My 2 cents thats alot of miles on a motor.I had a engine rebuilt about 5 years ago.I thought it ran strong but burned just a little oil and the motor was not near 200k miles.This engine was in the car when i bought the car.Yeah, I adjust them at least once a year. this motor has 343,000 miles on it - but always ran very strong till recently. Oil changes are at 2,500 + with a new Wix finter every time.
Some days - it drives great, then like today-- it's sputtering & backfiring out the exaust. Not too long ago the battery was dead. It charged up fine in 1 hr. Sometimes lights get real bright & then dim. Maybe a Voltage Regulator ?
After the rebuild with stock parts it was a night and day difference.
No matter how often you have changed the oil parts will ware.All the miles on that engine if I were in your shoes I'd have it rebuilt.Start yourself off with a fresh engine.
I had a short block small block 350 rebuilt for $650.00 2 weeks ago with upgrades.If you must,save up and get a fresh engine in your ride.All those miles once you cure this prob your having it wont be long for another.Over 300k thats alot miles man on a motor.Now just me I didnt hit 100k miles in 7 years on the engine I had rebuilt so just think about the ware and tare on the motor you have.
My short block was rebuilt due to I mounted some edlebrock performer heads.Once them stock heads came off I didnt like the way my cylinders looked.But yet and all I thought my short block was healthy and the engine ran great to my knowledge.Had waves in the bores due to my wife overheated the car and still drove it.
Not being a phuckstick just my 2 cents on this thread.