The reason I asked, Initial timing can be set higher with a lower compression engine.

I have a 1965 327 with 1966 462 heads. I have my initial timing set a 0°. I have a new vacuum advance canister that advances the timing 14°. The distributor adds another 20° for a total of 34° degrees of timing. The car runs fantastic!

At 4° initial timing, I can just start to sense the starter resisting when I start the car. At 8° initial I get the kick back from the starter plus lots of pinging under acceleration.

 

So your vac can appears to be adding in 19°... or maybe it's not:

• Are you sure your mechanical weights are not coming into play at 950rpm?
• Have you tried lowering your idle closer to 700-800 and rechecking the timing?

 

19 degrees sounds like an awful lot of timing from vacuum. The symptom you describe could be trailer-hitching. from too much timing.
IIWU I would buy a vacuum Limiter device from Lars, and limit your vacuum can to around 10-12 degrees advance.

 

I'm not 100% but I put in the modified/lower tension springs, so I'd assume so. Honestly I was happy the car was running good so I didn't even want to touch the idle haha. I think I could definitely lower it though.&

I'll get the car warmed up and double check it to make sure I'm not getting an incorrect number but Im pretty sure that's where we were at.

 

you are getting there.
I would shoot for springs that will hold timing until @825 rpm then add timing till 3k rpm where no more timing is added.
so, 12-14 deg base time below 825 rpm then 825 starts to add timing a little until 3000 rpm. this timing should max at 24 so at 3000 rpm you have 36 to 38.
12/14 base plus 24/26 centrifugal for total of 36/38 a 3k rpm.
vacuum dist pod should add @ 14 deg

good luck

 

It’s very interesting reading about timing here in the C3 forum. I’m very new to this board and have been a dedicated Mopar guy for the past 20 years, mostly drag racing.

Allowing timing to exceed 34°- 38° is foreign to me with a performance engine.

Under hard acceleration, “Drag Racing”, WOT (wide open throttle), the vacuum advance canister does not function, there’s not a strong enough vacuum signal to pull the diaphragm.

In a most recent street/strip car I built, 70% strip, 30% street (car shows & cruise nights) incorporated all aspects of timing to make the car fun and not exceed 34° degrees of timing.

The motor was a 1972 440, low compression truck motor.
I used the smaller combustion chamber E-Street heads to increase compression. The camshaft was designed to work with the heads and low compression.
Compression ended up being 8.8:1, the cam specs were 499 lift, 236 duration at @.50.

The newer Mopar Performance distributors are set up with 22° mechanical advance from the factory. This motor liked timing. Understanding the golden rule in the Mopar camp, 38° total timing for cast iron heads, 34° total timing for aluminum heads, my initial timing had to be set at 12°. The motor hated it.
Exhaust temperatures were extremely high, the motor ran hot, plus the motor was sluggish.
I advanced the initial timing to 16° not to exceed 38°, the motor cooled down a bit, but performance was not what I expected. No fun seat of the pants feel.




I then proceeded to find out what timing set up made the motor run its best not exceeding
34° total timing with the aluminum heads. The motor had a 10” stall converter (3400 rpm) with a 3.91:1 rear end.

I first purchased a limiting device to limit mechanical advance in the distributor . I was then able to see what the best setting for initial timing was. 22° initial timing was the best setting. With the camshaft being used, I achieved 12 in. of vacuum on the vacuum gauge. RPMs were at 700, transmission in drive with car secured in place.
I then set my mechanical advance limiting device not to exceed 12° degrees of timing, for
a total of 34° degrees of timing.
The next step was to add vacuum advance. The Mopar performance vacuum advance canisters are adjustable. I added 8° degrees of timing with vacuum advance which brought my timing up to 30° degrees with 900 RPM @ idle, with an increased vacuum signal. The motor made the torque I expected when cruising around.

When at the drag strip, the vacuum advance doesn’t matter because the vacuum signal goes down under hard acceleration, maybe 3800 RPM and higher plus the distributor keeps perfect timing.

With the distributors mechanical advance limited to 34°, initial timing plus vacuum advance made the car fun when cruising around town.

Set up, 440 (low compression motor)
22° initial
Mechanical advance limited to 12°
Vacuum advanced adjusted to allow 8° (30°)
@ WOT timing is at 34°.

To start an engine with 14-22 degrees of initial timing, the engine must have between 8.5:1 to 9.5:1

As the compression ratio increases initial timing needs to come down depending on your cams duration.

“If the engine has 9.6:1 to 10:1 static compression ratio, 10-13 degrees initial advance would be correct. More initial advance with 9.6:1 to 10:1 SCR with a short (224 deg.) duration camshaft, the engine would be cranking against the ignited mixture and would be difficult to start”. (Quote from a different message board).

The 327 in the “68” C3 (10.5:1 compression)
I recently purchased, timing had me puzzled. When I checked the timing for the first time with my timing light the initial timing was at 0° degrees, but I had an idle issue, could not adjust below 1100 RPM. The vacuum advance was adding 21°. With the mechanical advance I was at 42° at 3000 RPM, not good.

I ordered a replacement vacuum advance canister. After replacing the vacuum advance canister, the vacuum advance did not exceed 14°. The old diaphragm was weak allowing too much advance at idle.

68 Vette set up (1965 327, 462 heads 10.5:1)-
0° initial
Mechanical advance 20°
Vacuum advance 14° (idles @ 875 RPM)

No pinging, runs very cool, temperature stays around 180°. Extremely responsive. I’m never really exceeding 3000 RPMs at 70 MPH with 3.31 gears (3.73 gears, 3300 RPM) timing would be right at 34° degrees.

 

Get an adjustable can or stop and limit the vac advance to 12 degrees no matter what.

Jebby