More Timing Woes

[nate chase]

Finally got my ping problem narrowed
down. I tried new hd springs on the
mechanical advance. No difference...
still pings even at 8 degrees. Finally,
out of desperation I tried unhooking the
vacuum adv and plugging it off as I test
drove it. It has a 10 stamped in it so
it looks like the right advance
mechanism. Lost a bit of power but that
resolved the ping issue instantly. Man
thats nice not hearing those anymore.
Hate to see what my gas milage would be
like this way! I feel pretty confident
now that the adjustable vacuum advance
will do the trick once it comes in later
today.

FYI the spring/weight kit also mentioned
that if you can't stop the ping by using
the springs supplied to look at a GM p/n
vacuum restrictor. It gives 0 vacuum
advance under load. I haven't heard of
these but assume it works like a delay
circuit or similar to a bucket of water
(ie. takes awhile to fill up but empties
out quickly). That way it would still
gives full vacuum advance once you are
up to cruising speed for good gas milage
but stops the pings.

Nate '75GB (finally on the right track)
Omaha

 

[gene]

something is just not right here. You should not need all these things to
fix this problem. The problem is somewhere else..... No one else has
variable vac advance or restrictors......

Cannot recommend what, but this is not the problem... I feel.

gene

>Finally got my ping problem narrowed
>down. I tried new hd springs on the
>mechanical advance. No difference...
>still pings even at 8 degrees. Finally,
>out of desperation I tried unhooking the
>vacuum adv and plugging it off as I test
>drove it. It has a 10 stamped in it so
>it looks like the right advance
>mechanism. Lost a bit of power but that
>resolved the ping issue instantly. Man
>thats nice not hearing those anymore.
>Hate to see what my gas milage would be
>like this way! I feel pretty confident
>now that the adjustable vacuum advance
>will do the trick once it comes in later
>today.
>
>FYI the spring/weight kit also mentioned
>that if you can't stop the ping by using
>the springs supplied to look at a GM p/n
>vacuum restrictor. It gives 0 vacuum
>advance under load. I haven't heard of
>these but assume it works like a delay
>circuit or similar to a bucket of water
>(ie. takes awhile to fill up but empties
>out quickly). That way it would still
>gives full vacuum advance once you are
>up to cruising speed for good gas milage
>but stops the pings.
>
>Nate '75GB (finally on the right track)
>Omaha
>
>
>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/

 

[emerystora]

>Finally got my ping problem narrowed
>down. I tried new hd springs on the
>mechanical advance. No difference...
>still pings even at 8 degrees. Finally,
>out of desperation I tried unhooking the
>vacuum adv and plugging it off as I test
>drove it. It has a 10 stamped in it so
>it looks like the right advance
>mechanism. Lost a bit of power but that
>resolved the ping issue instantly.

Nate - did you try checking the vacuum advance to see if the diaphram
is leaking? If you have a vacuum leak it will change the fuel
mixture and also be a cause of pinging. If you don't have a hand
test vacuum pump just hook a hose up to the vacuum advance and see if
you can hold a vacuum while sucking on the hose with your mouth.
Your description sounds as if the advance is not working. When you
get advance, the power should come back.

You might not need an adjustable advance, you might just need a
properly working stock one. I would guess that most GMCs do not have
an adjustble one and their OEM one is working OK. Mine is.

Emery Stora
77 Kingsley
Santa Fe, NM

 

[blank]

Gene,

Thanks for writing what I've been thinking. This has the feel of "taping
over" the real problem.

At the risk of rekindling the "ported vacuum" controversy, that the
distributor might be connected to an unported source or that the harmonic
balancer may have slipped comes to mind as possibilities.

You're right, Nate needs to find the "real" problem before throwing parts at
the motor.

patrick

>
> something is just not right here. You should not need all
> these things to fix this problem. The problem is somewhere
> else..... No one else has variable vac advance or
> restrictors......
>
> Cannot recommend what, but this is not the problem... I feel.
>
> gene

 

[nate chase]

Just an FYI... the $10.99 HEI module I
got from Autozone is a WELLS. Says "Made
In USA" all over the box even though the
instructions come in three flavors. The
Wells P/N is TR100 and I will just carry
it for a spare since my advance problem
(i.e.. pinging) appears finally to be in
the vacuum advance mechanism itself.

I did pick up the Accel adjustable adv
module at lunchtime (came in just like
O'Rielly's promised yesterday) and looks
to be a piece of cake to install. We'll
see tomorrow or later tonight if it
cools down outside just a bit, really
how well this affair works. Hope I am on
the downhill slide of this problem.

Atleast soon I can think to myself
"Timing, vacuum advance, HEI
distributor... been there, done that"
(and... I really don't wanna go back!)

Nate 75GB (Ping...??? BAD ping, Bad!!!)
Omaha