VCCA Home Forums TECHNICAL - 1945 AND NEWER 1965-1970 1966 with 327 - Timing solution

I've had tons of problem trying to time my 327 over the past three years.... Finally I broke down and decided to take it to a mechanic (What???!?!) and have him do a tune-up. Expecting this to be a 1 or 2 day effort, I was in for a real surprise.

Within an hour he found a crack in the carburetor base plate. This was causing an ongoing vacuum leak at all speeds. And that has prevented me from finding the SWEET SPOT for the timing.

Now, after 5 weeks in the shop (since I had to ship the carb base plate to Oregon to get it welded), finally I was able to go give it a test drive last week. This is the INCREDIBLE PART.... in order to keep the car running at low and high speeds without any pinging, and with good acceleration, he plugged the vacuum advance!!!?!?! I was blown away. It runs fantastic between 0 and 70 (which is all I could do in the limited space that I had on the freeway). For reference the distributor is now set to 4 degrees advance.

Has anyone else ever run WITHOUT the vacuum advance installed.?

--Bill

I have a 1968 327 with a four barrel carburetor and it runs absolutely fantastic with the vacuum advance connected. Wouldn't think of running it without a vacuum advance. The factory timing for my 327 is 4 degrees advanced. I have it bumped to 8 degrees advanced because of the crappy Ethanol gas and it runs even better at 8 degrees than it did at 4 degrees.

And, the vacuum gauge, in Park at idle, reads a steady 19.

The vacuum advance advances the timing when the engine is not under load. When under load such as during or hill climbing, acceleration the engine vacuum drops and that will cause the "advance" to retard the timing. This would be equal to having the vac, adv. disconnected.
A 1966 327 275 HP engine has a 10.25 compression ratio (350 Hp engine has 11.0 to 1) and if you live close to sea level it will require premimum gas.
They always did run better with the timing advance a few extra degrees whch is true for 95% of engines.
My 1957 283 dual 4 barrel engine I had in my "new" 1957 did not have a vacuum advance but the timing was set at 12 Deg. advanced at idle.

I know this is a very old post but I am just now reading it as I am a new member. So I figure others in my situation may be reading also. I had trouble with my 67 Chevelle over heating in traffic. I had read an article stating that HiPerformance engines do not need vacuum advance so, I did not have it connected. I then later came across an article that stated every street driven vehicle should have the vacuum advance connected and to full manifold vacuum. I reconnected the vacuum advance along with adding a shroud and better fan blade. No more over heating problems! Here is a link to and article from Hot Rod magazine that does a good job explaining why it needs to be connected.

http://www.superchevy.com/how-to/ad...bout-vacuum-advance-and-ignition-timing/