Big Valve head?

[klrskies]

Does anyone have information on the use of larger diameter valves installed in an M20 "i" head?

[rs4pro3]

One option is M30 valves, they are just a tad bit larger, but will require the m20 valve guides removed, and the larger m30 guides pressed in.

[trent]

Re: Big Valve head?

Does anyone have information on the use of larger diameter valves installed in an M20 "i" head?

You can contact a number of suppliers to have larger valves made.

Del West is an amazing valve company.

http://www.delwestusa.com/

You can also contact Manley and Ferra(sp?)

[Jand3rson]

One option is M30 valves, they are just a tad bit larger, but will require the m20 valve guides removed, and the larger m30 guides pressed in.

Is this a job that machine shop could easily do?

What kind of gains can be expected? Minimal or fairly noticeable?

Can new M30 valves be purchased as easily as M20 valves?

[rs4pro3]

Yes 325i's use 7mm stems, the m30's use 8mm stems.
m20 exhuast valve is 36mm and m30 is 38mm
m20 intake valve is 42mm and m30 is 46mm
The valve train compents on the m30 are also a little larger, I'm not 100 % positive it would work, but I've got the cylidner head sitting here from my dad's 89(snapped t-belt) that I'm putting new valves in and I tried some of the m30 valve and it looks like the seats line up pretty close, they'd of course have to be ground. The m30 valves are 5mm longer so I don't know if this would cuase any problems with valve lash clearence. Like I said this is just an idea that poped into my head when comparing the 2 heads.

Used m30 valves have no market I tried selling a set with springs for $50 and they never sold.(becuase most want the B35 larger valves)

[trent]

Yes 325i's use 7mm stems, the m30's use 8mm stems.
m20 exhuast valve is 36mm and m30 is 38mm
m20 intake valve is 42mm and m30 is 46mm
The valve train compents on the m30 are also a little larger, I'm not 100 % positive it would work, but I've got the cylidner head sitting here from my dad's 89(snapped t-belt) that I'm putting new valves in and I tried some of the m30 valve and it looks like the seats line up pretty close, they'd of course have to be ground. The m30 valves are 5mm longer so I don't know if this would cuase any problems with valve lash clearence. Like I said this is just an idea that poped into my head when comparing the 2 heads.

Used m30 valves have no market I tried selling a set with springs for $50 and they never sold.(becuase most want the B35 larger valves)

Valve's can easily be cut to the correct length by a competent machine shop.

However, you forget to bring up the point that the larger valves and valve stems also WEIGHT more. The name of the game is to REMOVE weight off the top of the valve -- not add. Therefore, this is why one for true performance gains should have custom valves made (some companies already make them) in the correct stem width and they will also be lighter. :)

[rs4pro3]

Ya true didn't think of that.