NELSON BOHNALITE.

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Moving up my connecting rods to the piston end, I was inspecting the 2 sets of pistons I have, one from a small plug ’35 which should be a 385 CID and one from my ’33 366 CID.

Both pistons measure 3.485″ across the pin (I used darn near calipers instead of breaking out the mics). Both seem to be the same overall and compression height and are marked NELSON BOHNALITE.

Since they are not over sized, is Nelson the OEM supplier?

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Well I answered my own question

From Wikipedia

Nelson-Bohnalite was the name of a piston developed by Adolph Lincoln Nelson in the 1930s and 1940s. The pistons were licensed to Bohn Aluminum and sold to all the major auto manufacturers at the time. These were some of the first pistons to use an aluminum body with a steel strut, allowing for the weight of aluminum and the strength of steel where the piston moves on the piston rod. Many then existing brands of autos used this type of piston in the mid-1930s: Auburn, Graham, Hupmobile, Nash, Packard, Pierce-Arrow and Studebaker. (from Motors Handbook, 14th edition, 1937)

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And another

http://theoldmotor.com/?p=67095

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Bill, you are indeed a unique talent-ask a question on the board and populate the string with interesting responses too!

These style pistons, either original, NOS or new would be my preference in a rebuild.

John

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Yes, the steel strut is actually invar which is an expensive alloy that has the unusual quality of having zero expansion with temperature that keeps the aluminum the piston from growing in the bore when it gets hot – needed to allow the really tight piston clearance. It also was tin plated as an anti-seizure measure. they are more sophisticated than the lumps of aluminum you might get aftermarket.

Jim

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James I agree, many aftermarket pistons can be twice as heavy with lots of material around the wrist pin to make up strength for the missing strut. They require extra piston to bore clearance and often rattle on start up.

When I read an add that says ‘rebuilt’ engine, I usually don’t take comfort.

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John,

I posted before googling as I was sure I would only get the President of South Africa, an American singer named Ricky or a Brazilian Formula 1 driver. And Bohnalite?? I will try and reframe from answering my own questions in the future. Merry Christmas and Happy Hannukkah.

Bill

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James,

I think Invar is a trade name for Unobtainium.

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INVAR , KNOWN AS 64FENi. As a steel guy, that is pretty exotic stuff.

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Bill, don’t take my post as a need to refrain or reframe. I appreciate your contributions whatever format.

Best Wishes to you this holiday season!

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By most standards my ’35 should have been rebored, but it hsd NOS Bohnalite in very good shape, so I am gambling on original type pistons with a somewhat iffy original bore honed only but with the best oil control ring stack I could get. I could have had the thing bored and sleeved to keep the standard bore pistons, but sleeving isn’t without risk either, besides being expensive.

The main issue with a worn piston is the top groove is worn. In the past, instead of just automatically tossing old pistons and replacing, simple hand tools were available to cut the groove oversize and insert a steel “top groove spacer””. A piston will actually last longer with the top groove spacer than original (because the steel wears longer than aluminum). I think you can still get top groove spacers.

JIm”

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That is what I did a few years ago. My top ring groves on my ’29 eight were wallowed out. So I chucked the pistons in the lathe and cut the top ring grove wider so that I could insert a thin oil ring grove spacer ring. Then I lightly honed the bores to de-glaze them and used new rings. I have been running with this set up for quite a few miles with no issues.

Back in the day as a teenager (in the 60’s) when someone could not afford a complete rebuild and if the cylinder taper was not too bad we would de-glaze the cylinder walls and get the used piston thrust surfaces knurled. That would take up the excessive piston to cylinder wall clearance. Then with the new rings the owner would get many more miles out of the vehicle.

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Those old piston knurling tools are out there and are great if the bore doesn’t a have significant taper-if it’s around .005 your will wear out rings quickly.

Reworking the top ring groove and adding a spacer as you gents describe is good stuff too.

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The factory pistons are prone to failure and should not be run if it can be helped. Yes, I have reused them in the past. They are suffering higher failure rates as the years go by. Modern pistons with modern ring packages offer much better sealing and oil control with half the friction of the factory design. Aires or Ross are the go to piston, Egge pistons are still failing. If you have any questions about Egge pistons stop by the shop, we have several distroyed engines for you to look at. As do the Cadillac and Packard guys. Last month I was looking at a five year old Packard motor with an exploded Egge piston. But hey! They ARE cheaper! Both in cost and quaility. You get what you pay for.

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Happy holidays to my good friend in MA!-please share my wishes w/ John too!

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