Bob,
>what's different between your 70 B and my 71 B. My TD, on the other hand,
>never pings on any octane regardless of where the timing is set. Also, when
Well, I think if it's a 71 Head (18V) you have the 39cc combustion chambers
= higher compression ratio. The manual quotes 9.0:1 for a HC motor (I can't
calc that 9.0:1 at all, can only calc 9.34:1 - no one's enlightened me to
other motor differences besides the .5cc block cutout on 18v's and the
manual doesn't mention anything else either. I'm *guessing* the HC pistons
had a deeper dish than earlier HC pistons which had a 6.25cc dish).
Have you had porting work done on the head to increase airflow? Has the head
been skimmed further decreasing the size of the CC's and upping the CR?
Porting the head will mean you are getting more mixture into the motor, and
that can cause pinging too, because the motor becomes more efficient. Even
if you don't change the CR, if you just flow the head you could end up with
pinging. Someones got the same problem on the Technical BBS. You can try
adjusting the timing, retarding it.
Answer: Move to Australia and use 96 octane Super leaded. <G> I'm going to
run 97 premium unleaded on my rebuilt motor after the head work is done.
Cheers,
Neil.
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