James head gaskets

[T. Cotten]

Before we declare aluminum absolutely superior, Folks,..

Forgive me again for using H-Ds as an analogy, but please note that (according to Palmer's) H-D used cast iron heads as standard for '37 through '48 flatty 74"s, with aluminum as only an option for '40 and later. Aluminum was only standard for two years of 80" production, ending in '41. The difference in application is based upon compression.

Why was cast iron retained over aluminum if it did not have advantages?

Note also that their 45"s used cast iron from '37 all the way through '73, with aluminum used only on medium and high compression models, from '40 through '52.
So cast iron was retained for twenty-one years after aluminum.

The implication is that aluminum is only of benefit for higher compressions.
Ironically, the H-D parts book does not list different kinds of gaskets for the big twin flattys, however it does for the 45"s, and the aluminum head gaskets were "Felpro-style" composites.
Thus, the 'rule of thumb' as I was taught, was copper for cast iron, and composite for aluminum.
So, apparently the durability of the gasket under compression was not the deciding factor.

Jerry!
Heat travels from the hotter regions to the cooler. The head is certainly hotter than the cylinder, with higher compressions at least.
Once again I respectfully ask: Do we want a head gasket to insulate, or conduct?

....Cotten
PS: I only post on forums where where I am not "trolled".

[1950Panhead]

Why was cast iron retained over aluminum if it did not have advantages?

It was much cheaper, if you wanted aluminum heads you had to pay for them.

The thermal conductivity of pure aluminum is 124 in the chart.
The thermal conductivity of cast iron is 27 to 46 in the chart.
Aluminum conducts heat 2.6 to 4.5 better then cast iron.
http://www.engineeringtoolbox.com/th...als-d_858.html

Heat travels from the hotter regions to the cooler.

True.

The head is certainly hotter than the cylinder, with higher compressions at least.

The aluminum head may absorb more heat from combustion then iron cylinder but it can release the heat faster.
Pan head and pan cylinder temps have been checked with ir guns at 300, same temp with composite gaskets.
I will check my chief this summer.

Once again I respectfully ask: Do we want a head gasket to insulate, or conduct?

My guess is you can get rid of heat faster with a copper gasket, I don't have proof.
I'll build the next flathead with one of each.

[T. Cotten]

Again using a milwaukee machine for analogy,

Here is a heat chart for the medium-compression aluminum-headed WLA.
Flattys run most efficiently at about 100F hotter than an OHV;
Aluminum heads have larger finnage than cast iron for both marques, I believe.

My suspicion is that they wanted to disperse the higher compression heat without conducting it to the cylinder, however the cast iron heads provided a more uniform heat at lower compression, using it to stay in the efficient range of a flatty. Note that the head is only about a hundred degrees hotter than the cylinder walls, so cast iron may have been virtually the same.
One of the banes of flattys is uneven distortion of the bore, due to the valves on one side. Utility machines wanted longevity, and less carbon build-up, than sport machines, and that is what I believe prompted H-D to continue with cast iron.

....Cotten

[1950Panhead]

Flattys run most efficiently at about 100F hotter than an OHV;

Why is that?

Aluminum heads have larger finnage than cast iron for both marques, I believe.

The 40 aluminum head has 41.5 percent more surface area per Harley.
Indian heads also have more surface area.

[T. Cotten]

Well Jerry,

Flattys are supposed to be hot so they can burn lower octane fuels, I guess.


I just cracked open the Armored School book where the heat chart came from, and found a passage stating the "copper head gasket can be reused"!
Yet my NOS gasket kit in ordinance packaging has composites upon an aluminum 'foundation'.

Like I said, I'm conjuring.

....Cotten

[T. Cotten]

Since this topic has been revived on the forum, Folks,,,,

It might be best to continue here.

Jerry stated "If you have copper gaskets the heat can move from the cylinder to the head then to the air.
If you have composite gaskets the heat transfer is inhibited and stays in the cylinder."

The problem Jerry, is that heat only goes where it isn't. If the head is hotter, heat goes to the cylinder.

....Cotten
PS: I like all forums, but that one ragged me off, begged me back, and then a hostile mod ragged me off again. It no longer allows me to even log on, so it must be a formal ban.

I held the record for bans from vintage sites, but it appears https://www.jockeyjournal.com/forums/ is under better management! Hope to participate there soon,...