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.)