This writeup comes from Hudini (not to be confused with Whodeanie) of the Pennocks Fiero Forum. It's reprinted with his permission. The reason for using the SBC cam bearings is that they have a larger bearing surface than the stock 3.4 cam bearings.
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Today I replaced the cam bearings in my 3.4L OHV engine. I learned a few things I'd like to pass along. Plus I'd like any feedback on what I did (i.e I did it all wrong and need to do it again...). I used the Proform Cam Bearing removal tool for small block chevys as sold by Jegs, Summit, etc for $70 plus shipping. I also used SBC cam bearings for a 1995 5.7L V8 as recommended by the 60* V6 power manual. They are wider than stock V6 bearings. The brand was Sealed Power Series A and the type was bi-metal. Cost is about $20.
First thing I learned: Remove the 3.4L cam sensor BEFORE removing the #1 cam bearing. It will be in the way.
Second: #1, 2, and 4 cam bearings have to be knocked inward then pulled back through the journal opening. #3 can be knocked outward and pulled through the #4 journal. Not hard to do as the cam bearings are aluminum and pull back out with a little help from a hooked tool or screw driver. Careful you do not scratch the journal with your tool. The bearing will not scratch it.
Third: The #1 cam bearing on the 3.4L engine is 2.010", but is 2.020" on the SBC. What this means is you have to use the #2 SBC cam bearing as the #1 bearing in the 3.4L engine. So SBC #2,3,4,5 = 3.4L #1,2,3,4 bearings. (#1=2.010, #2=2.000, #3=2.000, #4=2.010)
Fourth: Since the #1 bearing has 2 oil holes and you are using a bearing which only has one hole, you need to drill a 2nd hole to match the old #1 bearing. Deburr the new hole and chamfer as best you can.
Fifth: I placed the oil hole at the 4:30 position as recommended by the 60* V6 power manual. On the #1 bearing the 2nd hole ended up facing the oil feed hole drilled into the block. This hole is where the oil comes from the pump.
Last, the old #1 bearing has a .25mm deep groove by the lower oil hole on the outside of the bearing. It is supposed to let oil out on the backside of the timing chain and sprocket. The new bearings do not have this groove (neither the #1 or #2 I used in the #1 position).
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