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| Re: L16 ex valves |
Subject: Re: L16 ex valves
by jmac on 2016/5/27 15:02:06
It'll also pay dividends to talk to whoever is porting the head. When they take into account the size of the engine, the rpm range/power levels and what they are going to be doing porting wise, it will ultimately determine ideal valve sizes, and if they have experience with this head (and hopefully they do) they'll also take into account and bore/valve shrouding/relieving issues and make the valve size choice and any clearancing work requirements to ensure it all works harmoniously. The best head porters will either have the runs on the board to know the score, or will flow test with a 'dummy' cylinder of your bore size under the head in the same offset/alignment as the datsun bore would be in real life. This is critical to flow testing (if you want to see that at its 'worst' try the old holden 6, the valves are centred front to back, but the valves are closer to one side of the bore left to right than the other, and the flow almost has to do a 180 (well not quite) turn to go back and then down in to the cylinder, and flow testing without accounting for it is a sure path to inflated results that are never matched if the engine is ever put on a dyno)
As a very very generalised commment about headwork and cam choice, more often than not less is more. if it isn't a full on race engine, go a little conservative, and you'll almost always kick goals with a broader and stronger midrange over peak hp in general. It's even more important on a streeter.
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