Distributor initial timing 73 L48

[Steve L.]

On an 73 L48, I noticed that in the AIM, there is a mark on the intake manifold and on the distributor housing with a note that they should be aligned. I just wanted to get a response if this is correct?

I've got my rebuild engine on a test stand and initial timed using a test light to 8* BTDC. It runs but not well. It looks like I missed at least one tooth when installing the distributor.

Just as I was going to time it better,both my 40 yr old dwell meter and timing light died at the same time. Gotta get a new set. Meantime, I need to reset the dist. properly.

[Patrick H.]

Re: Distributor initial timing 73 L48

On an 73 L48, I noticed that in the AIM, there is a mark on the intake manifold and on the distributor housing with a note that they should be aligned. I just wanted to get a response if this is correct?
Just as I was going to time it better,both my 40 yr old dwell meter and timing light died at the same time. Gotta get a new set. Meantime, I need to reset the dist. properly.

Yes, this is correct.

Assuming that your distributor and your intake are original to your car you may set the timing in this fashion.
In fact, if you do it you won't even need the timing light. I've done it on a couple of engines - install distributor, line up mark, start engine. You're not good to go!

Patrick

[Steve L.]

Re: Distributor initial timing 73 L48

Thanks,
Dist. and intake are original.
For 73, the service manual says 12*BTDC, but I used to run it at 8*.
So are the marks set for 12 or 8*? I suspect that it is 12*. It used to run like crap at 12* when I picked it up new back in 73.

[Patrick H.]

Re: Distributor initial timing 73 L48

I'm sure that they're set at whatever factory specs were supposed to be.

I'd change it to full time vacuum advance and that will probably make it run much better.

[Joe L.]

Re: Distributor initial timing 73 L48

Thanks,
Dist. and intake are original.
For 73, the service manual says 12*BTDC, but I used to run it at 8*.
So are the marks set for 12 or 8*? I suspect that it is 12*. It used to run like crap at 12* when I picked it up new back in 73.

Steve-----


12 degrees BTDC is the initial advance spec for a 1973 L-48. However, 12 degrees is a lot of initial advance for an L-48. I suspect that spec was the result of the influence of emissions regs more than any other reason.

[Duke W.]

Re: Distributor initial timing 73 L48

12 degrees is a fairly high initial timing setting for an emission controlled engine with ported vacuum advance, but it is far below what is optimum for minimum idle fuel consumption and smoothness.

The antecedent engine is the 327/300 (They both use the same camshaft), and prior to emission control these engines typically called for 8 degrees initial and full vacuum advance of 16 degrees was applied at idle, so total idle timing was 24 degrees.

The fact that the OP says that it runs better at 8 initial rather than 12 indicates to me that there may be some other underlyilng problem - like an improperly assembled and/or installed distributor, which can cause misalignment of the rotor tip and cap tower enough to cause misfires.

Duke