Timing

[steven d. ferguson]

Okay, let me get this straight. I have paid close attention to the
stories
regarding setting timing and I have a general question: Does timing
require
retarding when travelling from high altitude to low? And thusly, does
timing
require advancing when travelling from low altitude to high?.....
Larry,
Under heavy load the timing will retard simply because the engine
vacuum will be so low. If you hear pinging, you might want to retard
the initial timing a bit though, at least until you get out of the
driving conditions that are causing it.. I've been reading the posts on
the knock sensors and I'm convinced that they are the way to go. It's a
small investment to protect your bottom end bearings and pistons. I've
pulled apart quite a few engines that have gone through severe
detonation and the crank bearings are showing copper and the tops of the
pistons are badly pitted. Each ping is the equivalent of striking the
top of the piston with a ball peen hammer. Now consider doing this
before the piston reaches TDC. It really takes a heavy toll on
bearings.
To answer your original question.....unless you have some automatic
retard device installed, you need to be prepared to advance or retard
your timing to match driving conditions and fuel quality.
HTH,
Steve

 

[steven d. ferguson]

Consequently, it's hard for me to understand that timing alone is enough
in the
GMC to compensate for high altitude driving. Do owners of GMC's that
are based
up above 5,000' or so just adjust timing to compensate for altitude?
Richard Waters
Richard,
It most likely isn't enough but it's solving part of the problem.
Rejetting just isn't that easy for us shade tree guys running Q-Jets and
some of us don't have EFI or laptops that permit us to change our
fuel/timing maps.
AND I still love those Corvairs!
Steve F.