[TR] Aluminum head?

Michael Porter mdporter at dfn.com
Mon Sep 2 19:50:29 MDT 2019


On 9/2/2019 7:10 PM, Paul Dorsey wrote:
> Gotcha!  I may be dumb but   I I am dumb, but,I’m no dummy, I don’t 
> have an aluminum head on my motor. Do theymake aluminum heads for our 
> motor or do they? Anyway they’re out of my price range.
>   As I was loosening the bolts that hold the head on,  I got to 
> thinking, I wonder if there is a sequence for loosening these head 
> nuts .   Metal bends, You know. Perhaps that is more critical for 
> something like aluminum heads.


There have been attempts at making aluminum heads for the wet-sleeve 
engines, but they've been largely unsuccessful, for one major 
reason--they have been designed as analogues of the cast-iron head done 
in aluminum--dimensionally and in configuration, they're duplicates of 
the original.  For that reason, they don't have the mechanical strength 
of the cast-iron heads, and can't force down the liners as well as the 
originals, and therefore tend to leak.  There are a couple of people on 
the lists who have installed them on their engines.

The problem is beam strength.  Cast aluminum simply isn't as strong as 
cast iron, so if the dimensions are identical, then the cast aluminum 
head will tend to bend around the liners rather than punching them down 
into the figure-eight gaskets.  That produces leaks at the head gasket.  
An aluminum head for the engine is a good idea, but not as currently 
done.  Future examples really should consider radical redesigns to 
accommodate wet-sleeve construction, in the way of increasing beam 
strength.  I've done some preliminary work on just that--thicker, taller 
heads in which the outer perimeter is raised and thickened, using a 
flatter cast valve cover socketed into the upper surface so it occupies 
the same space.  And, of course, adding crossflow port configuration, 
which should have been done right from the start.  It also wouldn't hurt 
to machine the block lower cylinder lands smooth and machine the 
cylinders for o-rings, which solves the figure-8 gasket compression 
sealing problem.  The cylinders only need to stand proud enough (a 
thousandth or so) to ensure that the cylinder head locks them to the 
block so they don't travel up and down with piston motion.

Something like that would work pretty well, methinks.


Cheers.

-- 


Michael Porter
Roswell, NM


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




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