Engine assembly 2.

The plan and the main non-standard components

There are hardly any "standard" Cooper S engines in the world. And that's not mainly because they were not built well by the factory, but rather due to the fact, that thees cars offer  LOT more fun if given that very little bit of "extra".

Soo ill we modify our engine? Definitely. When doing soo, one must be careful though. It is far too easy to make a dyno-day-only car, that will be awful to drive. Our goal was to "finish" the factory treatment and develop the car in a manner the factory should have done if only they had the components, and the extra money to be able to do it.

The non standard components are mainly on the picture. The cylinder head was slightly modified at a point, but was done not quite well. Now I reshaped the ports, and generally finished the factory design. I did not opened up the ports too much, rather I only reshaped them to get a more unrestricted airflow, but not to slow down the gasses. Std valve sizes were kept, but the seat were given a 3 angle grind to better the flow at partial lift situations.

To achieve some extra at mid and top range, a bit longer duration camshaft was used with a modern, more aggressive valve timing profile. To work with this camshaft, a special valve spring set will be used.

On the intake side, a Kn filter will be used to better the intake,and a freeflow, 3-2-1 long central branch manifold, with a medium bore RC40 exhaust system made of stainless steel will be on the exit side. This system gives a modest note, but quite nice on power, especially on mid range torque. Although the manifold looks quite nice, it will be covered in heat insulation to keep the heat at bay.

All thees nicely set up, will develop a healthy 85-90bhps. 

We also have some parts to better longevity and general reliability. We will use a superb cometic head gasket, and spec higrade cylinder head bolts and nuts to prevent gasket failure, which is quite not unheard of with big bore mini engines. Arp studs we use at the main and conrod bearings, new oil cooler and pipe will be there to protect the new engine from old debris left in the 40+ years old cooler.

Engine assembly 1.

Assembling an engine is always a delicate and delight full task. First in the row is a THROUGH cleaning, which takes quite some time. The engine should realy be as clean as possible before I check the tolerances and start the building session.

After cleaning the parts and the block, I have measured everything around the unit and checked if all tolerances fall between the factory specifications.

Engine Build Sheet

Camelot Restorations

Project:  Cooper „S” Mk3 WP	Displacement: 1293ccm
Engine type: A series, cooper S	Compression ratio: 1:9.75

Piston-bore clearance	1.	2.	3.	4.	5.	6.	Fact
	0.04-	0.04-	0.04	0.04+			0.035-0.063

Piston ring side clearance	1.	2.	3.	4.	5.	6.	Fact
1.	0.05*	0.05*	0.05	0.05+			0.04-0.06
2.	0.05*	0.05-	0.05	0.05			0.04-0.06
3.	0.05	0.05*	0.05	0.05			0.04-0.06
4.

Main bearing clearance	1.	2.	3.	4.	5.	Fact
	0.06	0.06+	0.06+			0.035-0.075

Big end clearance	1.	2.	3.	4.	5.	6.	Fact
	0.05	0.06	0.05+	0.06			0.035-0.075

Valve clearance	1.	2.	3.	4.	5.	6.	7.	8.	9.	10.	11.	12.	Fact
	0.06	0.05	0.05	0.05-	0.06+	0.05+	0.05+	0.06					0.05-0.075

Crankshaft axial free play:  0.14

After checking the tolerances, I balanced the con rods and the pistons. Con rods are end-to-end within 2 grams to one another. Total weight is 739g in average. Pistons are also 2 grans from each other, weighting 357g without the rings, and 377g with the ring pack average.

Gearbox 5.

After a bit of lamenting, we went for 3.44:1 final drive as a balance of cruising and acceleration.

The differential pin is an item that is also prone to wear. For longevity we went for competitions grade replacement.

Diff side covers get distorted quite common.

Some hand filing was necessary to restore the mating surface.

Diff bering preload is set by shims on the mini gearbox.

Gearbox 4.

The old layshaft was worn, which is quite not unlikely as theese shafts take quite some load.

To avoid such premature wear, we went for a hi grade replacement.

Minis have a construction problem around the oil pickup pipe. As the sucking end of the pipe is located on the left side of the case, in a longer left-hend curve, the engine might suffer from oil starvation. To prevent this, it is adviceable to replace the original item with a central oil pickup type.

The oil pump is also an item that usualy has short service life in a mini engine. The reason is also  costruction related. The engine shares the oil with the gearbox. There are always metalic particles in a gearbox it is part of their "normal" operation. Unfortunatly the oil pump is before the oil filter in the circuit, soo it sees unfiltered oil. To lessen this problem. I put this little gadget in the oil line. This is a small filter with a magnet. If this part is looked at from time to time, the oil pressure will stay strong much longer. 

An often overlooked item: the selector oil seal. 

A very slight preload is necessary on the shaft bearings

Gearbox 3.

For the best results, we went for a complete gearbox and differential rebuild kit, which was by no means "complete", but most of the usual wearing parts were there.

Original bearings were metal case, but theese plastic case items are just as good if not better as the originals.

A place hard to check: the inner bearing surface if the primary gear shaft. This time it was in perfect condition.

Gearbox 2.

After preparing the parts, I started building the unit.

First the selectors go in.

The selectors are held in position in gear and neutral by theese items, which end in a ball. They need to move free and need to be held tight by their springs in order to make the gearchange feel all right.

The springs sit behind their securing bolts. Theese bolts are sealed with copper rings. In order to make them seal, I heated them before instaling.

You have to pay attention when fixing the selector forks onto their shafts. They have to be in perfect position, unless You will end up with a pudding stearing like gearchange and sooner or later a destroyed selector shaft.

The reverse gear shaft was checked for straightness and wear.

No problem was found, soo I installed the assembly.

Gearbox 1.

Although we did not have the correct original gearbox in the car, luckily we had an Innocenty Cooper Export unit, which is identical internaly as the original, just in a rod change housing. This gave most of the hard-to-find parts for an original setup. We also needed a remote change 4 syncro gearbox case, and some internals. Luckily I had one in my shed, collecting dust a few years now. This is 90%. The rest 10% was a bit of a problem. The Inno had the late pot type inner driveshaft joint, the 4 syncro came from a plain 1000ccm modell, thus had the rubber cross type, unlike the Cooper S, which had the hardy spicer joint. The parts that are available new, we bought, but still there are 3 parts that are not available of the shelf. Theese we got from a mini racer, whom we are very gratefull for this, and as soon as possible we will give them back :-).

Rebuilding the gearbox on a mini is not a one afternoon job, and although it might look easy, need a bit of attention at some points. Especialy if You would like to do it only once.

First I cleaned everithing. This time I took a chance with the dishwasher. Although it was technicaly a success, I am not sure how many times the Wife will forgive it to me.

I have a couple of dismantled gearboxes, I wanted to pick the best parts with as few wear as possible. Take care: 3 syncro and 4 syncro box parts might look similar, but they are not always interchangeable (dont ask me how I learned this).

Nice clean case just out of the paint cabinet. Case inspected for damage on the sealing surfaces, at the bearings and at some places for cracks. 

With some parts the condition is obvios, but some parts need to be investigated quite close.

All the gears inspected outside...

...and inside for wear.

Old sycro rings were definitely worrn. Look at the gap between the ring and the gear here...

...and here with the new item.

As a final point the gearbox mainshaft was checked for straightness.