Anyone have experience with how many miles one could expect to get out of a 250 before needing a valve job? My '74 was apparently just before unleaded gas so I do use the lead substitute to help reduce wear. Currently I have about 44k miles on the car.
In leaded gas days, most engines ran over 100K before needing valve work. By 125K mi 99% needed total rebuild. I've never done a valve job unless there were actual problems. In other words, I ain't fixin' it till it's broke. If head(s) were off for other reason, definitely have one performed. My Fairlane had a valve job at around 43K, but motor was apart for replacing leaking seals & gaskets. That job cost previous owner around $1500. The Cobra has had two valve jobs, both times for burned valves.
I would be concerned with the valve seals. They get old and hard....then crumble and fall apart. This causes the car to use oil.
44 K miles is all about variables : regular oil changes ? - any time sitting in weather ? - Grandma or teen driver' ? etc. any smoke or major ticking and it's worth pulling head. If it's a knock or leaky rear main - drive until it dies ... IF you can find a machine shop willing, head refurb / 'valve job' can add reliable 'fuel management' and seal up combustion chambers with guide replace or knurl, spring/viton seals and back-cut valves or more esoteric work .... With head off measure combustion chambers to target compression ratio with any head milling. My '74 Maverick showed signs of sun damage in one direction , dry faded plastic and seatbelt on one side. 250 Engine ran but smoked at start and the Toploader 3OTT argued with shifts. 'breadboarding' a turbo setup proved too much for the tired 250 and lost the piston rings at @ 15 lbs boost. . . $ 300 low miles 250 swap from Granada ran excellent after performance' "Valve Job" and ARP fasteners, custom pushrods etc... added a supercharger, T5, 3.80 gears, suspension and modern boost / fuel / timing management for reliable performance and optimized drivablity Maverick Six' , hav e fun
True, still lasted in most all engines till around 75K, result of heat and chemical reaction on rubber. No doubt time plays a factor as well, still if it isn't using oil, I would not be worrying. In V8 engines, valve cover that has PCV valve will be far worse than oil filler side. The blowby contamination is pulled into PCV valve. When failed badly, engine will be lucky to get 300 mi to quart, I've seen as bad as 200 mi quart.
Do you think that lead substitute additive does any good ? I have also been using that High Mileage motor oil, not because of the mileage but just because it is nearly 50 years old now.
Ain't gonna hurt, though some additives will cause deposits on spark plugs. Of course lead did as well, why it was recommended to replace plugs at 10-12K intervals. High mileage oil will help keep seals pliable, stopped a small rear main leak on my 428. That thing had dripped for 35+ years.
Ford was putting hardened valve seats in heads by 1972 in anticipation of unleaded gas by 1975. I agree that if the heads are off anyway, a valve job is a good idea. At the very least, I would replace the valve seals, which can be done without removing the heads...
