Peter,
I can't help with the first question, but I have a suggestion
for
the second. I think your compression ratio may be too high. You
mentioned
your engine was rebuilt with Mahle pistons, which I remember from my
Volkswagon rebuilding days were often used to raise the C. R.
(compres-
sion ratio) for a higher output of your engine, as you mention you
have.100 hp at the wheels is quite good.
You also have written that you had the head milled down which is
usually done to raise the C. R. to get more power. The mention of a
"modified" head gasket only furthers my suspicions. You should try to
contact the shop that milled down the head and find out how much they
removed, for if it is over .1 inch (.25 cm?) the C.R. will problably
exceed what pump gas could handle.
As a test you should try running "racing gas" which is available
in the U. S. at a few gas stations. This gas is very high octane fuel
of a rating number which I currerntly don't remember exactly but
think
was in the neighborhood of 110. As I recall, it was available here at
certian Union 76 stations. At any rate, even if you use octane
booster
from a can, and the pinging goes away, you have found the problem.
The reason the pinging begins at 3000 RPM is because that is
prob-
lably when the ignition timing is advanced by the mechanical (centri-
fical) advance in the distributor housing.
For solutions I would suggest maybe getting a different dist. so
you could reprogram the mech. advance of ignition timing. I think the
Mallory dist. is adjustable.Or you might just want to keep all that
power and
find a fuel or fuel additive to elinate the pinging. A last
suggestion
is to rebuild the engine using two head gaskets (not really wise) or
a stock head to reduce the C. R.
An idea that just hit me (as I ramble on) is to check your fuel
mixture. A too lean mix will ping. And a too rich mixture may help
re-
duce pinging if the C. R. is too high.
I hope I'm wrong and your problem is just somethig simple. Good
luck.
JOE IV
TR 250
P.S. I also wonder if switching to a wilder camshaft would help by
allowing better engine exhaust ventilation?
|