re: top dead center with a dowel question

["Dan Curtis" <d.curtis@xxxxxxx>]

Re: {FORGED?} Re: Finding TDC with a dowel
Date: Wednesday, December 1, 2004 02:26 AM
From: Tom Jennings <tomj@xxxxxxx>
> On November 30, 2004 Brian Hagen wrote:
>
> > I think you misread my post.
> >
> > If i have the engine set at TDC according to the timing mark, and the
> > rotor
> > is set at #1 cylinder.. it wont run.



>You never answered the basic question:
>When you set the #1 piston to TDC power stroke, do the marks
>line up, or not? If not, how far are they off?

The timing marks should be pretty close to lined up perfectly at TDC unless
your timing chain gears
are not aligned properly.  Misaligned timing chain gears can occur either at
assembly by using the
wrong mark on the gears or if the chain or gears themselves get very worn
and stretch to the point
where the chain "jumps" a tooth or two on the gears. Usually, if it is that
worn, you will
hear substantial noise from the chain rumbling or even hitting the sides of
the front cover.
This can be caused by a variety of things such as poor oil flow in the chain
area, running the
engine with low oil in the pan but most likely would be caused by running an
old and semi-worn
out engine real hard with high revs and a pretty substantial misfire.

You should also be sure that you were, in fact, on the compression stroke
and the easiest way to
ensure that you are on the correct stroke is to use a compression gauge to
be sure you have full
compression when the #1 piston is at TDC.  Also, at the risk of stating the
obvious, be sure
you are measuring #1 which is the front drivers side piston.

If the lines don't line up on TDC, and you should check to be sure you are
in fact on TDC by removing
the compression gauge and using a dowel in the spark plug hole to make sure
the piston is all the way
up, then the only other explanation is that your timing gear marks are
misaligned or you were on the exhaust
stroke on the engine cycle.  If the latter were the case, your timing mark
would be 180 off.  There is one
word of caution here however, some manufacturers used offsetting the
internal timing gears in later model
engines to create an internal timing retard for early emissions control,
mostly in the mid 70s.  As I recall, this
was the case on a 74 SS 350 Nova that I had but I am not sure if AMC did
this or not.  Then again, they also used
plastic gear teeth and my engine did in fact jump 3 teeth on the timing
gears after a hard day at the track at New England dragway.

Best Regards,
Dan Curtis
Cell 602 317 2018
d.curtis@xxxxxxx