The Imperial: The Accidental Stopping Point

The progress in building the Chrysler LA 360 cubic inch (5.9L) small block V8 has been going well. New bearings are in, the crankshaft and camshaft went in without a fight, and it was time to put in the pistons. Except, last time I popped in here, the rings on the first piston I had picked up pretty much fell out, broken. Time for new rings! Honestly, it's cheap insurance for your new engine and a great excuse to clean out decades of carbon buildup from out of your ring lands. Using a shard of broken piston ring that I'd ground the ends down on to make a kind of knife, I laid my tools, degreaser and pistons out onto the trunklid of the cheap Cadillac limo in my driveway and got to work.

This is a great conversation starter with your neighbors. Always starts the same, though: "What the hell are you doing now?!"

This is a great conversation starter with your neighbors. Always starts the same, though: "What the hell are you doing now?!"

After spending most of an afternoon chipping away at overcooked dead dinosaur leftovers, it was time to get the rings onto the pistons and the assemblies into the block. And that went just fine, up until I got to the very last piston to install. On a small Chrysler V8, the pistons are ordered as such:

#2 piston was the last one to go into the block and...it didn't. Not even a little bit. It hung up from the moment the piston skirt dipped into the cylinder and wouldn't budge. While my initial reaction was to get an 8-pound sledgehammer and prove that man triumphs over machine, nobody wins in that regard, so the piston came out and an investigation was launched.

Things known before the investigation started: this is a .040-inch overbored block and that work was done before my hands ever touched the engine. The pistons were numbered before removal and have been numbered all the way up until this point. There is no reason to doubt that the piston marked #2 is as claimed. And a quick test of placing the piston into the bore top-end-first proved that overall, the piston has the right diameter...only the piston skirt is the problem. And the lookover of the piston proved that theory...

Just a little will do 'ya.

Just a little will do 'ya.

Bad photo, I know but look right at the center of the skirt. Just off to the left of center you can see an obvious chip where the connecting rod had a less-than-gentle meeting with the skirt. This, in turn, pushed the piston out a thousandth or so into bad territory, but only on one small spot. So, what to do in this situation? The options included ripping everything out of the block, getting the bores micrometer-measured and ordering up a set of custom pistons and what I ended up choosing because I have a budget measured in the tens of dollars:

Yep, this happened.

Yep, this happened.

Every machinist and engine builder might cringe, but that budget deal isn't a joke in my world. Once the high spot was located and isolated, the sandpaper was broken out and used. 180 grit cut down the high spot, 380 grit was used for cleanup work and 800 grit polished up the surface. Moving a little at a time, and checking fit and measuring with a caliper, we got #2 down to where the calipers were happy and the piston felt perfectly natural in the bore. If I had money, I'd have just sprung for new slugs and if this was anything more than just an engine for a street driven car, I'd be more concerned about this move, but as it sits...I'm good with this bit of shop hackery.

Bonus surprise: The correct displacement for a .040-over Chrysler 360 is 367 cubic inches. Nice.

Bonus surprise: The correct displacement for a .040-over Chrysler 360 is 367 cubic inches. Nice.

Until next time...