M43 valves in M20 head

[abit]

hey, does someone tried to use m43 valves in m20 head?
going to use m43 intake valves in my engine, but I have some questions
m43 valves is ~2mm taller than m20 valves in full lenght and also from big end to valve cotter grooves.
so, what should I do to keep stock valvespring setup, put ~2mm spacer behind head and lower spring pad?

M43 left, M20 right


as you can see, M43 valves looks better designed, slim, and they are ~13 grams lighter than m20 valves


outside look

[abit]

hmmm....


the thing is that I know that one guy is already using them, and he just grinded 1mm off the valve stem. But the thing is, using these valves, valve spring would be less compressed in closed and other positions, so I thought that I should put something under valve spring (compensate those 2mm) to keep it like stock, right?

[Bullhead]

If your going to keep the same spring psi then you need to space it. Grinding the top would only give clearance and wouldn't change the location of the keepers. I have no idea about putting those valves in the m20 head but the only other option would be to weld the top of the valve up then turn it back down and turn the grooves back in for the keepers.

[IronFreak]

Your theory on the spring is probably right. You could probably just go wit ha double performance spring and not even worry about that. I don't know off hand but rockers have eccentrics so you might be able to shave a touch off the valve and adjust the rest out with the eccentric.

[SkiFree]

An effort in diminishing returns. And your M20 valve sample is strange, something not quite kosher.

[mr2peak]

Sub'd

[raudonis]

Just of curiosity, what is m43 valve diameter?

[abit]

Just of curiosity, what is m43 valve diameter?

same as m20, 7mm. big end diameters also are the same. only difference is lenght.

[raudonis]

But is it really worth it just for reduced weight? Real gains come from going to 44mm intake valves, most high power m20s have it. Rama from Australia (e21jps) used some cheap aftermarket Ford valves turned inside lathe to appropriate measurements + single groove Nissan retainers and that's it - nothing fancy:

http://www.e30tech.com/forum/showthread.php?t=117701

[abit]

of course, putting oversize valves is another level in power gain, and more higher costs :D

but this could be really low cost upgrade.
not just weight, but also that lover end is slimer than m20 valve, so when valve is open, there should be more clearance from valve to valve seat = more air/fuel can get thru, right?

[abit]

just wondering, If I put some spacer between head and lower spring pad, it could affect valve rotating (I mean I t would not rotate anymore on high rpms)? Or this lower spring pad doesn't rotate anyway, just spring and upper retainer?

[abit]

hey guys, that's all, no more suggestions? :D

If I will decide to put spacer under lower spring pad, I should make it from soft (aluminum) or hard metal? (considering valve rotating etc)

also talked with the owner of car, who already put those in some while ago, he said that he just shortened valve top about 1mm and that's all, no fucking around with spring ratios etc. But does this loosen spring, couldn't affect valve float? Engine limiter is on 7k so, no really high revs

[Ether-D]

I really like any idea that takes parts off other, less desirable cars, and makes em fit our cars.

I'd say definitely space the springs to keep the tension the same. It seems easy enough. Nobody likes broken rockers.

[IronFreak]

I think 7000rpms would create some serious havoc on soft metals, why most you your valve train is hardened.

[abit]

mmm, yeah, I thought about that too, that soft spacer can be wearing out in short time

so, I should take some stainless steel spacers and make them polished finish - slippery, so valves would keep rotating on high rpms and so on?
....and hope that these spacers won't make grits in my oiling system :D