Saturday, 12 February 2011

New Sprint engine (part 1)

As I will be visiting an old school engine builder shortly to see what flowing and porting can be done to a Sprint head, I decided to start the engine rebuild in earnest. Although I do have a bare spare head lying around I thought it a good idea to dismantle the complete Sprint engine that has been lying around for quite some time now. This engine actually is my part of a complete Dolly Sprint René and I bought a few years ago for a few hundred Euros;

After we got that car back home it was completely dismantled and everything that was useful was stored, the rest was binned. The engine went into a large crate, where it lingered till today. After a bit of struggle (involving recovering a Nissan from a soggy lawn with the little Landy) we managed to get the crate out of the shed and the engine out of the crate;

A quick inspection learned that, although rather oil stained, the engine looked remarkable original and unmolested, a promising start. First thing to do was put some containers underneath the engine and get rid of the oil and remaining coolant. While these were draining of, I first looked for the engine number which I found were it should be;

After that I removed the spark plugs. Turned out that the previous owner had over tightened them. Took quite some persuasion to get them out, not helped by the fact that my normal Sprint spark plug socket has only a rather short cross bar. Luckily I found a slightly longer bar that fitted, and this gave just enough extra leverage to get the plugs out. With the plugs removed looks like this engine had been running a bit rich, but nothing alarming;

The score so far being 4 over tightened spark plugs, incorrect carburettor set up. And did I mention the fact that the spark plugs were completely drowned in engine oil?
After that I started with removing everything on the outside of the engine, like manifolds, oil pump (one bolt missing), cam cover, clutch and flywheel, water pump (with a lump of lead wedge inside the block), sump (without hidden treasures) etcetera. Of course Murphy had to prove a point again. The most inaccessible bolt from the inlet manifold put up a fight;

Which it lost in the end! I ignored the thermostat cover bolt that sheared of as I won’t need the manifold anyway. And while removing the cam cover I was reminded of the fact that I removed the rockers a few years ago when I had a slight problem with the cam shaft of ‘t Kreng. Plan was to have them refaced, but I never got round to that, wonder where I stored them!? The rest underneath the cam cover looked quite reasonable indeed;

Which could also be said of the bottom end. Which was revealed after removing the sump, also no obvious faults;

With the sump and oil pick up removed it was time to put the engine on the workbench and have a go at the head. I did have some worries here, because the ”normal” 8 valve variant of Triumph’s Slant Four engine has a bit a reputation for seized head studs. But contrary to the 8 valve engine, were the head bolts and studs sit out in the open, on the Sprint the bolts and studs sit inside the head under the cam cover, where they are constantly sprayed with oil. As a result of which removing the head was very straightforward. One stud could even be removed with a screw driver;

The rest came out very easily after I locked two nuts together;

With all the bolts and studs removed, all that was needed was a modest blow with a rubber mallet to free the cylinder head from the block. As you can see the internals of the head look pretty much OK, with no visible pitting or oxidation anywhere, which is very good news indeed;

Next came the distribution, although the hydraulic tensioner was out a bit, there was hardly any wear on the tensioner’s face or in the chain itself. The same could be said of the two chain guides. The only signs of wear if you can call it that was an imprint of the chain on the guides surfaces were the chain had rested for an unknown amount of years;

Remained the bottom end and the pistons. This job also went pretty smoothly, but the most pleasing was the fact that the internals of the engine are in pretty good condition. All bearings look like they are new;

The pistons turned out to be original specification Mahle and in pretty good condition too!

And the cylinder walls still have clear traces of honing on them. All in all it looks a promising base to use as new engine for the new Kreng. But the engine block and crankshaft will be a matter of comparing it to the other TR7 engines I have lying around. One of which is a low mileage, low compression FI engine ...

To be continued ...

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