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August 02, 2004
Jens....STOP!!!
Your chasing yourself in circles here.
The variation in cooling temps with the
mixture variations, along with appearance
of the plugs and most of all, detonation/
pre-ignition (with octane changes thrown
in for good measure) suggest the engine
is operating on the borderline of self-
destruction, in short time.
Saving pennies on octane is extremely
penny-wise, pound foolish. With a tuned
unit utilizing high rpm's a good part of the
time, "economzing" on octane can shortly
become extremely expensive.
Your "tuned" engine is
an investment. Feed it a proper and appropriate "nutritional" diet. :):)
May I suggest.....
...firstly, you don't know the compression
ratio. Thus, think conservatively and
considering the problems you are now
having, use only 98 octane. Forget about
95 entirely. Given the symptoms, consider
the compression ratio higher than you think it is.
Secondarily, get the ignition timing sorted out and methinks everything
else will fall into place rather quickly.
Using a programmable timing light,
set max advance to 30 degrees. If you
cannot do this yourself for any reason,
have it done by a professional mechanic
using a programmable timing light, dyno
or whatever. You should go no further 'til
this is attended to 'cause your motor
is talking to you and telling you it's
ignition timing is most likely overadvanced.
Thirdly, check the intake system for
vacuum leaks by spraying the intake
system with carb cleaner. Fix any
vacuum leaks before....
...setting the mixture, using a fresh set
of NGK BPR6ES (or EV) spark plugs
or equivalent, using the "rich" needle
as given in "the book" (H6). Slightly
"richer" would be AH1 or AH2 in that
order but my guess is the H6 will be
fine using the foregoing plug after the
max ignition advance has been properly
set and any and all vacuum leaks are
taken care of.
One caveat.....if the static compression
ratio is greater than 10.5-1, you may have
to go to a BPR7ES (EV) or equivalent
colder plug. 10.5-1 is about it for 98RON
with the cast iron head.
Subsequent to the foregoing....
you can further "cool" the combustion
process by going to the more rich AH1
or AH2 needles (in that order) and/or
retarding the total timing to 28 degrees
or so, at the cost of a little performance
in terms of "torque".
Good luck...get it done...report back and
let us know what happens. You owe me
big time for saving your motor!! :):):)
Cap'n. Bob
'60 :{)
PilotRob@... 33258
Posted on August 2, 2004 01:48 PM
Posted to category(s) Carburetor | Cooling System | Cylinder Head | Electrical System | Engine (external) | Engine (internal) | Exterior | Fuel System | Ignition System | Intake System | Technical Info | Transmission | Tuning
