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Hello All,

Getting ready to reassemble a freshly machined 261. I was reading the Factory manual and it said to use .002 shims on the main bearings to start with in order to make sure the crankshaft is properly aligned. The new bearings that I have don't have anything that look like a shim, what are they made out of and is it something that I will find at my local parts store? Is it even worth avoiding placing these shims or is it a must? Thanks, any advice on this and points beyond are always appreciated.

Shane,
I'm not familiar with a 261 as per say, but I'll see if I can shed some light on the situation. The older model engines had poured babbet rods and mains. Somewhere around '53 or '54 they GM changed to replaceable inserts. If you have inserts, they (along with the crankshaft) should be machined within tolerance and shims won't be needed. You could get some plasti-gauge and check the clearance (should be about .0015 to .003--check your manual) It's been 30 years since I have rebuilt that type of engine. Maybe someone else can shed more candlepower to this.
Truck Tinker

If your manual is for a 1953, I don't think that it is giving you the correct instructions for a 261, maybe a 216 or older style 235. I don't think that the 261 would use shims in the main bearings.

Truckernix & Tinker(er),

Thanks for the reply...that would answer my suspicions. You guys are very perceptive, I am as a matter of fact using the '53 manual. I didn't even stop to consider which engine they were basing this advice on. Thanks, I will go ahead with the installation of the bearings. One other thing it mentioned was gapping the cam thrust plate with the proper amount of gaskets to assure a 'given' clearance. I can't remember the clearance, want to say .003-.005 Anyhow, I suppose I will need to pull the cam back out to do this since my machine shop put it in. Should the cam journals be PERFECTLY in line with the bearings or is it possible that they might overlap the edge one way or the other?

Can't say for sure right off the bat, but I would think that a small degree off wouldn't hurt, but check any specs you can because now is the best time to make sure everything is right.
Truck Tinker

I can't help you on the cam thrust clearance issue but the relationship between the cam journals and the bearings, in the position along the length would not be particularly precise. The spec may be associated with hom much clearance there is between the timing gear and the front plate.