Here’s how to make your daimler v8 – saloon or sports car – great! words by alan anderson images by magiccarpics.co.uk & classic motoring

Daimler may have made dowdy cars back in the 1950s and 60s but the company’s V8 is an all time classic and can give tremendous power for surprisingly little effort. In this Road & Track special, we look at both the SP250 (Dart) roadster and the Jag Mk2-bodied V8 250 and how to make them fly.

What about the V8 250? This Jaguar shares the same engine as the SP 250 so the same rules apply, although it’s said that cooling under the Jag’s bonnet needs more of a watch and this will be more applicable if you shoehorn in the larger 4.5 version. Handling is inherently better in standard trim and taken care of by uprated dampers (Gaz and Spax are liked) along with sportier springs, polybushing and good tyres. The more adventurous might like to fit the front axle from the 420 and gain better steering and brakes (or go to Classic Spares and buy straight fit modded ones at £450). Watch the spring rates though as the V8 was lighter than the XK unit. Also, as most saloons were automatics, consider converting to manual or seek out an automatic transmission specialist who can revise the gearbox’s change up points, although it can be tricky. However you tune your V8 250, done right it will beat the pants off a 3.8!

Before You Start

Rust is the main concern with the Dart despite the convenience of a separate chassis. Basically they rot just about everywhere but cross-members, beams suspension points and turrets are the most crucial regions as is the location of the steering box, although replacements are
available.

The sectioned chassis will rot; usually at the suspension pick-up points (especially the front wishbones) and where the rear axle is located. Rear crossmember needs a regular watch, along with the rear spring hangers, which are hard to get at. New chassis were available until a couple of years ago and you may stumble across one.

That renowned V8 is as long-lasting as well as sweet. Lowly oil pressure (you need to see in the region of 40psi), general decay and hot running, due to corroding alloy waterways, can occur and need sorting before tuning. A full rebuild is likely to run out at £5000 but it’s worth doing properly as the engine used high quality materials during manufacture.

Hotting One Up

The Turner V8 is an all time great and has considerable performance potential – well over 1000bhp! You won’t want to go that far as this drag racing spec and British Leyland wrung 200bhp from the unit but said above this it became unreliable – something else perhaps BL got wrong?

In standard tune, the unit benefits from a good electronic ignition to do away with the quirky twin-points set up. This along with fine tuning on a rolling road should net another couple of bhp above the standard 140 horses for minimal effort.

As is well known, the V8 is closely related to the BSA Speed Twin Turner also designed and the ‘hemi head’ was very advanced for its day.

Unleaded valve seats are not needed as they are already hardened from the factory because of the aluminium heads. All is needed for unleaded is to replace the exhaust valves with stainless items. However, good practice would be to replace the valve guides with modified ones using stem seals at the same time, as originally seals were not fitted here and thus can lead to oil burning problems.

Even if you don’t intend to tune the unit, cooling can be a problem and after ensuring the system is tip-top, an electric cooling fan is advisable.

We spoke to leading SP250 expert Philip Glennerster who runs Autotec (01189340927 http://www.autotecsp250.co.uk). He says around 160-170bhp, achieved by gas-flowed heads and better carb jetting (or better still, four Amal bike carbs but you’ll have to have a manifold made up) is the best mix for most owners. Racier camshafts are available (based upon a Triumph Bonnaville profile) but also rob the engine of its low end torque.

This advice is echoed by Russ Carpenter (01483570632), who is the font of all knowledge for this engine and once tuned one up to an amazing 1500bhp for his dragster – and most of the engine’s internals remained standard!

Russ says tuning anything much above 160bhp and the engine invariably becomes “grumpy” and loses its smoothness and flexibility for road use.

What he does advocate is gas-flowing the heads (the valve sizes are fine) and skimming around 40thou to raise the compression ratio; this inexpensive mod nets some 10bhp he says.

The design of the exhaust manifolds is okay says Carpenter, less so the inlet which is rather crude and causes uneven mixtures across the engine bank. It’s not easy but cleaning up and flowing the manifold ports pays dividends. The standard SU carbs are ample and there’s not much of a gain going up to 2in ones adds Carpenter.

For many, in a light roadster, this provides ample performance but there’s much more on offer if the bottom end needs overhauling. Although Glennerster has no experience of such mods, he knows that the engine provides tremendous scope for over boring where well over 3-’itres has been achieved, using Triumph Bonnaville pistons, which are also of a higher compression, giving around 10.5:1, plus allow an overbore of +60thou. One owner claimed he went as high as a 156thou rebore albeit with specially made pistons!

Carpenter has tried this trick in the past and while it works, he is now sceptical, saying that today’s reproduction pistons aren’t as good quality as the Triumph ones. He also advises against using a Bonnaville profile camshaft and recommends the milder Piper BP270, if you can find one.

Of course as Daimler also made this engine in 4.5-litre form, why bother when there’s an easier way to get more go? In stock tune, Daimler quoted a conservative 220bhp for the unit, chiefly because the factory’s old fashioned engine dynometer wouldn’t read any higher where as Jaguar was always optimistic over its power figures. What is fact is that when the
4.5 was slotted in a Mk2 and Mk X they went like stink!

Slotting in the 4.5-litre is straightforward (indeed Daimler did it on a selected bunch sent to the US, apparently) but not quite as simple as many believe, being slightly longer plus it doesn’t bolt straight on to the Triumph-derived manual gearbox; you ideally need a Jag (Moss) unit. Another problem, says Russ Carpenter, is parts supply which he says was poor even back in the 1960s; in contrast parts for the 2.5 are plentiful.

Talking of transmissions, Phil Glennerster is not an advocate of fitting the Toyota Supra five-speed manual, although kits are available and prefers to keep it traditional. “I use a Laycock overdrive – either A type or J type (mostly J type now) as both fit neatly on the original Dart box with very little modification needed. An overdrive was offered as an optional extra originally, but I believe that none were ever fitted at the factory. The Jaguar gearbox with the overdrive (as used in the V8 250) can be fitted but requires quite a lot of modification including the sump (as the starter motor fits closer to the engine when using the saloon’s bellhousing and engine plate), and the propshaft needs shortening”, he told us.

Handling The Power

Autotec advises replacing the front suspension wishbone bushes with polyurethane types coupled with adjustable front dampers. At the rear, while uprated lever arm dampers are available and work well, converting the rear to telescopic adjustable shock absorbers at a cost of just over £300 + fitting is the better option. For those tuning the engine, rear anti-tramp bars (£300 + fitting) are almost a must.

As for tyres, Phil recommends not being a wide boy; 165 or 175 or 185 radial is the maximum width in his opinion as any wider may give problems with the tyres touching the wheel arches.

The Dart’s steering was always a bit of a downer but what you can do is fit a crisper rack and pinion conversion. It’s not cheap however, costing £1560 it takes 23 hours to fit claims Phil.

The SP250’s brakes on the other hand need little uprating as discs were fitted all round. EBC Greenstuff pads and a better modern servo are all that you need says Glennerster although EBC’s Turbo discs are worth fitting if the existing ones require replacement. Philip has one final mod up his sleeve. As is well known, the original Darts were too floppy and this was largely cured on B and C spec variants. You can go further by replacing the three rear chassis bars with small box section steel. It’s a bit extreme for road use and this would only be required if the vehicle was being used as a rally or track car using more power. Typical cost is £300 from Autotec.

Hotting Your Car Up

BUDGET

* Sports air filters

* Electronic ignition

* Cylinder head skim

* Rolling road tune up

* Piper camshaft swap

FULL THROTTLE

* Attention to inlet manifold profiles

* Overbore (over 3-litres)

* Fitting (Majestic) 4.5-litre

* Consider supercharging?