Building up the engine yourself will save money and give you peace of mind that it has been done with care. Having said that if you don't feel up to it or don't have a very clean workspace in which to assemble it perhaps get it done for you.

        Cheap Micrometers use one measuring spindle and several different bodies instead of one for each stage as they come in one inch steps. These Micrometers are however a pain in the neck as you need to fiddle and take it to bits every time you want to measure something different. Cheap and probably totally sufficient ones cost about £20 each, top of the range ones made by Moore & Wright in Sheffield cost £65 each and upwards. In exchange for this they are accurate to 0.0001 inches.

Internal Micrometers cost £100 and upwards each. This is why you use Telescopic gauges.

Dynamic Balancing £90

        What is it? Well dynamic balancing is so called because the rotating components (pulley, crank, flywheel & clutch cover) are balanced by spinning them up to speed on a special machine.

        They will also attach lead shot filled weights to the journals where the con rods are usually placed to simulate their effect. The machine indicates where to add or remove material from the crank counterweights to achieve balance. As standard Triumph engines were not very finely balanced, you will notice a big difference after a pro balancing job. Good balance improves bearing life and makes the engine run more smoothly.

        You should also ask for the con rods to be balanced between each other and end to end if you can afford the extra. The pistons should also be matched in weight to the lightest one. Within 1 gram is the level of accuracy you require.

        The clutch cover is balanced in its place of manufacture but there is no guarantee that the locating dowels for it on your flywheel are perfect!

What is `Blueprinting`? £ lots!

        This is an often abused term, if you get the engine rebuilt it is NOT blueprinted.
Proper blueprinting will be an additional expensive and one not needed unless you are in possession of a good budget and making a race engine. In essence it is thus: Look in your Haynes (or similar) manual and for almost every engine dimension it has a tolerance.
    Example: The crankshaft end float on a 1500 is quoted as 0.006">0.014". Most engine builds will just ensure that it is within those figures. That is fine for a street engine. For a big budget race engine the machine shop will supply the crank end float at exactly 0.010". Not one thousandth of an inch more, or less.

        Imagine a similar exercise in precision applied to each and every single part of the engine, the line of the crankshaft will even be checked to be exactly parallel to the deck top. The bores will be machined exactly 90 degrees to the crank and not just centralised on the old bore holes.

Done properly this is very expensive and not needed for a street engine.

        The next time your mate claims to have a blueprinted engine you can confidently look them in the eye and say 'No you don't!'. The exception to this is if your friend is rich....

How much power can I realistically get?

    A Spitfire engine suitable for easy road use can be modified to produce a maximum of about 55>60% more power than standard. This does not include such things as Nitrous Oxide or any form of forced induction (like supercharging). I regard these options (for the Spitfire engine at least) as alternative means of reaching the same power output as a conventionally tuned engine. If you put a turbo on a 1300 already producing 120 Bhp it would probably either blow it up or reduce its life to under 10,000 miles.

        As you may have noted and were just thinking "hang on you said Terry Hurrells car has 69% more power" remember that his car also has roller rockers and a cam that does require a little more cunning than many would like to drive in traffic. Its up to you and your limits. Nearly seventy per cent more power can be yours but the expense goes up about £500 over the 60% more level and the driveability does suffer a little.

        A three bearing crankshaft (and a long throw in the 1500s case) eliminate the possibility of higher outputs with the sort of reliability needed for street use.

        To my current knowledge the highest power a 1300 racer has achieved with moderate reliability (and short life) is roughly 145 Bhp at the flywheel, about the same is true of a 1500 as the 1300 in race trim can reach 9000 Rpm when prepared correctly. I don't know of anyone running a 1500 even with a steel crank going beyond about 7000 Rpm or so. The MGB was originally made with a three bearing crank before they modified their castings to have the almost universal five main bearings. Moss Europe refuse to build fast road MGB engines with three bearing blocks.

        It simply cannot provide sufficient crankshaft rigidity to guarantee reasonable bearing life. The long throw of the 1500 crank exasperates the problem as the pistons move faster imparting higher stress upon all the main engine components. As you probably know this is one big reason why the racing boys mostly use the 1300 engine, for street use though the 1500 even when modified can be reliable.

The safe mechanical ceiling is well known has been reached, exceed it at your peril (well your Spitfires peril anyway!).

This means that at the flywheel you can realistically expect the following from a well built and carefully assembled engine.

        1300 & 1500 engines: (the TORQUE will be lower for the 1300 but Bhp will be very similar due to a higher Rpm limit on the 1300s). This should not confuse you if you have been an attentive reader and read the later section on what horsepower really means....

- Balanced internals, 9.75/1 compression, bigger inlet valves, fully gas flowed cylinder head, fast road camshaft, duplex timing chain & vernier adjuster, electronic ignition, water & cooling etc. sorted, twin SU carbs with good air filters & decent 4-2-1 tubular exhaust manifold (with the rest of the system too). 105>110 Bhp.

- As above but with Twin Weber 40DCOE sidedraught carburettors: 115>120 Bhp.

- Full race 1300, twin Weber 40DCOEs / Fuel Injection, full engine mods, radical race only cam etc. 130>145 Bhp

        These limits are well known so if your mate thinks he has a killer road going 1300 with 160 horsepower just nod and pretend you're impressed....

What is a dynamometer? (£80 an hour)

        A dyno is basically a big test bed for an engine, the engine is strapped in and run up. This can measure a precise Bhp/Torque curve which is how all the best engine components should be made. They see exactly what effect various components have upon power output.

What is a Rolling Road? (£70 an Hour)

        A rolling road is a machine for measuring horsepower, torque and for tuning the engine under load conditions when the most useful observations can be made. (its difficult to tune the carbs by leaning out the window at 60 Mph).

        The wheels sit on rollers which are turned by the engine. A torque / Bhp curve can be printed off for your engine. Initially the power is `at the wheels` power. This is flywheel power minus transmission, axle and tyre losses. Generally you can deduct 15>20% from flywheel Bhp to get at the wheels power.

        This is the ONLY real means for tuning Weber DCOE carbs and Fuel injection.
SU set ups can be optimised too. Bank for two hours maximum.

        They really push the engine here so fill up with petrol and check oil/water carefully.
You cannot have this done until the engine is properly run in.

What is Bhp and Torque?

        There is much confusion about this and it took me some time to figure out. Bhp is calculated FROM the torque and rpm level. Torque is the actual turning force the crankshaft produces, if you think of putting an imaginary 1 foot long bar at right angles on the end of the crankshaft with some scales on the other end of the bar. Now imagine you had to place 100 pounds of weights on the scales to stop the crankshaft turning. The torque the engine produced would have been 100 LB/ft.

If 300 pounds of weight was required then the engine produced 300 LB/ft of torque and so on.

For practical reasons a dynamometer does not operate quite like that! The theory is identical however.

If you have an engine built by a pro outfit they can actually run in the engine on their dyno so you can drive off as fast as you like with a brand new engine knowing it to be run in and tested.

Bhp is (very basically speaking) the torque an engine produces multiplied by the Rpm.
This is why when looking at a Bhp/Torque curve the Bhp can rise even after the torque has tailed off.

Example: If at 7000 rpm torque is down 5% on 6000 Rpm, the Rpm is 16% higher so Bhp still rises by 11%. Eventually the loss of torque outweighs the rise in Rpm and the Bhp levels fall.

For the mathematically inclined the proper calculation is thus (there are several different methods but all result in the same answer).

If Torque @ 4000 Rpm= 245 LB/ft (a very unlikely scenario for your Spitfire!)

Bhp=245x4000 divided by 5252.

=186.6 Bhp @ 4000 Rpm.

        The figure 5252 is derived from calculations made by a clever Scots engineer James Watt to measure the amount of work achieved pulling horse drawn loads. Therefore ALL Bhp/Torque charts MUST without exception cross at (or in practise damn near) 5252 Rpm. If this does not occur someone is telling you lies!