u need to get the points dwell right first, Is this the type u can adjust running with an Allen key?
u will need to find the spec and check with an accurate dwell metre first, then adjust the timing 7 degrees should be close but you need to check the total advance sbc usually around 36 degrees total all in by about 2800 rpm depending on cam etc, check it does not advance to far? a broken andvance spring will give u this trouble, u need to fix the pining don't run it like this or death will occur.
pete.

Yes, there's a window on the distributor to adjust points externally. Omitted to say the engine is out of a 1965 Impala & it's 336 degrees total all in by about 2800 rpm�6 degrees total all in by about 2800 rpm�0 hp, 10.5 compression ratio, whereas the Holden 327 was 8.75.
Holden HK v8 distributor specs say maximum centrifugal advance is 28 @4200 rpm & initial timing is 4 btdc. I don't understand how to get total advance of 36 @2800 rpm when it increases until 4200.
Sounds like it could be a problem with weighs, rather than vac advance?
Thanks for the help.

The numbers you are quoting from the HK manual are for a 307 or 327, which are a much lower compression ratio. With your compression ratio in my opinion a more appropriate first guess would be the 10.25:1 350 manual engine numbers, which specify a 2 degree advance initial. Assuming its a Delco Remy 1111150 distributor, it should have centrifugal advance of 0 degrees at 900 RPM, 15 degrees at 2000RPM and 28 degrees at 4200RPM.
The vacuum advance contributes a further 15 degrees at full vacuum. The vacuum advance only contributes any advance when there is vacuum, which is at idle and very light throttle openings. An aggressive camshaft may even reduce the amount of vacuum available at idle to the point that the vacuum advance is inoperative. All this advance at idle is necessary as the lean mixtures at idle take longer to ignite, hence the spark is initiated earlier. The mixture is richer at higher amounts of throttle when the carb butterflies are open, the main jets are contributing fuel and maybe the accelerator pump too and these conditions coincide with less vacuum and less vacuum advance.

You should be able to get some idea of the distributor mechanical advance condition at 2000RPM, where the advance should be initial + 15 degrees, with the vacuum advance disconnected and the line plugged on the vacuum side. If its much more than this, it is likely the spring(s) are weak or broken. An auto electrician with a distributor machine will be able to confirm this for you in a few minutes.
If the points are in reasonable shape setting the gap to the aforementioned 19 thou should get the dwell close enough for now.
A couple of other things:-
1/Some dwell meters have only a 4 and 6 cylinder scales, and require you to divide the 4 cylinder scale by two for 8 cylinder engines. 16 and 30 degrees are roughly 2:1. Didn't make an error here by any chance?
2/Did you check the timing marks on the harmonic balancer for agreement with TDC on number 1? The outer rings have been known to move, which throws all your timing numbers off. It can be done in the car with a piston stop, or less accurately with a $30 USB camera through the spark plug hole and much fluent swearing.

You say the motor was out. Did you rebuild it? If you rebuilt it, did you replace the cam? Is it standard or did you degree it in if non standard? I have a 350 in my HQ and replaced the dizzy with an MSD unit and set the initial timing at 12%. I tried it at 8% and it seemed sluggish. I read around the forums the 7% initial was all about emissions and around 12% initial can improve drivability off idle. I use 12% initial with a total of 34% at 3000rpm. With the MSD, it's all adjustable with springs and collets which at all provided. I use 95 or 98 octane fuel, not for any reason other than I don't trust E10. I didn't want to use the standard dizzy because of the problems you are encountering and to get it converted to electronic cost more than an MSD dizzy with blaster coil.

No, I didn't rebuild it. I replaced the welch plugs and changed over the oil pickup and sump to suit my HT and put in new rocker & sump gaskets then ran it a few times to check it was ok before I put in in the car.
Are there other options for a breakerless dissy or is MSD the best value and is the changeover straightforward? (Looks like they start at under $200 for a MSD streetfire).

Pending Santa giving me an MSD coil, I removed and did a bit of work on the dissy (end play, replaced vac can & earth wire, filed points, replaced capacitor) then installed it to to #1 cylinder firing position. Cleaned and gapped plugs.
Now the engine revs reasonably in Neutral but when in Drive & brake applied, it slowly dies at aroung 800 rpm and the timing light showed the timing retarding from about 18 degrees back to the initial setting of 4.

Compression checked all cylinders with readings of 180 to 195 psi. Does this mean the lash and lift are OK or should I check & adjust these?

Would appreciate any assistance to sort this out, please.