Big valves

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Schweg
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Big valves

Post by Schweg » Tue Jun 16, 2020 7:33 am

Not sure this is right place for this, but here goes anyone know what the biggest valve you can put in a stock casting head is? I’m looking to replace seats as well.

Thanks


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66brm
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Re: Big valves

Post by 66brm » Tue Jun 16, 2020 5:46 pm

Depends on bore, a 42*37.5 will fit a 94 but not 85.5. To go larger with out issues irt longevity the guides need to be spread

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Schweg
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Re: Big valves

Post by Schweg » Tue Jun 16, 2020 5:59 pm

Thanks!

So is it worth trying to fit larger calves in a stock head or just buy different castings?

That I guess is the second part of my question hearing that guides need to be moved.

Schweg

66brm
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Re: Big valves

Post by 66brm » Wed Jun 17, 2020 1:29 am

How big are you looking to go? 90% of street engines have no need to go larger than 42mm intakes unless they see a lot of strip time. Add boost and the need for a larger valve is also reduced.

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Schweg
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Re: Big valves

Post by Schweg » Wed Jun 17, 2020 5:16 am

I’m really just trying to learn. I’m thinking a 40mm/37mm set up would be nice but as hard as I look I can’t seem to find out if there is enough material to do that.

I have a line on some used stock casting pretty much free that I am thinking about trying to build into 1915 turbo heads with a home port and polish. There is a local shop that will cut seats and do so guides for around $200.


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Schweg

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FJCamper
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Re: Big valves

Post by FJCamper » Wed Jun 17, 2020 5:25 pm

40x37 with moderate headwork will support up to 150hp no problem with the right cam and intakes if you keep it down to 6000-6500 range.

We usually run this valve combo on our Type 1 racing engines (LeMons endurance races) with great success. Once in a while we'll get a set of heads with 42mm intakes and bolt them on with our same usual carbs cams, etc., but notice no significent power difference.

FJC

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Schweg
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Re: Big valves

Post by Schweg » Wed Jun 17, 2020 5:52 pm

Fj,

Thanks for the reply.

Are you doing that with a stock casting?

Schweg


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FJCamper
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Re: Big valves

Post by FJCamper » Wed Jun 17, 2020 11:39 pm

044 casting.

Good luck.

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