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Re: L16 ex valves
No life (a.k.a. DattoMaster)
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bore notching for the larger exhaust valve is usually required.

Posted on: 2016/5/19 6:30
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Re: L16 ex valves
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I read somewhere that Aslong as the diameter of the two valves added together is smaller than the bore it should be fine. Say the valves are 69 or 70. Thats well under the bore size of an A15.

Posted on: 2016/5/19 6:50
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Re: L16 ex valves
No life (a.k.a. DattoMaster)
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The problem with the A series [well not really a problem but rather a design feature] is that the inlet is more centered in the bore and the exhaust is off to one side. Check your clearances during the dummy assembly phase of your build.

Posted on: 2016/5/19 7:13
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Re: L16 ex valves
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Yeah I think I'll have too. So you think going the 38mm inlet rather than the 37 is a good idea or should I leave it at 37/33?

Posted on: 2016/5/19 7:19
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Re: L16 ex valves
No life (a.k.a. DattoMaster)
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From memory I used L series valves and cut them down
Redid the collet groove and used lash caps on top to stop mushrooming
38mm inlets and 33mm exhausts

Posted on: 2016/5/19 11:06
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Re: L16 ex valves
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Did you have to notch the bore for clearance?

Posted on: 2016/5/19 11:19
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Re: L16 ex valves
No life (a.k.a. DattoMaster)
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Yeah you defo need lash caps.
I ran Manly lash caps on my 42mm L20B inlet valves on my last A15.

Posted on: 2016/5/20 10:22
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Re: L16 ex valves
No life (a.k.a. DattoMaster)
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Lash caps also correct the valve geometry too. With big lift the rocker arm sweep goes past what is really happy.

Posted on: 2016/5/20 10:23
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Re: L16 ex valves
No life (a.k.a. DattoMaster)
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37mm inlets and 33mm exhaust valves flow plenty for many high hp applications

1mm larger for the inlet is not worth the cost/work best go 38-42mm inlets at least

Posted on: 2016/5/21 7:25
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Re: L16 ex valves
No life (a.k.a. DattoMaster)
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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.

Posted on: 2016/5/27 15:02
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