5.3 swap starter clunking noise when cranking...

[bs46488]

Needs some advice on a LS swap (not on a C10, put in a Big Block). This swap is in a 1970 Nova.

So Sunday was the official day to start the car. Everything is done, no leaks, fuel pump relay seems to be working correctly, I even ran exhaust on the car.

Decided to crank the engine over (pulled the fuel pump relay for a no start situation) to see what the mechanical oil pressure gauge would do and ran into 2 problems:

1) There is a nasty clunking noise when the starter cranks. Inside the car it feels bad, it sounds like a loud clunk almost like the driveshaft is hitting the floor pan (its not moving, I checked). Outside the car, it does not sound as bad. It just sounds like the starter is not meshing correctly or engaging enough, or maybe just hitting he flywheel.

2) I didn't crank a lot because of issue #1, but I didn't see any movement on the oil pressure gauge

Looking for suggestions on issue #1.

A little of the background: 2002 Silverado 5.3 with 4l60E (supposed to have 87k on it). Got the engine, trans, wire harness and ecu as a pull out. Didn't separate the engine and trans. I only removed the starter to put in the new Holley oil pan, then bolted it back in place. Used the LT1swap.com for harness modification and he flashed my ecu.

I'm running a battery in the back with 1/0 welding wire, using a ford starter solenoid in the trunk and have a little jumper wire from the battery lead to the "S" start wire on the starter. Brand new battery. Battery is grounded in the trunk to the body. Engine has 3 grounds up front from the block to the body and chassis.