ARC Billet Head

Lkerley

Member
Is there any benefits on a s/a motor adding a Finned billet head or is benefit not worth the price ...stock valves,.060 over,stock lift Dyno cam.if so what cc.
 

OVALTECH1

Member
the combustion chamber on the one ARC is considerably smaller. I always liked that one. I have one of the higher compression small chamber Briggs head
 

alvin l nunley

Premium User
[Q
I'm going to guess that it does add value. How much? That depends, I suppose, on how good a set up man you are. If you know how to tune to take advantage of the head, I can imagine some gains. I'm thinking, if you just bolted it on and don't change your tuning procedure, the gains could be minimal. There's no doubt that a billet head can transfer more heat from the combustion chamber. I'm guessing that would mean you could run it leaner, with a colder plug and higher CHT readings. Not that the CHT tells you much, I prefer the EGT, but whatever.
One thing, it costs money to go faster, but, as the gains become smaller and smaller, the price goes higher and higher for each increment of gain.
UOTE="Lkerley, post: 803128, member: 22706"]
Is there any benefits on a s/a motor adding a Finned billet head or is benefit not worth the price ...stock valves,.060 over,stock lift Dyno cam.if so what cc.
[/QUOTE]
 

CarlsonMotorsports

Premium User
There are other gains that would be greater than adding the head, but it certainly will not hurt power, (long rod, Wiseco piston, bigger cam, bigger valves, good portwork, etc) BUT they're a beautiful addition to any engine.


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There's no doubt that a billet head can transfer more heat from the combustion chamber. I'm guessing that would mean you could run it leaner, with a colder plug and higher CHT readings.
Maybe to elaborate just a touch on Al's statement

Two of the most common alloys (A356 for castings, and 6061 for billet) have absolutely identical specific heat capacity, though thermal conductivity is a couple percent better in 6061.

Point being: when it comes to thermal conductivity and capacity, simply saying "billet is better than cast" is not necessarily true -- it depends on a number of other factors like alloy, mass and design/shape.

PM
 

Lkerley

Member
[Q
I'm going to guess that it does add value. How much? That depends, I suppose, on how good a set up man you are. If you know how to tune to take advantage of the head, I can imagine some gains. I'm thinking, if you just bolted it on and don't change your tuning procedure, the gains could be minimal. There's no doubt that a billet head can transfer more heat from the combustion chamber. I'm guessing that would mean you could run it leaner, with a colder plug and higher CHT readings. Not that the CHT tells you much, I prefer the EGT, but whatever.
One thing, it costs money to go faster, but, as the gains become smaller and smaller, the price goes higher and higher for each increment of gain.
UOTE="Lkerley, post: 803128, member: 22706"]
Is there any benefits on a s/a motor adding a Finned billet head or is benefit not worth the price ...stock valves,.060 over,stock lift Dyno cam.if so what cc.
[/QUOTE]
This is on 87 octane.that might change the picture
 

alvin l nunley

Premium User
Maybe to elaborate just a touch on Al's statement

Two of the most common alloys (A356 for castings, and 6061 for billet) have absolutely identical specific heat capacity, though thermal conductivity is a couple percent better in 6061.

Point being: when it comes to thermal conductivity and capacity, simply saying "billet is better than cast" is not necessarily true -- it depends on a number of other factors like alloy, mass and design/shape.

PM
Assuming a perfect casting.
I once broke a McCullough piston part. Wisco I think. You should try it, big cavities in the aluminum. It was not a perfect casting, far from it. I have to believe that with those kind of flaws in the casting, heat transfer would be impaired.
 

CarlsonMotorsports

Premium User
Even with the billet head, the flathead is an extremely low compression engine. You're probably in the 6 to 7:1 ratio. Not exactly high compression by any stretch.
 

OVALTECH1

Member
How much do they gain with the different rod length combos and/or stroker crank combos? Can you get these up to say a 9:1 ratio?
 

CarlsonMotorsports

Premium User
The problem is that the CCs of the combustion chamber don't change. You can increase cubic inches, you can increase rod length, piston speed, etc, but you can't decrease the size of the combustion chamber much more without killing all of the airflow. That's a limitation of the flathead design.
 

Lkerley

Member
The problem is that the CCs of the combustion chamber don't change. You can increase cubic inches, you can increase rod length, piston speed, etc, but you can't decrease the size of the combustion chamber much more without killing all of the airflow. That's a limitation of the flathead design.
That's what I was thinking it's 1 cylinder not 8
 

CarlsonMotorsports

Premium User
Also consider that going from standard bore to +.030" is one third (1/3) of 1 cubic inch.
It's not like we're boring a 350 SBC .030" over and coming up with a 355CI!
 
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