Grease Monkey wrote:Hi Andy, welcome to world of classic car ownership, enjoy it!
I'm sure the Daimler V8 had aluminium heads which will have valve seat inserts fitted & these should be ok to run with unleaded, but I may be corrected!
This is absolutely correct. I know that some aluminium heads have reputedly been built with seats that are softer than those which are a match for the coefficient of expansion of the surrounding aluminium but - taking an example: The seat inserts in the Rover V8 heads - although some specialists reckon that only those built after a certain time are suitable - were all made from precisely the same tube stock and, in one of the labs at work (metallurgy) where the clean-looking chaps and chappesses with the white coats on are to be found, analyses have shown time and again that there's no difference between the seats in any two sample heads regardless of their years.
A couple of years ago, when I was still full time and managed to do my own experimenting with the fancy test gear after hours, similar comparisons were made between inserts from a variety of older, aluminium headed engines and among us we never yet found any case where the inserts were too soft. Valve differences yes, but the worst that we found with those would be burned seating areas on the heads of those exhaust valves so affected. That was more likely to be a result of weak mixture or similar issues and besides, valves are a whole lot cheaper than having inserts fitted which is quite unnecessary in the Daimler Hemis, the Rootes OHV engines in cases where they had the ali head, Jag XK engines, 2CV flat twins, all OHV Reliant engines from the 600 right through to the 850, Ricardo slant fours and the V8 version from Saab 99s, Dolomites, Stags, TR7s etc. O-series engines of all ages and capacities and many, many more. If the seat inserts had been too soft, they'd have fallen out on a frequent basis and those engines which did
sometimes suffer from that fault, such as some (twin port especially) VW flat fours and earliest Imp units have either tried to eat their own valve seat inserts and been repaired or replaced since, or those were only rogue examples whose seats were taken from the wrong stock at the assembly stage.
I've covered over 200,000 miles in Dolomites, a further 200k or so in Reliants, 80k in a variety of others such as a Princess made the week after the O-series became the standard fitment, a VW1500 automatic, a variety of Renaults and Volvos with the Alloy-headed OHV "Sierra" series of engines and few of those cars had an easy life, none ever suffered from seat recession. By comparison, I wrecked the cast iron head of a miniMETRO on unleaded in under 4,000 miles
. It was supposed to have come with a converted head and clearly hadn't.
Yes, your Daimler Hemi is fine for modern fuel, but use
Super unleaded in that one if it pinks as I'm told they don't like the cheaper Premium stuff as much, that obviously being about compression ratio and ignition characteristics and nothing to do with seat to head metallurgical interfaces.
