Distributor off a tooth

[Lawrence S.]

Re: Distributor off a tooth

Admitingly I have not blipped the throttle up above 4K but will do so.

[Lawrence S.]

Re: Distributor off a tooth

Admitingly I have not blipped the throttle up above 4K but will do so.

FYI the distributor is correct for the car. Is dated correct and was in the car 10 years ago when I restored it. At that time the car was just an old unrestored car with a bad paint job. However I have no idea about the base plate, picture attached. The distributor had very little play and new shims installed. I had the distributor refurbished a few years ago.

[Lawrence S.]

Re: Distributor off a tooth

Now that my distributor gear is installed correctly car running so much better I have started to fine tune the timing map. I have the lightest springs installed in the distributor (Mr. Gasket 928G), and the vacuum canister plugged in to full manifold vacuum. (FYI, I have the B28 can due to the cam and have achieved the 2" rule) I started at 15* initial with the car idling at 750 - 800 rpms. With vacuum attached to canister I had 36* at 800 rpms. With no spark knocking I then went to 17* initial with 36* at 3K plus rpms vacuum unplugged. With vacuum advance plugged in I was at 39* at 1000 RPM's. Blipping the throttle it appeared to get to 53* but am by myself so this is not 100% confirmed. I then moved the initial up to 19* at 750 -800 rpms, 38* at 3K plus rpms canister unplugged to vacuum, 39* at 1000 rpms with vacuum plugged to canister. Blipping the throttle appeared to get to 55* total timing. The car is not spark knocking, I have put the car in 4th gear going up a grade low speed giving it gas trying to get it to knock and it still will not knock. I have noticed that as I have progressed up the timing curve the low speed torque has increased. The chugging problem that I had before has all gone away now. I can cruise in 4th gear at 1500 rpms with no chugging. Go around corners in 2nd gear at 1200 rpms with no chugging. I guess I can add two more degrees to the initial until I get to spark knocking but I feel like I am at the edge now and the car is running very well. Don't want to press my luck. I am burning 93 octane fuel. Any thoughts or comments I would love to hear them.

Lawrence

[Duke W.]

Re: Distributor off a tooth

Go back and read post #15. Until you determine the centrifugal start and stop points and total centrifugal advance, you're wasting your time and mine. That's the FIRST THING YOU DO WHEN RECORDING THE SPARK ADVANCE MAP!

Get a helper to work the throttle and record the data while you run the timing light.

Duke

[Lawrence S.]

Re: Distributor off a tooth

Duke when I blipped the throttle it appeared that I was getting more advance from say 3K rpms. That is what I posted...55*. Not sure how to get the end point of the centrifugal? Help me out here please. As always thanks!

[Duke W.]

Re: Distributor off a tooth

You determine the centrifugal curve with the VAC signal line disconnected and plugged.

Set idle speed at about 1500 and then reduce it while watching movement of the notch on the balancer. When it stops moving that's the centrifugal start point. Then you increase revs until it stops moving. That's the stop point. On an OE L-79 distributor that would be about 5100, but lower if lighter springs are installed.

Now go back and take readings starting at 1000 in 500 rev increments to to at least 500 above the stop point. Then blip the throttle to at least 5000 to verify that there is no more advance. Finally, rev the engine to about 500 revs above the stop point and set the timing in the range of 36-40, and I suggest about 39 as a start point.

To make things easy you can adjust timing by adjusting the dwell angel. A one degree increase in dwell should increase timing by about two degrees and vice versa, and the final dwell number should be in the range of 28-32. Test for dwell variation by revving the engine up to at least 5000. Variation should not exceed two degrees.

Once total WOT advance is set as above you can reduce idle speed until the balancer notch stop moving to determine initial timing for reference. If the engine stalls before the notch stops moving, tie up the centrifugal mechanism with a rubber band and try again.

Now connect the VAC and read total idle advance at your normal idle speed after goiing through the idle speed/mixture adjustment procedure in the service manual. Then, If you want, increase revs to above the centrifugal start point to read total potential part throttle advance for reference.

There is a wide range of acceptable total idle and part throttle advance, depending on engine configuration as I discussed in the San Diego tuning seminar, and you just want to verify that they are in the ballpark. Record all your data for future reference.

Duke

[Marco H.]

Re: Distributor off a tooth

I would like to add another thought:
On every engine rebuild/restoration, I index the balancer with a piston-stop-tool, to verify that the timing mark on it actually is in line with the "0" mark on the timing tab, indicating TDC. Too many have been off by several degrees (even new "restoration parts"). To set and check the timing, I will use the advance feature on the timing light, which keeps the balancer at zero and I can read the timing on my advance dial. that will also eliminate any potential discrepancies with the timing tab.

Marco