In a message dated 96-09-01 20:54:00 EDT, you write:
>The tone of your message makes it sound like the car may become unbearable.
>Maybe there was more to the Grassroots Motorsports article than I thought!
>The
>chamber cc'd at 56 after the reface, and before any further grinding. With
87
>mm
>pistons, 0.013" deck height, and 0.020" gasket thickness, this gave me a
>calculated compression ratio of about 9.9. After I radius in the intake
>valves, grind the squish areas back in, and eyebrow the cylinder liners, it
>seems like my compression ratio would drop substantially from this number.
>I
Dave-
Sorry, didn't mean to intimate that your compression was going to be a
problem, just that I think that about 10 to 1 is about all any motor can
handle these days without major "tweaking" Sounds like you are on the right
track so far. If there is any lip left below the intake valve after you have
the head milled, grind it completely away. The combustion chamber wall next
to the intake valve should be straight up and down. Regrind the chamfer
across from the spark plug so that a straight edge across it would intersect
the top of the combustion chamber about 1/2 of the way across. The sooner you
can get the flame front down on the piston crown, the better on this engine.
The gas flow will not exactely follow the geometric angles, due to boundary
layer flow resistance, but that angle will cause a downward flow at the spark
plug side of the combustion chamber, which will help with the flame front
propagation, and ultimatley, the power.
What a lucky guy, to have an adjustable advance on your distributor. Play
around with slower initial curves and you may not have any pinging at all !
SU carbs will often give more than adequate response on the street, however,
we all fall prey to the "more is better" syndrome. Since the SU carbs are
smaller in cross section and feed two cylinders, they often provide the best
off the line response. I have to admit that these carbs are one of my
favorites, as they are so simple to modify and adjust, but Webers certainly
have a major "cool" quotient. Remember that, the "hairier" your cam, the
worse your low speed response will be with the Webers.
"Grinding the tail off of the cam" , refers to the cam which operates the
points in a Lucas distributor. The cam is held in with one screw down through
the top of the cam, under the ignition rotor. When you remove it, you will
find a long steel "tail" which contacts a peg when full advance has been
reached. By changing this cam (be careful as Lucas made both symetrical and
non-symetrical lobe styles) or shortening the length of this tail "ginding it
off", you can adjust the overall advance.
The Car Curmudgeon
Nick in Nor Cal
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