The only active gate is gate 3 at the back of the engine. You have to trigger ball lock ("Lite Kickback" under the dragstrip) in which case gate 3 closes and the ball is stuck in the engine. Gates 1 and 2 are both passive. When the ball is stuck in the engine and rev mode starts, the ball shakes back and forth. At the end of revving, if gate 2 is adjusted correctly, the ball should move back under the gate 2 flap and fall into locked position. Sometimes this may take several tries by the engine. After three balls are locked, they will be ejected one at a time for kick-back play.

If a weak shot happens to get past gate 1 but not gate 2 then it will fall into the locked position. If you are not in lock mode (the 3rd light to the LT-5 ramp "LT-5 LOCK" is not lit then the ball will be kicked out of the locked position. The only time the ball will stay in locked position is when the "LT-5 LOCK" light to the ramp is turned on. This could also happen with a weak shot that gets pass gate 2 but not gate 3.

When the "LT-5 LOCK" light is not on, gate 3 is open and the ball will normally pass through the engine in a loop.

Check out this link:

https://pinside.com/pinball/forum/topic/corvette-repro-engine-wires

The second gate needs to be adjusted. It is a little tricky. It should never stay open. The gate needs to be tweaked by bending the gate wires that hold up the flap. After revving, the engine should slowly move to center position. At which time the ball should move under the gate 2 flap and slide into the the lock position. Gate 1 prevents the ball from sliding back down the ramp.

The "LT-5 LOCK" light needs to be on for the ball to be actually locked. This is triggered by hitting the switch near the dragstrip labelled "LITE KICKBACK".

Interesting.....

I do have an early production machine (Delco logos on the back glass vette bumper, no centering adjustment pot on the engine).
I tried the solenoid tests. Nothing happens with test #2, test #5 activates the rear gate.

I have removed the gate #2 by removing just the 2 screws. Nothing is attached to it such as a linkage to a solenoid. This is how I tweaked it to get the ball to drop in the locked position. Hmmmm!

I can see having gate #2 attached to a solenoid would be a big improvement.

Here is a picture of mine:
(I did add a strip of stainless steel between the right side of gates 1 & 2 because there was a crack in the plastic ramp)

Gates 1 & 2.jpg

EUREKA!

I have to apologize to everyone. I have found the gate 2 solenoid and spring. The spring was not connected to the gate when I bought the machine. I inadvertently covered the slot with the SS support that I made.
I was looking for the solenoid to be under the play field. It is hidden above the pf and under the ramp. I notched the SS support and connected the spring. Hey.... It plays a whole lot differently now. Thanks, this is a great site!

ActiveGate2.jpg