Head button material preference?

[RaceMechaniX]

Guys, is there a preference for aluminum grades for making head buttons? Is standard 6061-T6511 suitable or a better alternative?
Thanks,
-Tyler

 

[John Beardslee]

Tyler, I’ve used 4032 Aluminum per Jack O’Donnell for many years without a problem.
John

 

[RaceMechaniX]

Thanks John, That's common piston blank material. A little difficult to find in smaller bar stock quantities. Do you have any decent sources?

 

[John Beardslee]

Last I bought from McMater Carr many years ago, 3 foot x ?? Dia. It been awhile but I think it’s 1.5” so I can use it for all engines.

 

[Charles Perdue]

Second that.......but it is tough on tooling because of all the silicon in it. If you do very many, use carbide.

 

[Terry Keeley]

I like 7075 just because the threads are stronger. Ever have a head strip?

 

[Charles Perdue]

The reason that Jack O'Donnell recommended 4032 is that the expansion rate of 4032 closely matches the expansion rate of the brass sleeve.

If the head expands faster and more than the sleeve it will open up the top of the sleeve away from the piston and cause the engine to loose compression.

Charles

 

[Mike Hughes]

I have used 2011 with good result. Easier to find. I liked how it machined. Mark Anderson and I bought 6' of it to split years ago. Still have about 1' left.
Mike

 

[Charles Perdue]

The reason that Jack O'Donnell recommended 4032 is that the expansion rate of 4032 closely matches the expansion rate of the brass sleeve.

If the head expands faster than the sleeve it will open up the top of the sleeve away from the piston and cause the engine to loose compression.

Charles

For those of you that may not know, Jack O'Donnell and I were very close friends for over 40 years....we had many, many conversations about our toy motors.
He was one of the top 2 cycle engine experts in the world.

 

[John Beardslee]

For those of you that may not know, Jack O'Donnell and I were very close friends for over 40 years....we had many, many conversations about our toy motors.
He was one of the top 2 cycle engine experts in the world.

Who knew!!!! Sorry Charles, not many of us left!!! Can you imagine friends for that many years! For me it’s the most difficult thing about aging, losing so many friends that share the same passion for high performance 2 cycle engines!!!

 

[Terry Keeley]

I'm thinking about trying RSA431.

Hmmm...

 

[RaceMechaniX]

Terry, thinking about your engine dyno have you tried making a couple pulls and sweeping your engine head temp?

 

[Charles Perdue]

Who knew!!!! Sorry Charles, not many of us left!!! Can you imagine friends for that many years! For me it’s the most difficult thing about aging, losing so many friends that share the same passion for high performance 2 cycle engines!!!

Yes, it is not the thought of getting old that bothers me....like you said, it is loosing the long time friends.

 

[Terry Keeley]

Terry, thinking about your engine dyno have you tried making a couple pulls and sweeping your engine head temp?

So far CHT is running around 300F, that's with the thermocouple mounted to a ring lug under the plug. IR gun can show 25-50* less.

 

[Terry Keeley]

Did a little more digging on this while having my morning coffee.

Below are the thermal expansion (micron/C*) and thermal conductivity (watts per meter-kelvin) for some of our materials:


360 brass: 20.5 / 115

2024 aluminum: 23.2 / 143

7075 aluminum: 23.6 / 130

RSA431: 15.5 / 120

4032 aluminum: 19.4 / 140


You can see the expansion rate of 4032 aluminum is very close to brass, maybe why Jack liked it best in his tether cars. Or maybe he used 4032 sleeves as well?

I also chatted with Neal Lickford on this (worked with Henry Nelson for years) and he figured with water cooling the head would always stay cooler than the brass sleeve, just another consideration. Nelson's use 2024 BTW.

Interesting that brass doesn't conduct heat very well, wonder why guys are using it for heads?

Think I'll save my 431 for making pistons.

 

[DougSick]

In our colder northern waters we have had good success with brass buttons. Same expansion rate as the brass liner so no issue with stretching the liner. Brass holds the heat better.

 

[Charles Perdue]

Did a little more digging on this while having my morning coffee.

Below are the thermal expansion (micron/C*) and thermal conductivity (watts per meter-kelvin) for some of our materials:


360 brass: 20.5 / 115

2024 aluminum: 23.2 / 143

7075 aluminum: 23.6 / 130

RSA431: 15.5 / 120

4032 aluminum: 19.4 / 140


You can see the expansion rate of 4032 aluminum is very close to brass, maybe why Jack liked it best in his tether cars. Or maybe he used 4032 sleeves as well?

I also chatted with Neal Lickford on this (worked with Henry Nelson for years) and he figured with water cooling the head would always stay cooler than the brass sleeve, just another consideration. Nelson's use 2024 BTW.

Interesting that brass doesn't conduct heat very well, wonder why guys are using it for heads?

Think I'll save my 431 for making pistons.

Jack used brass or other materials for sleeves but no aluminum in the tether cars. Only brass in his marine engines.


Doesn't Nelson run aluminum sleeves in some of their engines????

Charles

 

[Terry Keeley]

Yes, I was told Henry uses 4032 for their aluminum sleeves.

 

[RaceMechaniX]

Thanks for the input guys. I will try to source several different materials and see what I can come up with.

 

[John Beardslee]

Yes, I was told Henry uses 4032 for their aluminum sleeves.

Didn’t he have them aluminum oxide coated or what many call hard anodized?