1972 Coronet w/ Slant 6 timing questions

Hi There:

I just bought a '72 Coronet with a 225 automatic and it seems to work
pretty well aside from being a bit pokey in the acceleration
department. My question is this - where does the distributor vacuum
advance connect to - is it ported, or does it get connected to manifold
vacuum like it is now? It still has points ignition, and a one barrel
Carter Carburetor.

The engine is supposedly out of a 1968 truck, and was an engine used at
a vocational college here for students to rebuild.

Thanks for any advice!

 

On early to mid-1960 225's, the vacuum advance would connect to a port
on the base of the carburator. When emission control equipment started
to arrive later in the decade, that most likely changed.

-Kirk Matheson

 

I think it comes off a small port on the intake manifold. If it's not
there, maybe it fell off and is causing a (small) vacuum leak which
will affect performance.

There are a few things you should measure on this engine if you have
the inclination.

1) If the engine really did come from a '68 truck, then it probably
does not have hydraulic tappets - which means the rocker arms
are manually adjusted (valve lift) while running (interesting
experience).

2) set the idle RPM to 550 and connect a vacuum gage to the
intake manifold. Leave the vacuum line connected to the
distributor. Rotate the distributor so that the vacuum
reads the highest value (which is dependent on your altitude
but at sea level if the engine has good valves/seals/rings
you should be able to pull 20 to 23 inches of mercury. Once
you've found the max setting, lock down the distributor.
(this setting may not give you the best emissions but it
should give you the best milage and performance).

3) If you're so inclined, get new plugs and points/condenser
and set the distributor up properly (dwell). Gap the plugs
before you put them in. Maybe new primary coil and wires,
fuel and air filter. If you do any of this, do it before
performing step 2.

4) If you're really keen, you can get a carb kit and take the
Carter apart. Change needle valve, check the floats, replace
the gaskets, etc. Note that the upper and lower surface of
the air horn are prone to warping and don't always seal
nicely. I've sanded mine down to insure a good seal. Be
carefull that you don't turn down the long screws too
tight or you'll warp the air horn. If your float and needle
assembly isin't set correctly you'll have gasoline gushing
all over the engine so be ready to shut it down the first
time.

5) Get a compression guage and check the cylinder compression
values. I think that you should get values of 100 psi
(+/- 20) - the higher the better, and the more even or
similar the better (although I wouldn't be happy with all
6 giving 80 psi vs 120 psi.

6) perform a leak-down test (crank the engine so that the
valves for each cylinder are closed and then with
compressed air give the cylinder a charge and then
watch how quickly the charge bleeds away. This will give
you some indication of the health of the valve seals,
rings, valve seats, etc.

Oh man looking back (15 years ago) boy did I spend too much time
working on my slant-6. Was nice when I had the time...

 

The vacuum advance hose gets connected to the one and only
appropriate-diameter hose nipple on the passenger side of the carb. This
is ported vacuum.

Head over to www.slantsix.org for quality advice on this car.

DS

 

Base of the carb. You’ll know which one it is by pulling off the plug
and checking for vacuum at idle. If there is no vacuum at idle gently
hit the gas and see if vacuum presents itself. If so thats the
baby...... Chrysler used timed advance..

 

Bzzt.

Chrysler used ported vacuum *or* manifold vacuum for spark advance,
depending on year, engine, transmission and emissions package. In either
case, the spark advance hose nipple is in the same place on the
carburetor.