Repairing the engine

Sorry I have somehow lost most of my engine photos!

The engine fitted to the Iron Maiden was a mighty Perkins 4-108 4-cylinder 1.8 litre diesel, producing 55 bhp and 83 lbf ft. In theory. In practice it produced 0 bhp due to being very badly broken.

The Perkins 4-108 engine, taken from the manual

John told me that he had sold the boat to another buyer a few weeks ago, but that the buyer had changed their mind and returned it. En route, they had managed to overheat the engine presumably through a water system failure.

Through ignorance or stupidity, they pressed on, getting hotter and hotter until the head gasket failed, spraying oil everywhere and starting a small fire on the exhaust manifold.

I was unable to find out whether the engine had actually seized, or whether the smoke from the burning oil had finally alerted the berk to what was happening so he could pull the stop. Either way, I wasn't too hopeful about what I would find inside.

The first thing I needed, after giving the engine and bilges a good clean-out, was a new head gasket.

This proved far more difficult that it ought to have been, mainly because the official supplier of Perkins parts. Diperk, are a bunch of morons. After banging my head against the Diperk brick wall for about three weeks, I found a small friendly company called Mead Plant who were able to send me a gasket the very next day. Still, Diperk were so unremittingly incompetent, that I did finally end up with a full gasket set I hadn't been charged for.

Note: Service Manual If anyone reading this has a Perkins 4-108, 4-107 or 4-99 engine and would like a copy of the service manual, I have it in PDF format, just email me for a copy.

The spanners come out

My engine compartment, after the repairs were complete and the bilges cleaned and painted.

Removing the cylinder head was not a particularly difficult job. All the bolts and pipes detached without breaking, there are no cam shafts to deal with and the whole thing has pretty decent access. After a few hours work, it was time to lift the head and see what lay beneath...

... Hmmm, not too bad. The cylinder bores showed little signs of wear (no lip near the top). Two of them had water sitting in them which had caused corrosion to the walls, but this cleaned off easily. I got the engine turning over by hand just fine, and had to cross my fingers that the rings would be OK.

Then I took a close look at the head itself and - shit! - it was cracked. A hairline fissure between the pre-combustion chambers and the exhaust valves on two cylinders.

I thought I might as well give it a go anyway, so I put everything back together, changed the oil, filters and cooling water, primed the fuel system and tried to start her up.

After much grinding, spluttering and foul smoke the engine finally fired up. Hurray! I hadn't expected it to run at all in that state, but it looked like there were no other serious problems, and no leaks from the head gasket either.

It could not be used like this though, as exhaust gasses were getting through the cracks into the water system. Big angry bubbles fought their way out of the header tank, causing overheating. Still, it could easily have been much worse. Tough old engines these.

As the head is cast iron and quite delicate at that point, the cracks were not repairable and I needed a replacement head.

The hunt for a new head

'Maiden' voyage in the rain

Buying a brand new head was out of the question due to cost and the fact I would have to get it from Diberk, so I started to hunt around. Within a week, a Perkins 4-107 head came up on ebay and I was thrashing all the way up to Scunthorpe to get it. The 4-107 is very similar to the 4-108 and has an identical head. Or so I thought.

For £150 I picked up a fairly battered old head from an ice-cream van, complete with valve gear, and as a bonus an unused set of 0.5mm oversize pistons and rings for a rainy day. Bargain.

My joy was short lived though, when I tried to drop the new head into place; the bolt holes are too small for the studs to pass through. Buggeration.

I took the head to the local specialists, Cambridge Rebores in Burwell (01638 743797), which I should have done in the first place. As soon as he saw it he asked if it was a 4-107 or a 4-108. I replied the former, "ah," he said, "the bolt holes are too small." I had come to the right place.

Passing through Bait's Bite lock

For £200, they resurfaced the head, replaced the valve seals and one valve, lapped the valves in, drilled out the bolt holes and some other bits and bobs. The head was as good as new.

It fitted, with a bit of persuasion from a mallet, and once again I put everything back together and refilled the water (9 gallons of it!). It started and ran!!

The time for the 'Maiden' voyage had arrived, and with my Dad's help we somehow reversed the boat out of the long muddy cut into the Great Ouse river, and started the long chug home.

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