Jonathan
I basically use a 20/50 multi grade as well which is supplied by Miller Oils in the UK they recommend their 'Classic Sport 20w/50 API SJ/CF, one of my customers in Texas needed to know which was best for his newly supplied/conditioned engine so he used this recommendation & found a near equivalent in USA which is 'Hemmings Classic Oil 20/50 SJ which is semi synthetic also, their web site is '
www.hemmings.com '.
I understand the oil is quite expensive & is shipped to him from the East Coast, I believe good quality oil is essential & well worth investing in, in addition filtration & good flow are essential which is why on my new engine blocks I have a slightly higher rated oil pump, a full flow filter capable of filtering down to 15 microns & I have the pressure relief after the filter, then there are two entry points into the main bearings supplying mains one & two then three, four & five.
To ensure number four main is not starved my new heads have an independent metered supply direct from the filter, so the vertical oil supply pipe only needs to supply the spray of oil to the cross shaft gear.
There is good knowledge around the Club & the owners of the Weller engines, as our engines are used also by the Frazer Nash Special owners they use them probably more competitively as well,at the meeting last year about half attendees were Frazer Nash owners, this means we get a good mix of experience available, sorry it is difficult for some owners to attend but we will do our best to help when needed.
Regards
Robin