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MG MGB Technical - Mgb gt cgrome 1974 cylinder head removal

Hi back again..
After successfully installing a new 12v instead of 2 x 6V's, which has worked brilliantly, Starts first time. Replaced Rocker cover seal and nut attachment. I am at the stage where through friends and experienced mechanic, the pressure in one of the cylinders is 0!, so we are at the stage of looking at removing the cylinder head and pistons!. I have a friend who can refurb the head and pistons for good price, but only if I take them off.

OK from my point of view I need to know the best and easiest way to remove head and pistons, as I know I have to get under the car and drain the oil and remove the sump!..

I have the jacks and ramps ready to go, so a good explanation of were to start from would help.

Just a query on the engine the side of the carbs, we have noticed that, there looks like a cardboard heat deflector, that we think is asbestos!, is this the case and what is the best way to handle this..?

Thanks again on any tip or tricks to sort.

Jim

J Giddins

Hi Jim

Yes. the backing on the heat shield is asbestos. I spray mine with a mist of water prior to removal and am careful not to disturb the material when I remove it.

Asbestos is only hazardous if breathed in, normally over periods of time. Remember that most brake pads also had asbestos Some still do.

I have seen listings on the post about non-asbestos substitutes for the heat shield, but if you just use some caution, it should not be an issue.
Bruce Cunha

I would suspect a burnt out exhaust valve or broken spring. Taking the head off should take about 2 hours. Taking the pistons out with the engine in situ may not be worth the hassle.
c cummins

Hi Jim,

As stated, above, removing the head is no big deal, tedious yes.

First you need your workshop manual and have a good read of the section dealing with the head.
Jack the front of the car up and put stands under it. Leave access to the sump clear.
You need to drain the radiator. Place a large bowl, at least 8 litre capacity, under the drain cock , remove the radiator cap and open the cock. If no water comes out you will need to remove the bottom radiator hose. Water will splash around when you do this, but most will go into the container.
Drain the oil, leaving the sump plug out for a while to fully allow the oil to drain.
Remove everything from the head, manifolds, heater control valve, temp sensor (carefully, if the capillary type), top radiator hose and what ever else there is.
Remove the head nuts, in the reverse order that the manual says to tighten them.
Give the head a short sharp whack with a mallet or similar, not a steel implement, to break the gasket seal. The head should now lift off. If it doesn't check the manifold studs. On my B they had been replaced with threaded rod and screwed in real tight, acting as grub screws on the head studs.

Place a large piece of cardboard under the engine. If you don't have this cardboard, shout the family to a new 42" TV and use the box it comes in. This is to protect the floor from oil drips and spills.

The sump comes off fairly easily. From memory youwill need a tube spanner to extract the rear screws, from between the sump and rear engine plate. The front screws are also a bit difficult, as you need to access them over the top of the cross member.
The sump needs to be wriggled about a bit to get it past the oil pump.
Once the sump is off you have access the the big ends.
Mark each rod and shell with 1, 2, 3 & 4 dots, respectively, from #1 to#4 cylinders, so that you can replace them correctly when reassembling.
Push the rod up, using a wooden rod (hammer handle) so that the rings pop open. Now the piston will not slide back down.

To reassemble you will need a ring compressor, and a ridge cutter, to remove the lip at the top of the bore.
Before inserting the piston in the cylinder turn the crank so that the corresponding journal is at the bottom and place some cloth around it to protect the bearing surface from the rod as it comes down. Ensure that the pistons and rods are correctly oriented before inserting. Also oil the inside of the cylinders and the piston and rings prior to inserting.
Replace everything in the reverse order, and your done.

NOTE: If you have damaged cylinder walls or crankshaft journals the engine will need to be removed and rebored and the shaft reground. You will then need oversize pistons and bearings.

Herb
Herb Adler

Pull and inspect the head first before committing yourself to piston removal. As already mentioned, it could merely be a burnt valve that is causing 0 compression. I pulled the head on a Mercedes Benz 300D, with a similar problem, and it turned out that half of one the intake valve heads was missing. RAY
rjm RAY

This thread was discussed on 20/11/2010

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