RE: 4 cylinder head question

["Peter Webb" <webb.p@xxxxxxxxx>]

Also from the Kartalamakis book, to measure the combustion chamber volume,
remove the cams and seal the valves of #1 cyl with grease.   Take and move
the #1 piston to TDC and seal the upper ring to the liner with grease by
squirting it around the piston until it's flush with the top of the piston.
Place a head gasket and head on the studs and torque.   Fill a 100cc syringe
with water.   Squirt the water through the plug hole until the water comes
to the bottom of the plug hole.  Subtract the amount of water in the syringe
from 100 and that's the volume of the combustion chamber.   Water is used
because it won't dissolve the grease and break the water tight seal.   Use
the syringe and a tube to suck the water out before dismantling.

How to Power Tune Alfa Romeo Twin Cam Engines for Road and Track by John
Kartalamakis and Weber Carb's by Pat Braden are 2 essential books for the
Alfa builder.   Kartalamakis contains some references from the Autodelta
Comp Handbook.   If you can find a copy of the Comp Handbook, that's the
Holy Grail of go fast documents.

-Peter


-----Original Message-----
From: owner-alfa@domain.elided [mailto:owner-alfa@domain.elided]On Behalf Of
Jon Pike
Sent: Monday, June 09, 2003 10:20 PM
To: alfa-digest@domain.elided
Subject: Re: 4 cylinder head question


>Can someone who has a head off the engine measure the combustion chamber
depth and
>diametre?  The measurement can be either in mm or inches, I can convert
into the form I
>require.
>

Well.. to the best of my limited abilities, and accuracy of a cheap pair
of calipers...  I went to the head off of the basket case motor I'm
rebuilding, convienently located on the breakfast nook table, (it's good
to have a VERY understanding wife!) and measured as follows:

Thickness of head (for reference)             4.405"    111.89 mm

Outer diameter of combustion chamber    3.297"    83.75 mm

What I'm calling the "inner angle diameter" is a narrow surface kind of
like a valve seat, that extends from flush with the surface of the
head,  to where it stops being a flat angle and joins the original
hemisphere.  Measurement is at the beginning of the "hemisphere".

Inner angle diameter                                 3.149"    80.0 mm
(except #4 which was79.62 mm!)

And here it gets more complex,  there are smaller hemispheres around the
valve seats, #1 and #4 are large and off center,  #2 and #3 are smaller
and more evenly centered on the valve seats.  Both types come together
at the spark plug hole, kind of leaving a angled ridge in the middle.
Rather than try to figure out something else, I measured down from
approxamately the center of the chamber, to the highest point of the
ridge.  Usually this was a few mm from the spark plug hole.  This varied
a fair amount.

Depth of chamber                #1    31.43 mm
                                           #2    30.96 mm
                                           #3    31.06 mm
                                           #4    30.99 mm

BTW engine is a 2L, 72-74 vintage.

Hopefully that gives you something to play around with.

Jon and Marcia
77 Spider
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