GT380 Headache

The 1975 GT380 rebuild story continues. Looking at the old cylinder head gaskets, it was obvious the centre one had blown, and had been run that way for a while. I’ve included a photo to the left. The mating surface on the barrel was cut as could be seen using a machinist’s square. As I had to repair what looked like cold chisel gouges in the aluminium anyway, I also filled the cut marks and then lapped the head on a flat surface (I’ve included photos of the repair etc. below). I used JB Weld for the repair and have had good success with this in the past for similar repairs. 👍

The GT380 uses a one piece cylinder head, but has three separate barrels, and when I had the barrels fitted and torqued down I found that with the left and right cylinder head bolts in place, the centre cylinder had an 8 thou gap between the head and the barrel. I could torque the head down in the centre and reduce the gap but I wasn’t happy doing so as obviously this was flexing the head (which by the way was flat). This gap is most probably what caused the original damage and the blow out of the original head gasket and having just repaired the centre barrel I didn’t fancy ruining it a second time. So after thinking about it for a bit, I just cut the cylinder head into three pieces and my clearance problem was solved ! 👍

With the three cylinder head pieces fitted in place, and as the mounting points for the RAM AIR cylinder head shrouds are on the left and right heads, everything still fits, and looks no different than before. And while I suppose it is possible the harmonics may now be different (less cylinder head dampening) I know that at least a few other owners have also gone this route with seemingly no ill effects, so I’m not too concerned.

The build continues ! 😎

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