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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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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

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

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.

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.


Thanks

Schweg

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

Fj,

Thanks for the reply.

Are you doing that with a stock casting?

Schweg


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044 casting.

Good luck.