The engine overhaul

This article concerns the 2600 Rover SD1 engine. I bought a 2600 as a non-runner. So my first aim was to get the engine running again. The first checkups showed me that 2 of the 3 elements for a combustion where there. Logically air was one of them, the other where sparks. I did not check if it was timed properly, because the mayor part for firing up was missing, fuel!

At first it needed a complete carburetor overhaul, a good cleaning job and fitting new needles etc, not much work really. After turning the engine several times on the starter, the engine fired up. Since this was my first project on a car, and I did not have any engine adjustment tools at that time, so we decided to take the car to the Rover dealer where proper setting up of the engine was done for us.
Two weeks later, a sad message returned from the garage with a note saying; “it is not possible to adjust the engine, due to no compression at all in cylinder nr. 4, and less in nr. 3 and 6.”
Unfortunately the carburetor overhaul was not the main problem for a none running engine…. This was a more serious problem!

At first, I did not believe the dealer; he must have made a mistake, well, that’s what I had hoped for. I bought a compression tester to measure these figures. When you add some oil on top of the pistons, there is no air passing the pistons in the bore. The only leakage you can measure is from a none closing/burnt out valve. The measurement made it clear, the Rover dealer was right and the problem came from the cylinder head not from the pistons or piston rings.
I decided to remove the cylinder head from the engine inside the car, hoping it could be solved easily with a replacement cylinder head, I was wrong again!

The removal made it clear, small alloy particles on top of the valve seats kept the valves from closing properly. But that was not the biggest problem, around the valve seats complete breaches had been beaten in aluminum, probably because of a neglected blown head gasket problem.

After seeing this I decided to remove the complete engine to do a complete checkup of its condition. That was a good decision! After a complete strip down of the engine, I inspected the cylinder bores. It is well known that the straight six has some cooling problems, causing cylinder head gaskets to be blown. And this problem mainly occurs between nr 5 and 6 cylinder bore. Although not really proven, I feel the waterways are simply too narrow.

Anyway, because of the cylinder head problems I was interested to see the cylinder bores. The alloy particles must have gone somewhere, and maybe even damage other parts as well. An inspection with a lamp made it clear, indeed nr. 5 and 6 where the troublemakers.

Almost halfway down in cylinder bore nr. 6, there was a huge gap inside the bore. As if some of the piston rings has forced their way into the iron. I never really found where this came from or what caused this. But with this knowledge, the engine was worthless.

Lucky for me, I had bought another spare engine, so I started stripping the engine and maybe I could build a good one out of two. I was not keen on simply swap the spare engine and drop it in. Since I had seen the damage a neglected head gasket could do to an engine I wanted to be 100% sure. The car will be a daily driver, and I didn’t want to swap the engines after 5 months time.

But an inspection of this cylinder head showed the same problems, although less dramatically around the valve seats. The cylinder block was, however, in good condition. The only thing needed was to finding a good cylinder head. Rimmer Bros where offering cylinder heads at that time for £150. Some friends in Holland even offered me complete engines for free. After a search around the Internet, and e-mail contact with several people I decided to drive to a friend in Luxembourg who had several 2.6 cylinder heads for sale, he allowed me to pick out a good one. Together with the spare cylinder block I could start the rebuild of my engine.

With the complete stripped down engine I drove to an engineering shop to ask for some prices and technical info. The advice was to get the cylinder block rebored to +0.10 mm, use oversize pistons, put in new bearing, and polish the cylinder head. The rest of the rebuild was up to me. They offered to do it at extra costs, but I decided to do it myself. (After all it is a hobby!) There was no work needed to the crankshaft at the time, so I left that out.

The crankshaft was in a perfect condition; with new bearings placed it was ready to refit the pistons.

When the engine block and cylinder head returned it was time to get to work. First of all I wanted to refit the valves into the cylinder head again. From the bunch of valves I had from stripping 3 cylinder heads I picked the best. I used the lathe to clean them and to see if they where not bent. I cleaned them further in an old stew pan using soda. If you let the water with soda boil slowly the built up carbon will come away rather easy. With a sponge you can remove the last pieces of carbon. Then it is time to do the grinding job.

With the cylinder head supported on wooden blocks, you start with nr. 1 valve. A trace of medium grinding paste smeared on the valve seat and with a suction grinder tool applied to the valve head you can start the job. With a rotating motion you grind the valve head to its seat, lifting the valve occasionally to re-distribute the grinding paste. When the valve seat is dull matt finish and there is no pitting visible, you can wipe off the paste and repeat the process with the fine grade grinding paste, similar to before. When a smooth unbroken ring of light grey matt finish is produced on both valve and valve seat faces the grinding operation is completed. Remove the grinding paste with a paraffin soaked rag and clean the valve seat and the valve. Be sure to also clean the valve stem and guide. Keep the valve with that particular location and start doing valve seat nr. 2 until all of the inlet and exhaust valves are grinded. Then it is time to refit the valves.

If you want to re-use the valves and springs, first carefully inspect the valve springs for cracks, or signs of wear. In my case I had so many spare ones, I could easily pick the good ones.
There is no need to mention that I did check the valve guides before I did the machining job. With a new valve inserted into the valve guide, the movement across the valve seat may not exceed the 0.508 mm (0.020 inch). If it does, the guide must be renewed. But the engineering specialist told me they where in good condition, and re-useable.

First drag a clean rag through each of the valve guides and do them one at the time. After oiling the stems and guides refit the valve into the correct position. On top of the valve stem an oil seal is fitted followed by the valve spring. Turn the cylinder head on its side and use a valve spring compressor to refit the valve springs, and fit the Colette’s that are used to keep the spring in place. Release the valve spring compressor and your valve can’t go anywhere!
The exhaust valves using double springs, oil seals may not have been fitted to later series engines. A friend of mine who did a rebuild job on his 85 series 2600 left these out but he complained that the engine was smoking at cold start probably because of this. I would recommend always fitting them, even if they were not required.

When all valve springs are mounted, check with a lamp to see if all the valves are closing properly, holding the lamp close to the vales and check for light coming from the inlet or exhaust ports. You should do this before you are starting to refit the valve springs, and you can also see if the valve or the spring is nicely round and not oval simply by turning them.