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Here are a couple of pictures of the pistons in a 1934 Hudson 254ci straight eight engine. Car has 46,xxx original miles. I have pulled the cylinder head, intake and exhaust manifold and water jacket cover, to clean out and inspect the engine.(more will be pulled apart) The question I have is on the stamping on top of what I think is the factory pistons. All pistons are numbered 1 thru 8, all pistons have 993 stamped in them, all pistons have 10 stamped on them, pistons 1-2-3-5-7-8 have the letter E stamped on them, pistons 4-6 have the letter D stamped on them. What do these mean? what is the difference in the E and D? 993? Does the 10, mean 10 over? 

engine and pistons 015.jpg

engine and pistons 016.jpg

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My guess is that the pistons are from a previous re-build, and the mechanic stamped their numbers in the piston crowns.  The pistons could be 10 over as you say and the ring end gap was set for each cylinder, hence the numbering.  As to the "E", "D" and "993", I don't have a clue.  Oh by the way, my two previous guesses were just this side of clueless, so don't spend too much time pondering them.

 

Cheers,

Grog

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14 minutes ago, capngrog said:

  Oh by the way, my two previous guesses were just this side of clueless, so don't spend too much time pondering them.

 

Cheers,

Grog

A person could apply that statement to a lot of things in this world. Made me laugh.:lol:

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The letters E and D could well refer to the fit. Bores were sometimes designated for minor differences in the final finished size, and matched with slightly different finished sized pistons. You may see corresponding letters stamped on the top surface of the block, by the cylinders. I have no knowledge of Hudsons, but have seen this on other engines, though which makes they were eludes me at the moment.

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info from Hudson Mechanical Procedure Manual:

Original size of cylinder block is stamped on lower face of Valve chamber. 

The size code letters and piston weight, in ounces and quarter ounces, stamped on the heads of the pistons.

In addition to to the size and weight marks all original pistons installations are numbered to indicate the cylinder block number and the number of the cylinder in which the piston is fitted.

 

Cylinder  size and code............................................Piston Code........................................Piston Ring size....................

(Stamped in valve chamber)-----------------------------------( top of piston )------------------------------------------

 

3.00----------------------A------------------------------------------------B---------------------------------------------------------3.000

3.05----------------------B------------------------------------------------B---------------------------------------------------------3.000

3.01----------------------C------------------------------------------------D---------------------------------------------------------3.000

3.0015------------------D------------------------------------------------D---------------------------------------------------------3.000

3.002--------------------E------------------------------------------------F----------------------------------------------------------3.000

3.0025--------------------------------------------------------------------F----------------------------------------------------------3.000

3.004----------------------------------------------------------------------J----------------------------------------------------------3.003

3.005----------------------------------------------------------------------L-----------------------------------------------------------3.005

3.010---------------------AO--------------------------------------------BO--------------------------------------------------------3.010

3.0105-------------------BO--------------------------------------------BO--------------------------------------------------------3.010

3.011---------------------CO--------------------------------------------DO--------------------------------------------------------3.010

3.0115-------------------DO-------------------------------------------DO---------------------------------------------------------3.010

3.012---------------------EO--------------------------------------------FO---------------------------------------------------------3.010

3.0125-------------------------------------------------------------------FO----------------------------------------------------------3.010

3.015---------------------------------------------------------------------LO----------------------------------------------------------3.015

3.020---------------------------------------------------------------------BB----------------------------------------------------------3.020

3.021---------------------------------------------------------------------DD----------------------------------------------------------3.020

3.022---------------------------------------------------------------------FF-----------------------------------------------------------3.020

 

I hope this prints out in useful fashion

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I do not understand the piston code you have of "E" for cylinder 5.

Having checked several of my copies (5 of them from 1934 to 1940's )  and all do not  show a letter "E".

All copies show same info.

I did copy the codes, and double checked them, unless there is a misprint in all of those years.

Or someone had a stamp on the piston line and used a stamp for the valve chamber.

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Here is the number 1, and number 8 pistons. E is the most common letter, with just two pistons having the D stamping. I did not find any stamps on the block surface, next to the cylinders. I will pull the two covers from the side of the block, and get to the valves. Thank you for the information you have posted. Everything looks to be in good condition. Engine would have had over heating problems if not cleaned out, all of the cooling passages in the head to block were half clogged, with some being totally plugged up. And block was half full of rusted chunks of casting, and 84 years of collecting other stuff?

engine and pistons 013.jpg

engine and pistons 014.jpg

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I was guessing it had to do with installing the piston, marking the direction the piston was to be installed. All of the dots on the piston tops, point towards the valves.

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Good of guess as any.

I suppose those that built those engines were not mechanics.

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The graphs posted just highlights that all engines were not created equal. I have read with other makes about different sizes of 'standard' bores and pistons and rings to fit.

 

 

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The valve chamber  is stamped as follows. Cylinder #1 D,  #2 D,  #3 D,  #4 C,  #5 D,  #6 C,  #7 D,  #8 D.  So the valve chambers that have a stamp of D,  have the pistons stamped E.  And the valve chambers that have a stamp of C,  have pistons stamped D.   D sounds a lot like E, and C sounds a lot like D. To funny if stamps on valve chamber should match pistons. This is film from the factory. Going by the design of the front fender, it might have been filmed in 1934, same year as the car.  The person that screwed up, just might be seen here.  

 

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On ‎11‎/‎11‎/‎2018 at 12:47 PM, Bloo said:

It's probably the pin that keeps the piston rings from turning.

 

Hmmm, I always try and turn the ring gaps as far from each other as possible.

Maybe there are pins to do that in the lower grooves as well.

But I always thought that rings would want to move some.

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40 minutes ago, JACK M said:

Hmmm, I always try and turn the ring gaps as far from each other as possible.

Maybe there are pins to do that in the lower grooves as well.

But I always thought that rings would want to move some.

 

It is probably one pin. Hudson kept doing this all the way into the 50s If I am not mistaken. Yes, they are all lined up.

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Learn something every day.

I don't recall ever rebuilding a Hudson, but there are a lot of things I don't recall anymore.

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