In a message dated 96-09-13 01:33:37 EDT, you write:
<<
The original head places the valves in a chamber with an outside
perimeter that defines an area about 2/3 the area of the cylinder
perimeter. The remaining 1/3 area is flat, flush with the bottom of
the head.
The new head has the same chamber, but the boundary between the
chamber and the flat area is beveled, not 90 degrees. This, I
assume, results in greater volume/less compression, as has been
talked about in recent mailings.
>>
Charlie-
To my recollection, ALL the TR3-4-4a heads should have had an angle present
where the squish area turns into the combustion chamber. First thing you need
to do is to measure the depth of both of your heads. Measure between the face
that mates to the block and the machined area where the valve cover gasket
sits (also can use the upper edge of the boss where the head studs go). Now
we get to the tough part...according to my memory banks,( now wait...what is
it that goes first ? I forget...<g>) the stock thickness is 3.330". I'll bet
that your old head without the angled area will be thinner as this would be
the only way that the angle could "disappear". In order to make the angled
part of the squish area "disappear", quite a considerable amount must be
removed from the head (approx .150" or so). If you find this to be the case,
your new head is going to make a significant change in the amount of power
you are used to (less). But it will probably run cooler and not ping as
easily.
If your new head just appears to have a "larger-wider" angled area compared
to your old head, and you old head really does have an angled area, then
perhaps it has been the one that has been modified, and the area in question
has merely increased over the stock size. Again check the thickness of the
head. Any head which measures more than .080" thinner than the stock
thickness is going to need some additional work done to it to keep it
"streetable". Specifically, the shrouded area below the intake valve must be
ground away, and the aforementioned angle
must be ground in again.
Hope I haven't confused you too much...
Nick in Nor Cal
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