1969 L-46 Distributor Centrifigal Advance

[Steve M.]

Doing a frame off on a 1969 convertible with the 350/350. After having the engine blue printed and balanced the engine runs great. After reading an article by John Hinckley, Mapping Your Advance Curve, Thought I would do this to check out the distributor. In the Chevrolet Chassie Service Manual, They multiple specifications but Nothing for the L-46 with the 1111493 Distributor. Does anyone have the specifications for Centrifuglal Advance C-4732 ? Thanks in Advance for any information.

[Larry M.]

Re: 1969 L-46 Distributor Centrifigal Advance

Steve:

I do not have the specs, but I am certain that someone will post them up. But, you just need to go ahead and map out the advance curve regardless. Most of us (or many of us) can tell from what you determine whether it is adequate or not.

Disconnect vacuum advance and plug it. Start at you idle RPM and initial advance. Then lower the idle RPM and see if the initial advance is further reduced. In some cases (like my 1967 327/350 HP car) my idle RPM is around 900 RPM, but it contains a bit of centrifugal advance. I must go down to 550 RPM to really see what the initial advance is set at.

Then go to 1000 RPM and get read your advance. Do this in 500 RPM increments up to 5000 RPM or until there is no further advance being obtained. It is best to have a helper in the car to work the accelerator pedal for you. I also recommend safety goggles to keep dust and dirt out of your eyes at RPM above 3000.

Then return to idle, note the RPM and reconnect the vacuum advance. The RPM will likely increase. Then adjust the RPM back to the initial RPM you had before vacuum advance was added, and then read the new advance number. That will be your vacuum advance contribution (without any change due to centrifugal advance). If you use a Mighty-Vac instead of engine vacuum to work the vacuum advance unit, you can use the timing light to see exactly the vacuum when the vacuum advance comes in and when it is all in.

Having a dial back timing light is best, but you can do all this with a regular timing light if you degree your balancer with masking tape and a marker.

Larry

[Joe L.]

Re: 1969 L-46 Distributor Centrifigal Advance

Doing a frame off on a 1969 convertible with the 350/350. After having the engine blue printed and balanced the engine runs great. After reading an article by John Hinckley, Mapping Your Advance Curve, Thought I would do this to check out the distributor. In the Chevrolet Chassie Service Manual, They multiple specifications but Nothing for the L-46 with the 1111493 Distributor. Does anyone have the specifications for Centrifuglal Advance C-4732 ? Thanks in Advance for any information.

Steve-------


This is all I have on it:

0 degrees @ 500 RPM

5 degrees @ 850 RPM

13 degrees @ 2,500 RPM (full advance)

[Larry M.]

Re: 1969 L-46 Distributor Centrifigal Advance

Steve-------


This is all I have on it:

0 degrees @ 500 RPM

5 degrees @ 850 RPM

13 degrees @ 2,500 RPM (full advance)

I am assuming this is distributor degrees in distributor RPM. OP should double the numbers for crank degrees at crank RPM.

Larry

[Lawrence M.]

Re: 1969 L-46 Distributor Centrifigal Advance

Steve, you need the 1970 Chassis Service Manual for 1969 Corvette distributor specs. On page 17 of the Specifications section the L-46 1111493 centrifugal advance is :
0 @ 1000
10 @ 1700
26 @ 5000

[Richard P.]

Re: 1969 L-46 Distributor Centrifigal Advance

No mention as to whether or not the Distributor is original to the Car or if it has been rebuilt using a new Shaft and Weights. GM made lots of different Curves depending on the Engine and Year mostly early Emissions related. In our world today, if You buy a new Shaft and Weights, You can get High Performance or Low Performance Curves and nothing in between. This doesn't mean You still can't change the Curve by grinding in the right places and changing Springs. I recently rebuilt a 63 Tach Drive and learned this. Chicago Corvette Supply has USA made parts.