Bigger valves for iron heads?

[Doubt_Incarnate]

I know about L.O. heads with small valves, and the H.O. heads having 1.72"/1.42" valves as far as the iron heads go. and all the aluminum heads having the larger size up to the gen3's getting even bigger intakes 1.76".

My question is would it be possible to swap gen 3 valves and their guides and seats into the older iron heads. I know the iron heads use valves with thicker stems, i'm not sure in the lengths of the atual valves themselves. I figured if you could move the seats, stems, over you could physicaly get the valves to fit and seal properly. But the bigger matter is are the longer or shorter than the 11/32" stems.

I can see how having a larger valve (with apropriate head porting to match the seat) would slightly benifit performance. and since the stems are thinner, more airflow, and lighter. providing they are long enough or not too long.

[rx191]

there are stainless vales that will fit the iron head motors for inatke and exausht, the inatkes are even undercut for even more flow. a 1.76 will fit the chamber fine i think you mite even be able to fit a 1.78 in there

[Doubt_Incarnate]

yeah, i thought about putting bigger valves in, like from the 3.8. but then the aluminum heads valves are thinner 8mm vs 11/32" (8.4xmm) and probly a little lighter, that and i'd only need to replace half the seats. i hardly see over 5000rpm so i dont need heavy duty stuff, i am thinking about boost tho so i might have to keep that in mind. i dont hear anyone complaining abut their valves, just trannies.

[SappySE107]

Who makes the undercut valves for the iron heads besides SI? SI valves hurt flow, even their port flow series flow worse than stockers without modifying them. Since the valves aren't canted, you wont get more unshrouding around the valve as lift is increased which might offset the flow capacity for larger valves.

[rx191]

look up valves for fords some of them use the same size haed and stem diamter as iron head motors, the only difference is the stem is about 0.080 longer witch will not affect anything if you adjustable valves, and you are right if you go to big on the size they will flow worse because they will be shouded by the chamber but you should be able to go to a 1.76 with any problems over that and you mite need to modify the chamber to help flow

[Doubt_Incarnate]

I'm trying to stick with the stock gm parts, i just want to see if its possiblt to swap the 3400 valves and hardware to the iron heads. points being thinner stems let more air flow, and are lighter. and the .04" of head diameter probly wount hurt. just checkin to see if anyone has looked at it before, if there's anything i should look for... etc. the obvious thing is the valve guides since the stems are smaller. and i'd probly need the 3400 stem seals and intake seats.

[sharkey]

when i had my guides done, i was told that it is possible to use 3.8l buick valves. im not sure whats all involved.