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Installing pistons in engine block during rebuilding.

Fix A Connecting Rod Knock - GM 4.3 V6:

Engine Rebuild Part 7 - Installing The Pistons

May Also Apply To Chevy / GMC
350 Cubic Inch V8 Engines

In This Article:
The cylinder walls and piston rings are oiled. Pistons are placed inside a piston rign compressor and then tapped into the cylinders. The connecting rod caps are installed with Plastigauge to measure the bearing clearance.
Related Articles:
Skill Level:
4 (Advanced)
Time Taken:
About 4 Hours
Bruce W. Maki, Editor
Project Date:
August 2011
By Bruce W. Maki, Editor
By Staff
Start >>



Oiling The Cylinder Walls:

I wiped the cylinder wall with a clean paper towel and brake cleaner (to remove the oil I applied after cleaning the block, and all the dust that has accumulated since).

Then I used a small foam paint brush to apply motor oil to the cylinder wall.

Actually, the lubricant I used was about 2/3 motor oil (5W-30 for this GM engine) and 1/3 Lucas Oil Stabilizer.

Applying motor oil to cylinder walls before installing pistons.


Dipping piston in motor oil before installation.
Oiling The Piston:

I dipped the top of the piston in my oil/Lucas blend.

This is necessary so the piston will slide through the piston ring compressor and into the cylinder.



Then I placed the top of the piston in the piston ring compressor as shown. Note that the wide section of the dark blue steel band (red arrow) goes away from the piston.

The narrow part of the band goes against the engine block when the piston is installed. After tightening, the band has a slight taper, with the narrow diameter at the end with the narrow blue band.

I tightened the ratcheting key with the supplied L-shaped tool.

Piston placed in piston ring compressor.


Installing piston in engine block with ring compressor.

I inserted the connecting rod into the cylinder and held the piston ring compressor tightly against the engine block.

Note that the crankshaft was turned so the rod journal was at Bottom Dead Center, which means that the crank is as far away as possible from the piston.



Pushing The Piston Into The Cylinder:

I used the handle of a large hammer to tap the piston into the engine block.

Tapping piston into cylinder with wooden handle of hammer.


Using hammer handle to tap piston into cylinder.

Once the piston was fully inside the cylinder, I removed the piston ring compressor and continued tapping the piston into the block.



I guided the connecting rod (red arrow) until I could position it so the rubber boots were on opposite sides of the crank journal.

I tapped the piston until the connecting rod had fully seated itself onto the crankshaft journal.

Then I removed the plastic booty things.

Guiding connecting rod onto crankshaft journal during piston installation.


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Piece of Plastigauge placed on rod journal to measure bearing clearance.

I placed a small piece of Plastigage (arrow) on the rod journal.



I installed the rod cap and tightened it to the required torque.

For this engine (1999 GM 4.3 V6) the torque spec is 20 foot-pounds AND THEN and additional 70 degrees of tightening.

Tightening the connecting rod cap nuts after piston is installed.


Measuring width of  squashed Plastigauge to determine bearing clearance.

Then I removed the connecting rod cap and compared the squashed Plastigage to the scale on the package.

The scale indicates about .0015 inches of clearance between the bearing and journal (that's fifteen ten-thousandths of an inch). My Haynes book says that acceptable clearance is from .0013" to .0035", so I'm very close to the low (desirable) end of the range of acceptable oil clearance.

I cleaned off the Plastigage with a paper towel and brake cleaner.



I applied a dab of assembly lube to the rod cap.

Applying assembly lube to connecting rod cap bearing.


Applying assembly lube to rod journal on crankshaft while installing pistons.

And I also applied some assembly lube to the journal beneath the connecting rod. To get a little space underneath the crank journal, I rotated the crankshaft a few degrees to slide the piston down, then I turned the crank back so there was a gap between the connecting rod and the journal. Then I dripped some assembly lube into the gap. I also applied some lube to the bare part of the journal.

Then I installed the rod cap and tightened it to 20 foot-pounds. I'm not going to do the final torqueing until all the pistons are installed (and when I've bought a tool to measure degrees of rotation of my ratchet wrench).


After installing each piston, I rotated the crankshaft a few turns to spread the assembly lube around.


The bottom of the engine after all 6 pistons had been installed.

At this point the connecting rod nuts had only been tightened to 20 foot-pounds... I had not yet tightened them the additional 70 degrees that is required.

Bottom of GM 4.3 V6 engine after pistons have been installed with new crankshaft.


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Angle torque gauge, KD Tools.

This is an angle torque gauge.

This tool snaps onto the torque wrench, and then the socket snaps onto the torque gauge.

The L-shaped rod is supposed to be set up to touch some part of the engine and be held stationary while the torque wrench is turned. That is a tricky action to do, and having a helper to hold the pin might be a good idea.



With the piston at Bottom Dead Center, I used the torque wrench and angle torque gauge to tighten each rod nut the additional 70 degrees required.

Tightening rod cap nuts with an angle torque gauge.


Next Page: Part 8 - Installing The Timing Chain And Harmonic Balancer

Previous Page: Part 6 - Installing Piston Rings

More Info:
Tools Used:
  • Piston Ring Compressor
  • Angle Torque Gauge
  • Torque Wrench
  • Socket: 9/16"
  • Plastic Pail
  • Small Foam Brush
  • Small Hammer With Wood Handle
  • Protective Boots For Rod Studs
Materials Used:
  • Motor Oil
  • Plastigauge
  • Assembly Lube
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