1977 GT500 – Engine Issues

So the time had come to take a closer look at the two GT500 engines I had  – one is a 1976 and the other a late 1977. I scraped the worst of the accumulated grime from them but did not bother to do a real cleaning as the plan is to do a full strip and then clean and rebuild.

The first issue was the clutch side cover on the 1976 engine didn’t want to come off – and it took me a few minutes to realise that the reason for this was the shifter arm had been welded to the shifter shaft !!! I have to admit, I hadn’t seen that particular bodge before, and it didn’t bode well for the condition of the rest of the engine.

After a few minutes of grinding, that was sorted and it was time to pull the heads off and take a look at how bad the barrels and pistons were. Thankfully, the 1976 engine actually seemed to be in pretty good shape – the barrels were still on there original bore and there were no obvious signs of oil starvation, the crankshaft felt good and there were no signs of excessive play in the con-rods and small and big ends. There were signs that the chain had come off at some point as there was obvious damage to the lower engine case, but that was possibly repairable if I had to. The 1977 engine was a different story.

When I pulled the heads on the 1977 engine. I was quite surprised to find that one barrel was at second over, and the other was still on standard bore ! As well, there were obvious signs of fairly serious engine damage in the past as the left cylinder head had a deep gouge in it – and then most surprising of all, it appears the right cylinder head  is actually cracked the width of the cylinder right through the spark plug hole so both of them are pretty much scrap. The barrels also have been played with – the intakes have both been opened up, probably to try and make the engine breathe a bit better, and the liner on the cylinder that has been bored to second over is cracked in the area of the intake transfer ports. The crankshaft seems OK as well as the con-rods and the small and big ends, but the engine must have been really unbalanced with having the cylinders unmatched and probably buzzed like crazy at speed. We’ll see if the crank is damaged once I get it out completely next week.

The good news out of this at least is that I do have one set of barrels and heads which do seem OK, and I also have four con-rods which seem to be in good shape which is very nice as these specific ones have not been available anywhere for years now.  The crankshaft bearings likewise pretty much are not available – you can have them made at considerable cost – so it was very nice to find that, at first glance at least, the original bearings may be salvageable.

I’m hopeful the transmissions will be in better shape, but of course we will know soon enough !

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