Nothing like my current head, I didn't measure the valves yesterday before I took it to the machine shop to get cleaned up, but I'd say the valves are 1-2mm oversize. The HKS head also has stock buckets, retainers and collets and just has better springs and the HKS cams which I think have about 8.1mm of lift. My new race head has shimless buckets, PSI valve springs ($980 worth) Titanium retainers and ferrea collets, 4mm oversize valves and over 10mm of lift on the cams. We cut 2 separate 1G heads up, of of them from one end to the other through the centre to ave a look at the cooling system and where the water jackets were in relation to the port, and the other we cut sideways through the ports to have a look at the shape and see where we could fiddle.
The head on my new engine is where 90% of my money and development went, it is after all the most important aspect in making power. We even worked out port velocity and runner diam and what port diam we needed to make peak power at 95-9800rpm with no dry ice and over 10 with dry ice, and coincidentally, it makes peak at 9600The difference in port flow has been huge, talking purely in hp terms, the stock 1G head flows about 260 superflow hp, my old head with about as much porting as we could do with stock valves had 298 superflow hp, and my new head has 366
I think its about 231cfm@28" for those that know the figures, and keeping that in mind, thats about as much as a RB26 head with a 3 angle valve seat and some minor bowl work, which in my eyes is pretty damn good!!
I'd say this HKS head flows around the 300-305 superflow hp, better than the head I had on my 9 sec engine, but not anything like my current head. I'll prob get a port tested just for interests sake though
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