Daimler SP250 Restoration

Chassis

Ths Chassis was in excellent condition with only minor surface rust. After sandblasting it was checked for straightness, then some strengthening welds were added in certain locations. Once done it was then off to the paint booth for painting in 2-pack black.

Since painting and reassembly, and prior to refitting the body, the rear sections were boxed in and painted. Steel plate was cut and spot welded in position, with the ends mig welded to the main chassis rails for additional strength. Coupled to the rear cross brace used for the rear telescopic shock absorber conversion, this should help minimise chassis flex.

Gearbox

The gearbox was in excellent condition. It was thoroughly cleaned, with new front and rear seals installed. The gear lever was rechromed and the other mechanical parts including any nuts and bolts were zinc plated.

Clutch

While the original pressure plate appears to be in good condition, I have decided to replace it with a diaphram type. This necessitated redrilling the flywheel to suit the new pressure plate as well as new dowels. The pressure plate was sourced from a Landrover. The pressure plate and flywheel have been dynamically balanced with the crank and other engine parts.

Engine teardown

While the engine had been previously rebuilt, sitting idle for 40 years dictated it be stripped for inspection. It was just as well, as there were a number of problems detected. Nothing major, but a full rebuild is currently underway. This will include new valves, springs and guides. The block will be taken to +20 with new 9:1 compression pistons. New bearings, timing chain, gaskets, and a balance including the clutch pressure plate, and it will soon be ready for reassembly. All external aluminium components including valve covers, inlet manifold, sump have been vapour blasted.

Engine Rebuild

The aim of the rebuild was to build a basically standard engine, but to make a few minor tweaks here and there to add a few extra horses. Porting the inlet manifold, fitting 9:1 pistons in place of the standard ratio of 8.2:1, and balancing all components, including the flywheel and clutch assembly, should provide a smooth revving motor with some extra zip.

To begin, the block was chemically cleaned, then bored +20 as one of the cylinders was scratched. New 9:1 pistons were fitted. The crank was stripped and cleaned internally, then ground, and fitted with new bearings. The heads were overhauled with new springs and valves. The cam followers were replaced as most of the originals were worn. The oil pump was overhauled and the relief valve adjusted to allow for a slight increase in oil pressure.

Two pushrods were replaced as there was some damage to the originals. The head studs were replaced with new bolts. A new timing chain and tensioner were also fitted. The tappet covers were cleaned and polished and refitted along with the exhaust manifolds, which were 'jet-hot' coated in matt black. The final result looks terrific. I can't wait to fire it up for the first time. 

Rear Axle

One of the first components to be rebuilt after the chassis strip-down.  After sourcing some new rotors it was sent off in early 2017 to be professionally overhauled, with new seals, bearings etc. No major issues were found, and once rebuilt it was painted in 2-pack red and black..

Front Suspension Teardown

Dismantling the front suspension was straightforward. The only challenging part was removing the front springs, which are under huge strain, and for that I used a spring compressor.

All components were in good condition, although the trunnions had seen better days. These will be replaced, along with all the bushes. The uprights are in excellent condition, the threads look perfect. All components will be sandblasted, painted in 2-pack black pror to reassembly. The hubs and bearings will also be replaced as I will be converting the car to wire wheels.

Front Suspension Overhaul

Each component was checked for any damage and thoroughly cleaned. I have a sand blasting cabinet at home so this came in very handy. Once clean they were again inspected before being taken to All Classic Cars to be painted in 2-pack black.

I fitted a new ball joint and bushes to the upper wishbones. For the lower wishbones I fitted new rubber bushes, but the brass bushes which slide on the trunnion were in good condition and were over-size, so they were reamed to suit the new trunnions. While al this sounds simple it took some time, especially as I had not done this before. I learnt how to do this on youtube (as you do tese days) and all I needed to do was buy the correct size reaming tool. 

Once the reaming was complete I pressed in new rubber bushes at the opposite ends and began the reassembly. I greased the upright with a Castrol Spherol high pressure grease, and threaded it into the trunnion, along with new seals. The lower wishbones were then attached the the trunnions, also with new seals. All the nuts, bolts, mounting hardware and camber shims were zinc plated and reused. As for the original shock absorbers, these were past their best and were leaking, so I purchased new Spax adjustable shocks from David Manners. These match the Spax adjustable shocks that I am using at the rear.

The springs were sent away to be professionally sandblasted before being painted in 2-pack black. At this stage I had not yet 100% certain that I would fit wire wheels, so I cleaned and painted the original hubs, and fitted new bearings. This would at least get the chassis mobile until I made up my mind which way to go.

Front Suspension Refit

As they say in the workshop manual refitting is the reversal of the removal procedure. Everything went well, however once back on the ground it was obvious that some adjustment to the camber and ride height was needed. 

These cars were originally set with 2 degrees positive camber. As I am changing the steering to rack and pinion, I understand the ideal camber for this setup is 0 (zero) degrees. I borrowed a camber setting tool from Tony  Pallas at All Classic Cars to enable me to set the suspension as accurately as possible. It was soon obvious that I would need plenty of shims. I cut these out of scrap steel and aluminium of varying thicknesses. To make it easier to add and remove the shims I disconnected the steering tie rods and lowered the spring pan. This takes all the tension off the lower wishbone, which allows it to be separated from the chassis giving it a nice wide gap with which to add new shims. The rule of thumb I discovered is roughly 1mm shim for a quarter of a degree. It took several goes on each side to get the camber I was looking for. I became very adept at installing and removing the springs, and could do it in a few minutes. The use of short lengths of high-tensile threaded rod in place of the lower spring pan bolts made things much quicker and simpler than using a spring compressor. 

Wih the camber set to 0 degrees, it was time to do something about the ride height. Since putting the body back on the car it was quite noticable how high the car was sitting at the front - probably about an inch or so too high. The body was sitting down on the chassis, which to me indicated that something wasn't right with the front springs. I decided to source some new springs from David Manners and to see if they made a difference. As I was removng the springs to set the camber, this was the perfect opportunity. I removed both springs and compared them to the new ones. They were both exactly the same height. Interestingly the original springs had 9 coils and the new springs had 10 coils. To my way of thinking this would indicate the new springs were slightly softer than the originals, which may compress a little further than the originals. With nothing to lose I swapped them in and lowered the car back on the groumd. I rolled it backwards and forwards a few times to help things settle, and then took a measurement to the top of the wheel arch. The car was now sitting approx 25mm lower than before, and looked pretty close to being right. The bonnet, doors and seats are yet to be fitted, so I'll see what it looks like once that's done and the car's been on the road for a while. I can only think the reason for it sitting too high is the front springs have had next to no weight on them for the past 45 years.

Refitting the body

The 10th July 2020 was a significant day in the restoration of 102631. It's the day the body and chassis were finally reunited! The car was dismantled sometime in 1975 and has been apart since that time. That's 45 years! Did the original owner back then imagine it would be apart for so long? 

First of all the body was placed on the hoist, and the timber frame it had been bolted too for the past 45 years was removed. The chassis was then rolled into position. After confirming both were lined up, the body was gradually lowered. A few minor adjustments of the body and chassis during the final moments saw both come together quite quickly. the process was over in less than 20 minutes, and best of all not a scratch on either the body or the chassis!