Working out a head gasket failure

[Andy Bennett]

Well. I had a run around the block yesterday and all seemed OK.
We had a trip out today to the local village show. 12 miles each way. It's hillier than my test drive and with 2 of us plus lunch/stove/chairs etc we were fully loaded.
it is more downhill on the way and uphill on the home run. On the way home in particular she was a little rumbly under load (but fine on top speed, I didn 't push but 30 to 35 no problrems) and pinking under load (well that is what it sounded like to me, either that or an extremely loud tappet).

All I did was change the gasket and head, didn't touch the timing.
I will have a little play with timing to see if I can fix, but noting that on my cold tests the compression appeared c30% better than when last tested (c90 to c120) am I right in my understanding that in principle increasing the compression means that I need to retard the ingition a little to regain balance as this would work with my practical experience?
Also noting I am using a bosch distributor so no manual adjustment.

Thanks
Andy