Just curious. My 72 has a 350 in it with 125k that I am fairly certain has not been rebuilt. How long can this motors hold up? No smoke when it runs. Motor is quiet as can be when it is running.
I don’t see why 200,000 or better isn’t achievable. A fresh front cam bearing would probably help once you see a low hot oil pressure.
2 many variables like driving habits, terrain, cars transmission, gas and oil you use, type of driving u do. But my vote is forever
Also make sure the original timing chain and gears are replaced. The factory used a nylon coated cam gear to keep it quiet but after time it dry rots and falls off into the oil pan that can plug your oil pump pickup screen! With that changed and with it well maintained with the correct oil additives for older engines there's no reason you can't get 200K + miles out of it. Or until you want more power!
AND, IF you replace the timing chain & gears don't forget to drop the pan & clean out the debris that gets sucked into the oil pick-up screen. You may have good oil pressure but NOT the needed volume to keep things cool & lubricated. Tom T.
It's not just the plastic off the timing chain clogging up the oil pickup tube, but also with the plastic missing from the timing gear, it's easier for the chain to jump a tooth or two, and then you find out what an interference motor really means. Been there, done that.
Mine has 135000 on the clock was beaten close to death by the previous owner and still runs. Smokes once in a while on first start up & uses some oil but still takes the abuse. Did replace timing chain and rebuilt oil pump. Still have 12 psi at hot idle. Instead of replacing the front cam bearing I’m working on rebuilding a block I picked up.
Keep the oil decent and the carb in tune. A dripping carb will wash the cylinders down and it will burn oil. It won't run forever but if your proactive it should go a long time.
Doesn't it depend on your cam? I thought any engine could become an interference engine if the cam opens the valves high enough to contact the pistons at any point during rotation?
This. I had my timing chain gear plastic teeth break off and my timing chain jumped a few teeth on my 66 300 years ago. The 350 is the same. Once the chain jumped a few teeth, the valves "tapped" the tops of the pistons. Interference motor. If you still have the original timing chain gear, even if it's a low mileage motor, it's still 40 to 50 years old now. The plastic gets brittle and will break off. It's not a matter of if, it's when. It's cheap insurance. The replacements are steel. You will never have to worry about it again. Just don't forget to put the oil slinger back on. Lol. There are engines out there that are non-interference motors, meaning the valves can never contact the pistons. I can't give any examples, but they are out there. Non-Buick.
My father's '76 350 4bbl in a Skylark S/R was still going fine at around 285k miles; but it struggled to rev beyond about 4000 rpm. It was untouched and very well maintained.
143000 miles on my '72 GS 350. Engine overhauled at ~~96000 miles in the late 1990's. However, I changed the timing chain & crank gear & plastic cam gear in 2001 with 113000 miles because I saw the plastic gear. last year, I replace head gaskets & rear main seal with engine out of car. Take care & perform regular maintenance, and these engines will last. Also, don't beat the crap out of them.
My Father in Law had a 76 Delta 88 (Olds 350) that he bought new and ran to 425K with the original drive train, sold it for $100 in the early 90's to neighbor kid and it still ran for a few years after that.
Those engines were designed to run on low lead fuel. Without it, your valves will lose perfect seal around 100k and to keep performance up to snuff, you should do a valve job, along with timing chain/ gearset. It'll run till it pukes without some attention.
