[Amc-list] Re; 327 Ramblings (Also I-6?)

["John Elle" <johnelle@xxxxxxxxx>]

 SNIP
Isn't there a 1.55" chevy valve? Exhaust? Wouldnt' that fit
intake better?
Snip
 
Seems to me that a few of the advantages to go with Chebby 
valves on the later V-8s might and I re-emphasize might 
cause I have not taken the time to look it up but would have
to or could if someone was interested is that the Chebby 
valves are the right length so that they will fit into the
same space in the head/valve train components that the AMC
valve does. However there are two things that make them 
better and one is that the are a bit smaller in diameter. 
This requires that a valve guide be sleeved to neck it down 
so it can be used. This is not unknown in head rebuilding 
circles so not a problem. However internal to the port the
there is more room 'cause the valve stem is smaller so you
have in creased port size with out any further machine work
and also the valve is lighter making high rpm work more 
efficient. Of course this does raise the question of how 
tight you are going to twist an AMC 327 or so V8 or an I-6
so that might just be a bit moot. 
The second reason is the later V8's valve seat is ground 
at a shallower angle than the Chebby valve seat. Later 
V8's do not use a hardened valve seat, but the head is 
induction hardened not needing a hardened valve seat so 
when you regrind the valve seat to a Chebby size. The hole 
in the head will be larger because you are steepening the 
valve sea angle when you use a larger Chebby valve just 
because you are regrinding the seat to Chebby specs.
Thus you have better breathing due to the use of a 
larger valve.
However this advantage only becomes an advantage when
you are twisting the AMC327 or AMC I-6 tighter so if
you are not twisting it tighter I guess you can ask
yourself whether these are advantages after all! 
The logical next question would be does the early V8 use
an induction hardened head and also does the I-6 in any 
of it's permutations?
Smoke stated in his engine building dissertations that an 
engine is an air pump. The amount of air you can get it 
to pump is an indication of the amount of horse power it 
will develop. 
Thus there are two ways of getting your engine to pump 
more air. Build it bigger or twist it tighter. Both 
solutions may require a bit of a budget to accomplish
and on the street there is only so much rpm that is 
useful, the rest is over kill. 
My own experience building a street I6 is with using 
an AMC-258 with a stock head and an Iskenderian cam. 
It will do 75mph in passing gear and shift hard to 
high. It is not as hot as the 225 Slant 6 I once built
but this one will pass smog with out any adjustments, the 
slant 6 did not have too. In addition I am running a bit 
over 9:1 Compression which is compatible with 91 Octane 
high test. The Slant 6 needed 101 Octane to be happy and
it was available at the time and used 13:1 compression. 
John. 
 
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