3.4l iron head valve size question...

[oxrabidus]

whats the aboslute biggest valve size that could be used on the iron heads? 1.94/1.5 valves will fit within the bore of the 3.4l, but could you use them on the heads?

[SappySE107]

The real question is if going larger valves would help anything. Its worthless on the aluminum heads as far as flow goes.

[oxrabidus]

really? i figured that would always help... well would undercut 1.5 exhaust valves benefit the flow on the exhaust side?

[geoffinbc]

If you relocate the valve guides and modify the combustion chamber and rocker studs it might work. But there is no way in hell it will work the the valves in their current position.

[oxrabidus]

youre an iron head enthusiast eh? that is probably not worth the trouble... but maybe you could tell me how much of a gain it is to gasket match the ports?

[geoffinbc]

Well I cannot put a number on it. But when you see how bad the mis match is between the stock ports it is clear that a little work goes a long way to improving port flow.

[87S10]

You'd probably see the most gains by having a set of customs valves made with a 8mm stem,nail head design on the intakes with thick .120 valve margin and a tulip shape for the exhaust head,also with a .120 valve margin and stay with stock valve dimension would be my suggestions to help assist in maintaining higher port velocity due to the iron heads short port runners. I haven't had an opportunity to have one of these heads flowed yet,just going by what I've observed visually.

[geoffinbc]

With valve guide inserts you could use aluminum head valves. Although they have a dish in the face and would lower compression a bit. But you would get the 8mm stem

[oxrabidus]

i thought about that... the 3500 valves... plus theyre lighter arent they? any ideas as to how much this would gain on a stock 3.4l? maybe 15 - 20 hp?
im gonna have the ports gasket matched and am digging the 3500 valve idea...

[oxrabidus]

oh and im also getting flat top 0cc pistons instead of the stock dish type... so i imagine i could stand to lose a pinch of compression...

[geoffinbc]

15-20 is doubtful. 10 if your lucky.

[oxrabidus]

15-20 is doubtful. 10 if your lucky.

wow... almost makes it pointless to spend the money...
that is even with the 8mm stem?

[geoffinbc]

There is only a .028" difference in stem size. Its not going to net you a ton of power. But it is a low cost mod. If i had time to dick around when I built my engine I would have done it.

[oxrabidus]

but if i just get 10 hp frm gasket matching the ports the 8mm valves, plus the lighter weight of the valves... thats pretty bad...
but i have a question... since no one anywhere can answer this... how much higher if any will the compression be if i use flat top pis instead of factory dish pistons with 3500 head gaskets?

[BillS]

but i have a question... since no one anywhere can answer this... how much higher if any will the compression be if i use flat top pis instead of factory dish pistons with 3500 head gaskets?

You have already said you are using flat tops. Why would you say that if you don't even know what compression it would give you? You just like the name flat top, or......