D. A Look Inside The Big Block
Post date: Jul 20, 2015 5:45:8 PM
As expected, the engine was in need of some attention. You never know what you will find when you take a motor apart and this one had no real surprises. As we were made aware, it had been rebuilt at least once before as the block showed signs of decking, Typically when a block is decked, it is also bored, etc. In fact this was bored .030" over and the crank cut .010". With the heads off you can see two things immediately - it was using a good bit of oil (deposits on the piston tops) and it was running lean (white exhaust valve pockets although the heads are not pictured here).
Once the pistons were pulled out it was clear that the rings had never properly seated. There was no ridge in the bores whatsoever and you could still see the cross hatching from the honing, it was just glazed-over. There was some very minor scuffing in 3 or the bores, but nothing significant.
The rod bearings told a bit of a different story. Clearly this engine had been run low on oil - probably because it was leaking / consuming much of it. This kind of bearing "report card" isn't one to be proud of!
The cam bearings looked fine so the block, crank and rods we all inspected and mic'd to see what was and wasn't in tolerance. With everything cleaned up, remarkably everything was in spec (block bored .030" over and the crank mains and rod journals .010" under), so the only block work required was a good cleaning. The pistons also showed very well with no scuffing of the skirts. So it will be new rings, bearings, cam and a 3 angle valve job and the motor can go back together.