Hot Rod Blog Engine Assembly Blog, Day 4
Check main bearing bore alignment
Lay a straight edge across the saddles and make sure there isn't more than 0.001" clearance with a feeler gauge. I could detect absolutely no clearance on my block. If you get too much clearance, you're going to need to have the block align bored.
Check thrust face distance
You can do this with a snap gauge, but I took a different tack. Drop a bearing into the thrust face and then use a feeler to measure the additional clearance. Add the two numbers. You should get 1.125" plus or minus 0.001" on a Cleveland or Windsor/SVO block. Mine came out between 1.124 (loose feeler) and 1.125 (wouldn't fit) so I'm good.
Thrust face distance measurement. First check with a feeler gauge.
Big box o' eBay Chinese Mikes. Very nice!
Then check the bearing width with a micrometer. Add the two together for thrust face distance.
That's the thrust face. The two flat faces locate the crank from sliding along it's axis.
Knife edged counterweights. This Sonny Bryant crank is a beautiful thing!
Check connecting rod and main journal out of round
Measuring journal out of round is done using a micrometer and taking several readings of journal diameter. These readings should not differ by more than 0.0004" out of round for a racing engine that's fully blueprinted. If you're not so particular, Monroe's book, "Engine Builder's Handbook" claims you can live with as much as 0.0015".
In practice I found it extremely hard to get all the measurements to be repeatable enough for me to verify within 0.0004" of accuracy, but my crank was good. If even journal is off by too much you'll have to have all the journals reground.
My crank has 2" con rod journals and 2.75" main journals. This is not stock, but I got the con rods with the crank so I'll be good to go.
Check crank journal taper
Checking taper is done similarly to checking out of round except you're taking multiple measurements by moving left to right across the journal face rather than around the circumference. The standard for taper is even more demanding: 0.0003"!
Chamfer crank oil holes. Install restrictor kit
Done and done before I ever got the crank and block. You can see some of the chamfering on the crank above. These steps ensure the oil goes where we want it too (restrictors) and improves the dispersion of the oil over as much bearing surface as possible (chamfering). This all goes to increase the longevity of the engine.
Check Crankshaft Runout
Runout is a measure of how straight your crank is. You measure it with a dial gauge on a magnetic base. Drop the front and rear main bearing halves into the block. Put a couple drops of oil on the bearings and then lay the crank in them. Attach the dial indicator to the block with it's magnetic base and place the tip on the middle main journal. Rotate the crank and measure how much the dial indicator moves. Mine was 0.00125". Allowable maximum is 0.002".
All material © 2001-2006, Robert W. Warfield.