8V Race prepped engine oil 10w40 or 5w40-semi or fully synthetic ?

Hi there,

Im currently using 10w40 semi synthetic oils (and I've tried a few) in a tight tolerance solid lifter 8V engine built entirely for race use some years ago by TSR.

Its only done 16000 miles since then, was not raced and hasn't been used for 10 years so the condition is pretty much as new. Cold start has some  cam noise which concerns me and rather high oil pressure readings, all is fine once warm so I was thinking of trying 5w40 semi synthetic.

The trouble is if I remember correctly I was warned by Tim Styles at TSR (the 90s god of all things Golf) not to use fully synthetic and to keep to the manufacturers recommendation of 10w40, im kind of doubting this now, what do you reckon guys ?

Non hydraulic tappets/lifters remember, early engines and rare these days !

Im thinking a 5w40 semi synthetic race type oil by Fuchs for example

Cheers

Eliot