"basskisser" wrote in message
om...
"Calif Bill" wrote in message
ink.net...
"Bob" wrote in message
...

My Volvo AQ130C 4 cyl/130 hp engine (a factory rebuild with about 85
hours on it now) pings when I am at sea level and running above about
4400 rpm...not a real bad ping but a ping none the less that concerns
me...this despite using 91 octane gas with octane booster added to it.
It does not ping at all at on Lake Tahoe (6200') using the same
gas/octane booster. I checked the ignition timing today while out for
a cruise on Lake Tahoe and it was right on spec, which does not
surprise me since the engine was installed and tuned at Lake Tahoe.

My question is this...does altitude affect ignition timing? I guess
one way to find out is to put the timing light on it next time I have
it down at sea level.

Any other ideas why it might ping at sea level?

Thanks!

You can run more advance at altitude. We use to run about 6 degrees
more
advance on the race car when running at Stead AFB.
Bill


Learn to read. He asked, simply, whether altitude changes ignition
timing. Answer is also simple...no.

The question was "Does altitude affect ignition timing?" And yes altitude
does AFFECT timing. Affect not change. You look very stupid again.

Geoff 93 RRC wrote:

:Try a colder heat range plug. Are they the correct ones for the marine
:motor? The carburator probably needs rejetting otherwise - just take it off
:and take it to a carb shop.

Thanks. I'm using NGK BP7HS plugs now, which is what NGK says is
correct for my engine (Volvo AQ130C I/O). I'll try a set of NGK BP8HS
and see if they help.

Update:

Thought I would first try a colder spark plug so I bought and installed
a set of the same type of NGK plugs I was using, just one step colder.
I also checked the engine timing...found it to be very close to spec,
perhaps at most a few degrees advanced (spec = 27-29 BTDC @ 2000 rpm)
and adjusted it to the low end of the spec.

I also installed my StingRay hydrofoil since I was going to be taking 3
other adults in the boat and wanted to insure as ease of planing as
possible.

Results:

Went out on the Sacramento River on Saturday. No pinging at all, even
at WOT (5000 rpm, 31 mph). As good as performance as before installing
new plugs and timing adjstment. Only heard pinging once...when I made a
tight circle at high speed...would suspect the extra load due to the
turning caused that.

I will be taking the boat out again this weekend with just 1 other
adult so I will remove the StingRay, but I can't imagine it had
anything to do with the lack of pinging.

I will also be checking the spark plugs after some more use to be sure
they aren't oil fouled, which I understand results from too cold of a
plug.