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Discussion Starter #1
I've been wondering about this for awhile out of curiosity. But what would be the negative effects of putting 1.94 valve seats in a head. Assuming the throat directly behind the valve would be larger. Then running a 1.90 valve lapped and ground to the appropriate angles to match the seat?

Would the contact patch of the valve be to small causing the valve to stick, distort or maybe crack... maybe beat the valve seats to death? Who knows but I've wondered about that for years but never had anybody to ask :ROFLMAO:
 

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I'm no techie from any standpoint, but just from the description you posted I can only guess what would happen. At .004 difference the valve lapped in would seat a very small amount higher?(maybe .001?) which might change the valve spring installed height by another .001? Kind of a curiosity though, maybe the smaller diameter would have an effect on flow? As far as seat contact, I don't think there would a problem as long as there was enough contact to achieve a good seal. Of course, being an novice at these things I could be inviting an engine explosion! What exactly are you thinking it would do?

Joe
 

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X2

larger seats are done all the time,
with a larger throat [bowl job] ..
but now days you can get super large heads..
like 240cc ports with 2.100 valves.. [depending on the bore]
[/QUOTE]
In my defense it was after midnight but I did displace that decimal point!
X2 with the off the shelf super large heads.

Joe
 

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Discussion Starter #5
87ls Yeah that would be 0.04 difference or 0.02 all the way around if you measure from the center.

JJLT I agree there are great off the shelf heads for the larger bore engines. I have afr210's planned for my 434 when I get all the parts collected. In the meantime I have a free 305 with 081 heads sitting in a parts car. I'm tempted to slap a cheap rebuild kit in it with a little head work so I can complete the frame off and have it looking good and drivable. Rather than building the 434 now just to sit in the shop with the car out of commission in pieces and I refuse to put that painfully slow 100hp v6 with a water drinking problem back in it:ROFLMAO::ROFLMAO:
 

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x2 more coffee Joe..
AFRs are nice heads..

im sure someone has tried it..
not a lot of wiggle room on a valve seat face tho..
i'v found, even if you DIY, it still cost more..
just sayin there is a lot of things worth 1hp,
it just takes 10-20 of them to be able to feel it..
like doing a 5angle valve job,
or small stem valves, if you need guides?? under-cut valves..
more valve lift, more duration on the cam..
but trying to up-grade old scool heads to match
even "as cast" or CNC heads now days, your time is worth something
and its taking up seat time in the old Hotrod..
.
if your maxed out on everything else and still need 1hp??
I don't know what it would do, better or hurt..
heres a 2013 article with
valve curtain calculation, try it.. I haven't had enuff coffee yet ether..
valve curtain area
.
it says
To calculate valve curtain area you can’t go by the valve diameter itself. You have to use the flow diameter,
which is where the actual valve seat begins and that is generally about .040-inch smaller than the measured valve diameter.
 
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