Engine life

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The thread on the 1935 845 Pierce-Arrow digressed to the topic of how long they might last. Of course there is a great variability depending on which component is being discussed. In terms of the engines of that era, the plain cast iron rings were considered normal wear items and expected to be replaced at about 15-20000 miles and put into the original bores and pistons. The head was “de-carbonized” at the same time. The piston would likely show excessive wear in the top ring groove at the second or third ring job. The original piston could be repaired with a steel “top groove spacer” after being cut by a hand tool designed for the purpose. After the top groove spacer was installed the top groove would last longer than it had originally. Engines could be re-ringed successfully with cylinder bores tapered as much as .010 – .012, but the new ring’s life was shortened significantly with more taper and the oil consumption would be higher than original.

In that era oil consumption was measured in terms of gallons/mile. A prolific Studebaker engineer named Stanwood W. Sparrow stated in 1935: “…the oil economy frequently fell short of demands of a public that demands 500 miles/gallon at any speed and better than 1000 miles/gallon at speeds below 50 mph”. That’s 125 to 250 miles/quart when they were new. A large factor in reducing oil consumption after WWII was the chrome faced 3 segment oil ring. Besides lasting a lot longer its biggest advantage was cutting the tendency for oil to be pulled up past the rings at low throttle and high inlet suction – hence the cloud of blue smoke at idle or after coming down a hill.

The biggest factors in the shorter life of piston rings and top grooves was the lack of effective air filtration allowing abrasive dust particles in and the limited wear resistance of cast iron rings. Dramatic improvements to ring life happened with chrome faced top compression rings after WWII and pleated paper air filters in the 1950’s.

A pre-war engine rebuilt with Post WWII rings and modestly worn bores can attain oil consumption much less than when new – and reduce smoke and engine wear at the same time, i.e. retaining more of that original cast iron in the engine.

I re-ringed my modern ’66 Chrysler with .006-.007 taper in 1998, it has run well ever since with good oil consumption (except unrelated vapor-lock and bad condenser issues). If there had been some belief that the engine would ever see another 100,000 miles perhaps I would have had it bored and replaced the original pistons. As it was, the block never saw the inside of a machine shop.

Suppliers of antique engine parts invariably supply original style cast iron compression and oil rings automatically. There is little risk of argument for them about suitability or break-in, but if the engine was rebuilt authentically with these rings and original air filter I wouldn’t expect more than 15-20000 miles before lots of smoke.

Now that I have outed myself as one of those uncouth old school restorers who will never take the field at Pebble, let me add that it seems the goal of many restorations is to rebuild their engine at high cost in anticipation of future generations driving them until the end of time. Given I probably drive my ’36 Packard many more miles – no trailer – than the majority of pe-war collectors and have put 25000 miles on it in 30 years, I don’t view this as a very pragmatic goal.

Jim

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Very realistic appraisal I think. I am rebuilding the engine in the ‘31 because I want a reliable driver. It had two different-design pistons and cracked Babbitt it the two rods I looked at, and obvious crank journal wear. I seriously doubt it will ever see enough use to wear out; rather it will be subject to deterioration due to sitting unused and due to time.

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I’m with Jim on this.

While if an engine is in terrible shape, it needs to be bored, crank ground, etc etc.

BUT if an engine is running, doesn’t have horrendous taper in the cylinder bores, does not have rough, scored or gouged crankshaft journals, and does not have cracks in the block, then it can be greatly improved and given a new lease-on-life with a careful ‘in-chassis’ overhaul.

I see no reason to rebuild an engine as if it is a workhorse engine and expected and needed to work hard for 100’s of thousands of miles. The Pierce engines will run a very, very long time with not-so-perfect rings/bores/loose pistons. And the size and area of the main and rod bearings, along with the low rpm engine design, allows a person to polish the rod journals, and have the connecting rods rebabbited, And hand-fit and scrape the babbitt to fit the journals. This is much faster than removing and replacing the entire engine from the car.

i have been amazed at just how BAD an engine can be, and not make noises, not smoke terribly, and not use horrendous amounts of oil.. And, as Jim mentioned above, oil is a consumed item in old engines.. They were designed that way. In some engines, the only oil that gets to the exhaust valve stems to lubricate them comes from the unburnt oil from the combustion chamber.

As Jim mentioned, a good air cleaner, and oil filter goes a very long way to extending the life of our engines.

Greg Long

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You’ve got to love Marvel Mystery Oil, a brand approaching 100 years old,

for lubricating those hard to reach spaces that are getting starved due to

our penchant for rebuilding old engines tight and with modern parts.

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