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I have finally started to tear my 3TC apart to refresh the engine before it goes back into my 1966 MG Midget. I was surprised at how clean the inside of the engine was for an engine with 249,000 miles on it. The pistons all have .050 stamped on the top which led me to believe that the engine at some point in time was bored out .050 over stock. I measured the cylinders and they were all 3.368 which I believe is .020 over stock. No scoring in the cylinders and no ridge at the top of the cylinder. Checked one rod journal so far. It mic'd at 1.888 which I believe is stock size. So far so good.

Now for the mystery. The intake valve lifters for the #1 &#2 cylinders have been hitting the bottom of the cylinder head. We are not talking about a little nick. The is about 1/8" deep gouge in the cylinder head that perfectly fits the valve lifter. Rough measurement indicates that there is around 3/8" clearance at the top of the lifter travel between the lifter and cylinder head. Any ideas on what is causing this to happen?

Failed valve spring? That could have allowed the lifter to come too far up. No doing pressure to push back on the rocker, pushrod and then lifter. That’s my initial thought anyway
I’m assuming you measured and those two lifters are not magically way longer than the others?

The lifters are all the same length. I talked to Randy at BRD and he had never seen a lifter hit the bottom of the head in the 40 years that he has been messing with these engines. I was able to find a set of new valve springs and as soon as the spring compressor I just bought gets here I will replace the springs. Next up is to make some plugs to plug the smog ports. I am coming up with 16.5 mm x 1.5mm thread x 18.5 mm long.