gotta question for yall. Something just aint makin sense. Bought my 60 cad in 2000. Ran good, everything worked (xcept the antenna), drove it almost every day for 2 years. It slowly lost power, started smokin, burnin oil, etc. Finally, sucker started coughin white smoke, so figured it was a head gasket. WRONG. it had burnt two pistons, number 4 and number 5, and was soooooo bad they had shredded the rings, tore up the pistons themselves, and one of the pushrods had torn into the water jacket. What a fuggin mess. Engine shop said no prob, bore the cylinders, sleeve the bad one, and get back on my way. Installed hardened valve seats, blah blah, polished this, bored that, got it back together, and we still had a few prob's. Carb was crap, so I got one online. New carb was good lookin, but still ran like crap. Rebuilt NEW carb, found it full of polishing sand. SOB's. Anywho. Fixed that, and WOW did she run beautiful. Again, bout 2 years later, towed a big trailer from CHI town, to Wilm, NC. On the way, started losin some power, burnin a minute amount of oil, but puffin whitish smoke like nobodies business. Took it to a shop, found NO oil in the radiator fluid, no radiator fluid in the oil. Did a compression test, np. Did a leakdown test, and two cylinders were like CRAP. New shops solution was to rebuild it. I thought that was a crock, after 2 years, and kept driving the sucker. Figured I'd drive it till it Died. Well.. about another year later, it did. But it was the trans that quit first. So... found another 390 first. Pulled my 390, did the swap, still gotta get the "new" motor runnin right (need a starter, and to set the timing right). Anywho with my "extra time" I decided to rip apart my old 390 to see what the hell happened. Oil pan was full of metal pieces, rings, and other bigger stuff. So, pulled off oil pan, valve covers, intake, valves looked good, intake was good, so I pulled the heads off. Man there's the problem. I could see daylight through the sides of the pistons in the number 4 and 5 cylinder's again. They had shredded the rings, and once again ripped themselves up. So.. my question is... what the hell causes that? Intake and exhaust valves on the heads look great, no leaks I can see. Crankshaft and camshaft are clean, no sludge anywhere. Oil was constantly changed ( about once a month, every 500-600 miles). This sucker was CLEAN. Why did it fail again? Only thing I can think of was that the lined cylinder was outta round, or the rings were installed improperly. WTF?
I'll start by saying that I'm no expert... I've had my 60 cad for 26 years, and have owned others too. My problems with my 390 led me to getting a 472/400 combo for my 60 cad. I went through two rebuilds. My problem was rod bearings though. I rebuilt it cause it was smokin so bad a stoplights that we were killing mosquitos for miles. Then, after the rebuild, came the rod knock...rebuild...repeat. It was months between rebuilds as my wrench decided to become an outlaw bike club guy, so he had to schedule my work around stints in jail...then he became a rat, went in to witness protection etc...needless to say after it blew the second time I was on my own. Then a buddy calls me about this wrecked 68 cad that he had just rebuilt the motor on. The kid that wrecked the cad bought a 62 caddie later with a bad tranny. I traded him my old 4spd jetaway for that 472 and the 400 behind it. Took some carving to get it in, but I had Kiwi Kev to help. Don't miss the 390 or the leaky jetaway tranny. So you might say I've upgraded my 60 to 68 standards as far as a power plant. Modern guy eh? As far as what is happening to your motor? I think sometimes these blocks have problems that manifest themselves with time. Perhaps the water jacketing is corroding away? My 390 always had cooling problems. I always had a rebuilt water pump in my trunk waiting for whenever the one on the motor failed...which for some reason was often. I love the way those old motors looked, but I don't miss mine...except it might look nice in the roadster that I'm starting soon...oh well too late.
Sounds to me like an oiling problem.. plugged passages in the crank or a couple rods installed backwards, so the little end ain't getting enough splash to lube the pin, causing a binding wristpin and, hence, a scuffed/galled skirt. I've run a lot of early cad motors well past 100,000 miles without a rebuild and never had any kind of problems like you've had. Now 429's on the other hand are pieces of crap which are best used as a boat anchor (don't ask...). --Bob
ok.. here's the wierdest part. Pistons are tore up on those two cylinders, but the cylinder walls appear perfectly clean!!! I cleaned em up w/ carb cleaner (I had some on hand.. not a generally smart thing to do I know). I can still see the honing marks on all 8 cylinders, and I don't see any lengthwise scratches, except a little bit from what appears to be the rings on the two bad cylinders. But not anything near enough to cause the rings to fail or cylinders to tear up. Anybody think this could have been a timing thing? I'm wondering if some wierd way these two cylinders were firing at the wrong time? I know the firing order, and i know they were factory correct, but could it have somehow cought a linear spark from the wires being so closely tied together, and sparked at the wrong time? I dunno, graspin at straws here.
did the pistons of those cylinders look like they were running lean? 1. perhaps you had a pushrod or camlobe issues on those ports that caused valves to hang open. perhaps a warp on intake or other air leak? 2. perhaps an oiling issue, but you mentioned the cylinder bores looked clean? 3. distributor lobe out of whack? hmmmmmmmm... -scott noteboom
Connecting rods straight? I'd expect a bent rod to FUBAR the cylinder it's in, as well as the attached piston, but who knows. How much piston-to-cylinder-head clearance was there? Could the pistons have been smacking the head? Hope you solve the mystery.
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