Iain's 1970 MG BGT

The Engine Build

This is a picture guide to how I built my engine. Essentially I have followed the excellent guides available at Octarine Services site. Where I have several similar pictures then I have just put one here and linked from that picture to others.

The Bare Block

The block was bored to +60 thous by Entune. Cylinder 4 was sleeved as it was cracked. It was then cleaned until I was sick of cleaning it! A coat of Morris green engine paint from Frosts followed.

The Crankshaft Going In.

The crankshaft was ground to -20 thous. It had previously been ground to -10 thous, but badly needed done again. New bearings and thrust washers were fitted. The picture shows caps 1, 3 and 5 in place. 2 and 4 followed shortly. Have a look at how bad a worn main bearing can look. New bolts were fitted (with a touch of loctite) and the tightened to 70 lbs/ft.

Piston Being Fitted

The +60 thou pistons were then fitted using a piston ring compressor. (More Info)

The new bearings were lubricated with graphogen and then the big end bolts were tightened to 40 lbs/ft. The engine could still be turned easily by hand. There was a little lateral movement of the conrods, but none at all in the direction of the piston travel. I was assured this is normal.

More Cleaning

At this point I returned to cleaning. The front and back plates, the sump, the rocker cover, the front cover oil filter housing etc were all cleaned with soap and water, petrol and the de-rusted with an angle grinder and wire brush. They were then primed if needed and painted green.

More Pics Here.

More Assembly

The camshaft was coated in graphogen and then inserted. The back plate and front plate were attached along with the flywheel. The oil pump, which had been refurbished, was added, complete with strainer. Always take car to make sure that the correct gasket is used, in this case the one for the 5 main bearing engine, not the 3 main.

The sump could then be attached and the engine turned the correct way up. During this period I used a lot of semi hardening gasket compound, hoping to avoid leaks! Once the correct way up all the little bits, such as oil cooler adapter were added. The tappets were then inserted and (again heavily coated in graphogen) and the tappet covers put in place.

Camshaft Timing

It is important that the camshaft opens and closes valves at the correct time. To do this you check when maximum lift is for opening of inlet valve on cylinder one. See the guide at Octarine Services site. 

As I don't have dial gauge I used a set square to work out top dead centre, which allow correct positioning of the degree wheel. Then I was able to use it again to work out max lift. This must be far more approximate than a dial gauge. However, the value that came out was 112 degrees after TDC. This was exactly correct for the information with the camshaft (a Piper HR 270/2). So I decided it was close enough and moved on!

Cylinder Head

I decided to use the unmodified head initially as it was in better overall condition than the gas flowed one I have. Once the car is running I'll get the gas flowed one sorted and put on, and then hopefully sell the unmodified head. The head was cleaned and painted.

The valves were all lapped in and then replaced when new valve stem seals. The head was then fitted, with reconditioned rocker gear, to the block.

The Finished Engine

The engine was then closed up. The dizzy was fitted and statically timed. The clutch was fitted and aligned by eye (which was spot on) , and was ready to put into the car.

Go here for a few pictures of it going in.

Problems With Start Up

The car started fairly easily. It initially showed good oil pressure, but this quickly dropped to a disappointing 40 psi. However, I finished the cam bedding in of 20 mins at 2500 RPM. I then looked into the problem. After extensive consultation it I concluded that the main bearing bolts, which Moss had said were a straight swap for the studs, were actually binding on the threads. This resulted in a false torque reading and the poor oil pressure.

Not a straight swap!