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My experience is with B20s in 122s with carbs, mostly
but I would second what John said except I am not sure
that hardened seats are a necessity unless you are going
to do a lot of continuous high-speed driving (a few days a
week). You can avoid a LOT of valve grief by just keeping
your valve lash where it ought to be or a little looser. (0.020-
0.021"). Keeping your ignition timing right is also beneficial,
because late timing causes a lot of heat to get away out the
exhaust valve and is about like a torch on it.
You may find that your cam and/or lifters are going downhill.
B20 cams are famous for that. If so, get an IPD cam and
lifter kit, using the 7001 cam. Don't get the double valve
springs -- they do more harm to the cam than good for
performance as long as you are below about 6 - 6.5K RPM.
This cam lugs well and turns on pretty hard above about
2500 on up. The B20 version is a billet cam and very
reliable.
(I had a couple soft welds on a welded B30
version. Apparently the volume is not good enough to
justify a billet cam for the B30. IPD DID replace the bad
cam for me and would have paid me for installation also.
The replacement in my 164, now probably 7 or 8
years old, is still a pretty impressive performer.)
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