Rebuilding a chev 3.1 engine

they are a standard size for each make of piston and to get a measurement for the bearing and pin you will need a workshop manual that has the engine specifications page
if you know an engine rebuilding shop , they will have the sizes available as they check bushes and pins before assembly

the rings are staggered. (they spin, as the engine runs)
staggering them 120 degrees, gets them started in good way.

rod bearings. they only go one way, they have index tangs.
you sound like this is your first build. did you read at least 1engine builders book first? or read the FSM on the ALto?
it covers this. 100% the assembly.
we cant help you.
we dont know where you started, or what you are doing
nor what step in the 100s of steps, you did or skipped.
did you mike every thing, in step 1?

For the 12 Pointed Head Bearing Cap Sub-Assembly Bolts
Start from center bolts and tighten in a clockwise rotation working out
Step 1 all bolts 22 Nm or 16 ft lb
Step 2 all bolts 44 Nm or 32 ft lb
Step 3 all bolts 45 degrees additional clockwise rotation using an angle indicator.
Step 4 all bolts 45 degrees additional clockwise rotation using an angle indicator.

Hexagon Head Bearing Cap Sub-Assembly Bolts
1ZZ-FE Engine 18.5 Nm (14 ft.lb)
2ZZ-GE Engine 18 Nm (13 ft.lb)

Connecting rod:
1. Apply a light coat of engine oil on the threads and under the heads of theconnecting rod cap bolts.
2. Install and alternately tighten the 2 connecting rod cap bolts in several passes. Torque: 1ZZ-FE: 20 Nm (204 kgf-cm, 15 ft. lbs.) 2ZZ-GE: 30 Nm (306 kgf-cm, 22 ft. lbs.) If any of the connecting rod cap bolts does not meet the torque specification, replace the connecting rod cap bolts.
3. Retighten the cap bolts by 90 more
4. Check that the crankshaft turns smoothly.

TORQUE SPEC FOR ROD BEARING BOLTS 19 - 24 FT LBS TORQUE SPEC FOR MAIN BEARING BOLTS 60 - 70 FT LBS, CRANKSHAFT PULLEY BOLT 85 - 100 FT LBS. MAIN BEARING OIL CLEARANCE .0005 - .0022 CONNECTING ROD OIL CLEARANCE .0008 - .0015 / SHAFT END PLAY .004 - .008 / AND ROD SIDE CLEARANCE IS .004 - .011 HOPE THIS HELP THIS INFORMATION I GAVE YOU IS INLINE 6 -200 AND INLINE 6 - 250 ENGINES

I show the main bearing torque to be 70 ft.lbs.
The rod caps are torqued to 38 ft.lbs.
Best of Luck to you..

a thumping sound could be a rod knocking when the moter is under a load it caused by worn out rod bearings or main brearings. doing such a repair often reguires removing the engine and rebuilding the moter.

If the oil pump does not work, the entire engine will lock up and be totally useless. You will need to do a complete rebuild of the engine, including main bearings and rod bearings. Sometimes it is easier to buy a rebuilt engine, in the area of $1800.00. Rebuilding will cost 800.00 plus 15 hours lablr.

Crank Main caps Tightening Torque

For the 12 Pointed Head Bearing Cap Sub-Assembly Bolts
Start from center bolts and tighten in a clockwise rotation working out
Step 1 all bolts 22 Nm or 16 ft lb
Step 2 all bolts 44 Nm or 32 ft lb
Step 3 all bolts 45 degrees additional clockwise rotation using an angle indicator.
Step 4 all bolts 45 degrees additional clockwise rotation using an angle indicator.

Hexagon Head Bearing Cap Sub-Assembly Bolts
1ZZ-FE Engine 18.5 Nm (14 ft.lb)
2ZZ-GE Engine 18 Nm (13 ft.lb)

Connecting rod:
1. Apply a light coat of engine oil on the threads and under the heads of the connecting rod cap bolts.
2. Install and alternately tighten the 2 connecting rod cap bolts in several passes. Torque: 1ZZ-FE: 20 Nm (204 kgf-cm, 15 ft. lbs.) 2ZZ-GE: 30 Nm (306 kgf-cm, 22 ft. lbs.) If any of the connecting rod cap bolts does not meet the torque specification, replace the connecting rod cap bolts.
3. Retighten the cap bolts by 90° more
4. Check that the crankshaft turns smoothly.

Mains, 80, rods, 33...Don't forget to plasti-gauge bearings before final install. Make sure there isn't any lube on saddles or bearing backs before putting it together. Use pre-assembly lube on bearing faces and crank pins. Check that crank spins freely after each cap is torqued. If not find out why before continuing.

MAKE SURE THE CRANKSHAFT IS NO DAMAGED.IF IT IS THE NEW BEARINGS WILL GO BAD QUICKLY