[TR] TR4A Aluminium Head

[Michael Porter]

On 4/4/2017 6:24 PM, Randall wrote:
>
> Check liner protrusion on both sides, and preferably get it near the top of
> the range in the book.  I would be tempted to try my "fire ring" trick as
> well.  Strictly mickey-mouse, but it's worked well for me on two motors now
> that I couldn't keep sealed otherwise (low liner protrusion on one side).

One niggle in all this....  IIRC, the heads produced of this type had 
one big failing.  They were, IIRC, dimensionally the same as the iron 
heads, and simply did not have the mechanical strength of the 
originals.  They blew head gaskets because the mating surface deformed 
rather than pressing down uniformly on the cylinders. Aluminum has 
somewhat more ductility than cast iron, so the heads were tolerant of 
more deformation before cracking, but the down side of that is they 
didn't seal well.

So, if anything, to minimize that distortion, I'd try to get the liner 
protrusion down to the lower end of the range and find a more forgiving 
head gasket.

I think Kas lamented, a few years back, why no one had done any aluminum 
repros of the cylinder heads, and this is likely the reason.  The design 
would have to be modified considerably to make it strong enough.  
Aluminum cylinder heads work just fine in other applications where the 
mating surfaces are true to each other, but those wet sleeves sticking 
up are a problem.  An aluminum cylinder head, to be strong enough, to 
have enough beam strength, would have to look considerably different 
than stock.  (The alternative would be to cast the head with a different 
material, say, a suitable alloy of aluminum bronze, which has nearly the 
mechanical strength of cast iron, but with nearly the same heat transfer 
properties of aluminum.  The down side of that is that bronzes are 
notoriously difficult to cast in complicated sections by conventional 
means because they tend to be pretty gassy, and the alternative, 
investment casting, is a good deal more expensive.  But, someone with 
access to a  5-axis CNC machine and a few hunks of machinable wax could 
probably come up with a cylinder head worth the effort.  A cross-flow 
head that was strong enough that corrected a few flaws in the bathtub 
chambers, along with fixing the thin spots that have to be pinned after 
milling, and better ports, etc., would be a real winner.)


Cheers, Randall.

-- 


Michael Porter
Roswell, NM


Never let anyone drive you crazy when you know it's within walking distance....