Distributor and ignition advance

I’m trying to set my ignition timing on 1960 XK150 3.8L following my engine rebuild (new cylinder liners, pistons, rings, bearings) I confirmed the TDC marks on the damper are correct.
I have an “in distributor” Powerspark (UK) electronic ignition which works very well but means having to use a timing light; at 500rpm idle I have 8deg BTDC which seems about right but with vaccum plugged I’m only getting about 22deg advance at 3K RPM, I would have expected maybe 32+deg.
My DMBZ6A distributor is set up exactly like the picture (courtesy “Tapped”) with a limit stop on the 13deg mark.distributor1
Anyone have any ideas on why this is?

depends if you are running chevron super gasoline or a crummy inconsistant blend, are you in the west?

why do you bother with limiter?

I’m in BC, using the “expensive” higher octane fuel, no sound of any pinging which isn’t surprising since its maxing out at only 22deg advance on 8:1 CR.
The distributor is set up how I received the car, I could remove the stop pin collar which would allow some additional travel.
Or I could reverse the shaft to the 25deg setting, however, I believe the distributor runs at half crankshaft speed so that might give me way too much advance.

I’m in BC to and have a 140mc. Shouldn’t you add the static so you have 30 now? These cars run well at 34 all in, so maybe just add degrees through static timing? On my C Type head I resorted to a 123 Tune dissy to get the best curve and top out at 34. I have a 4.2L that likes 38 all in. I use 94 octane.

we are all on the same page. i have found it all to be quite forgiving if the distributer is worn etc. on gasoline 94 plus - i have had some problems with mok…k 94 but put that don to poor blending and cheating but the chevr…n is really good for 94+ you have to put in a lot of 110 to make it much better especially on over run, on cng where you run a lot of advance better more accurate and higher voltage was essential. but i never needed a scope etc. a good distributer shop is a definite asset and worth the minor expense one in poco good. ymmv john

Thanks for the replies and to close this thread out, I found that the distributor installed in my car had a collar on the stop pin that limited the centrifugal advance to only about 7deg (14deg at crank), when I removed the collar the centrifugal advance now goes to 13deg (26deg at crank) when added to the initial advance of 8deg plus 26deg=34deg at crank which seems correct. I believe the distributor was originally out of a 9:1CR engine, hence the lesser advance; all is well now.

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