This week in our Mailbag, the Summit Racing tech department is troubleshooting bearing-clearance measurement and engine-cranking issues in a small block Chevy.


Q: I’m building a 350 Chevy engine and have a problem. When I torque the main bearings down, the crank is very hard to turn over. When I install the connecting rods, the starter won’t turn the engine over. But when I loosen up the main caps, the engine turns over easily. I have miked the crank and it’s right on. What is causing this problem?

307 bare block bottom end prior to crank installation
(Image/Jim Smart)

A: You said that you miked the crank, but did you plastigage it and the connecting rods with the bearings installed and torqued down in the block? This would have given you the bearing clearances for the crank’s rod and main journals. You might find your clearances are way too tight, making it hard to spin the engine.

You might also want to check the following items:

  • Crank alignment
  • Shape of rod big ends (rods may need resized)