by my rough calculation and memory, (25 years ago when I used them on my first rebuild on a Dart), leaves the comp ratio at 8.6 to 1, a bit up on standard.
The max bore is 60 thou for reliability, however if you want capacity, it is possible to go to a stroked crank and get up to 3.2 litres. You are then opening another can of worms with piston top / deck height and shorter rods etc. Possible but only sensible if you have very deep pockets.
If you want serious performance go injection, twin turbos, full management and forged flat top Triumph car race pistons (TR5/6). The grunt is then from a high blower pressure, mild cam, intercooler and proper mapping.
Bearing in mind the standard crank, rods and flywheel are steel, why get rid of them? The restriction on this engine is the intake manifold and SU's. I am looking for 200 to 230bhp on injection and if Audi can get 800hp with a 2.2litre 5 cyl then 400+ with a 2.5 V8 should be do-able.
John

tevie54

2 posts

170 months

Friday 12th March 2010
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Aha, i knew the Triumph pistons fitted, having lighter stonger pistons will give a welcome power increase.Would gas flowing the heads help as well? If the car is going to be used mainly on the road then having a smooth tractable power delivery is paramount, its all very well telling Dave to turbo/supercharge/nitrous his engine but if wont tick over at the lights then its just not practical. Personally i would concentrate on lightening and balancing the internals, increase the compression, improve the gas flow through the heads and exhaust manifolds and then look at a suitable fuel injection system to finish it off. There's been enough info on this site to help with which system to go for.

Hooli

32,278 posts

199 months

Saturday 13th March 2010
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Interesting thread guys. Just a few points as I've recently rebuilt a T140 Bonnie engine.
8.6:1 is normal UK compression ratio, there is a higher one & some US spec engines run about 7.4:1 - so asking for low comp could well get you the wrong pistons. I've seen +80thou pistons offered, but most makes go up to +60. Harris seems to be regarded as the best make.
Cams - which one? the traditional Bonnie cam is E3134 profile. There are others though, however E3134 is regarded as the best for inlet & exhaust for tweaked road bikes - T120s run this anyway but a weak bottom end meant the T140 had a much softer 'saint' exhaust cam.

Oh, I get all my bits from Wilemans in Derby. They seem to know everything about Bonnies, not that that'd help much in this quest.

Edited by Hooli on Saturday 13th March 01:59

Stevepolly

204 posts

65 months

Sunday 4th April 2021
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Eleven years on and no updates?
Anyone know the people involved here and did anything get taken forward?
Steve.

Huntsman

8,026 posts

249 months

Friday 9th April 2021
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I thought of this thread today while wondering about converting a 2.5 saloon to manual box.

kimducati

342 posts

163 months

Saturday 10th April 2021
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Huntsman said:
I thought of this thread today while wondering about converting a 2.5 saloon to manual box.
IF you can find someone who knows what they're doing, the auto box can be modified to give a much more positive operation.
Back in the day, when I had one of these engines fitted in a Mk1 Escort, I used a high stall torque converter and uprated brake bands and changed the internal valves inside the 'box. I was, however, lucky enough to have my dad, who knew how these things worked, and worked for a forklift truck / loading shovel manufacturers who used the BW 35 as their gearbox of choice, with all of the uprated bits.
Maybe nobody left now who knows about these things?
Kim
ps You still have some losses, of course, but the ability to just mash the pedal to the floor in conjunction with the modded torque converter was a big advantage away from the traffic lights!!

a8hex

5,829 posts

222 months

Saturday 10th April 2021
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anonymous said:
[redacted]
If you can get as far as the Jaguar box and the budget isn't too much of a worry then you can get a 5speed box which is bolt compatible, it was originally done for Guy Broad but I think you can get it from other suppliers now too. I got the one for my XK150 from Winspeed. It's based on MT75 internals.