May 20, 2015 – Engine Tear-down and Further Inspection
Tearing down an engine isn’t difficult, or particularly time consuming once you’ve done it before. Thanks to the Engine Overhaul class I took at McPherson, I’m pretty confident I can disassemble an engine without doing any damage. It’s the putting it back together where things can go wrong. I’d mostly torn down the Craigslist motor several months ago when I bought it, but due to a lack of space and the fear of losing things, I’d actually put it back together. I’d already inspected the Craigslist motor when I tore it down the last time, so I didn’t have any real measuring to do on that one.
The motor that came out of the car, however, needed to get the full treatment. Previously I’d only pulled one head and the oil pan. That had permitted me to get a broad view and had quickly told me what I’d feared: this engine has already been rebuilt once before. Given the quality of the decidedly mass-market rebuild, and based on what I’d found on that initial inspection, pulling both heads and measuring each bore was mandatory. Cheap rebuilds can include no-no’s like different sized bores on one bank or even different sized bores within the same bank. Apparently it’s not uncommon to see some bores .030 and others .040 within the same engine, possibly even some cylinders bored out .060 (a very risky endeavor for a 289) on really bad mass-market rebuilds. Different sized bores are bad for lots of reasons, not the least of which is that cylinders won’t see even compression. Other signs of a mass-market quickie job are mismatched connecting rods, which this block also had (rods and pistons should generally stay with the bore they came out of, both for inspection purposes and because they’re balanced to the crank). Any decent re-builder will stamp the bore number on the rods and caps before he or she pulls them out (the caps MUST stay with their rod because they mate together to form a perfect circle). While it appears the caps were kept with their matching rods, the numbers stamped on each set didn’t match the bore numbers.
Worse yet, when I re-measured the bores I found out I’d bungled the measurement the first time; this engine had been bored .030 over on all bores, not .020 as I’d originally thought. So this engine really only has one rebuild left in it, if that. After this discovery, I chatted with the previous owner who was still in contact through a friend with a family member of the owner before him. That contact filled in some of the details. Apparently the second owner had blown the engine at around 75,000 miles, so they had a shop put in a rebuilt motor. But the car was never really the same after that, and it kept fowling a spark plug, so after they got tired of changing the plugs, they parked it. Further, we also learned a bit about the previous body work. At some point after the car had been parked for a brief time, a member of the family backed into the left rear quarter panel, so they had that repaired and painted.
The outcome of this whole dis-assembly process, though, is that I’m probably better off trying to find a standard bore 289 or 302 core block and using that as my basis for the rebuild rather than rebuilding the blocks I have already. Back to Craigslist I go! Luckily I now have two rotating assemblies, so all I need is the block. We’ll see what comes up.