engine power decresing over the years, how much?

[CB]

I was wondering if you are a 2nd or 3rd (or X) owner of a car with a let's say stock 1968-1970 383 cui engine.
No one has done anything to it, besides maybe install another carb or headers.
I was wondering how much HP would be left in an 40+ year old big block.
And where the biggest 'power drain' occurs over time. (worn valves?)

[Ghoste]

I would think worn rings and cylinders?

[myk]

Too many variables to consider.  The motor in question could have sat like a stone for 40 years, in which case it's completely worthless despite having low hours of operation; or someone's grandma could have been driving it daily for the past 40 years with trips to the grocery store and bridge club, which would probably leave the motor in decent shape...

[Challenger340]

Valve wear is a big one...Valve Seat Recession which if the Valve sinks .050" from new means you can minus that much off the Cam lift because the valve has to climb that much higher off the seat to start actually flowing air ?....usually a burnt Valve or two...pretty obvious by the chugga-chugga rough idle, and easily verified with a Compression test.

Cylinders glaze and Rings wear over time....also results in power loss, also easily found by a Compression "Wet & Dry" test to verify....or by simply removing the Breather on 1 V/Cover side, while leaving the PCV "IN" on the other(should be minimal Blow-by coming out the Breather with the PCV "IN")
Cam Lobe wear nowadays for the ones still running ?

But really, with these old Engines, no way to tell an Engine's condition "strictly" by mileage, always exceptions ?
It all depends upon "how" they were driven, and "MAINTAINED" over the years/decades.

Mine is an original, "untouched", as in never rebuilt or out of the Car, 375hp 440 Magnum in a '69 R/T Charger with 130K showing.
It was meticulously maintained, never beaten of bagged upon....without being well warmed up, and pretty much always in "D" left to do it's thing on the rare occasions it was tasked.
It even still has the original Points & Condensor Ignition in it !
It can still Boil the tires at will through a 3.23 Suregrip Diffy with a stock 727 Auto, chirps into 2nd, or, will actually leave another 5ft strips of black on a good day....blows no Oil blue smoke, and "goes" really well..."surprisingly" well in fact.
and,
I have seen other Engines decades ago(I am an Old Guy)...that were BAGGED on...beat like a red-headed stepchild...with little maintenance.....that were literally sacked out at 80K.
Just all depends on the particular Engine.

[CB]

thanks for the good info.
I am close to get the '72 running again but I don't know what to expect.