When I first got my V8 3.5 10.5:1 compression engine the valve guides were all a bit worn and were letting a fair bit of oil in to the combustion chambers - not a good thing. I did a fair bit of reading up and found there were numerous different heads available, perhaps not too surprising when you think how long this engine has been in production and how many people have used it. Generally speaking they have got better and better over the years with the very latest ones having bigger valves, better port shaping, hardened seats, seals on both inlet and outlet and wasted valve stems. The combustion chamber size has also been decreased from the 36cc of the early units to something like 29cc of the later ones. You have to watch you don't go too high on the compression ratio as that will give pre ignition or pinking so if using a later head on early pistons you must use composite gaskets, which are thicker than the thin steel ones used in earlier applications.
I had already gone for later heads - ERC0216 units that I thought had valve stem seals fitted, I was wrong, I think they just have o rings on the inlets, they certainly have the larger valves and 36cc chambers. They are much better flowing than the original 3.5 litre ones but still not the best you can get if you want revs and power.
I hadn't intended to do much with the car as we were moving house and a guy over at Coningsby had a 4 litre engine on facebook for the ridiculously cheap sum of just 150 quid - I was very happy to pay that just for the heads. So I went and got it, took it to bits and sold some of the bits I didn't need to cover the cost. I still have loads of bits left, including the ACE pump which can go for about 300 quid as they are really hard to find. I will sell mine for half that so someone will get a bargain and I will have the cash to buy the gasket and seal set that I will need.
Anyhoo, the heads on this engine are HRC2479's and are reckoned to be the best ones - big valves, hardened seats, wasted inlet and outlet, seals on both, 29cc chambers, very good gas flow, which can be further improved with very minor reshaping of the ports. I don't know how many horses this will release but it can only help matters, should be really good for emissions too. My car only has to be tested for visible smoke as the engine dates from 1973 and anything pre 75 is visible only with no metered test being required. Doesn't do any harm to do the right thing though and make it as good as it can be.
They were filthy and have taken a lot of cleaning, the valves have been removed and ground in, everything has been cleaned, it all looks in much better nick than the stuff they will be replacing, I am told these ones had only done 90k miles but to be fair whoever owned it really should have done more frequent oil changes. It's taking many hours of scrubbing and fettling to get them to the point where I am happy to fit them to the car, they should be a worthwhile upgrade though.
I am hoping that with the composite gaskets fitted the compression ratio will still be about 10 to 1 and that with a small retardation of the ignition timing it should run well without any pinking caused by pre ignition. If I ever go the turbo route I will need to rethink things as the compression ratio will then be way too high, that's nothing to worry about before IVA though.
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