NS300L Head Bolt Thread Repair 2015 Silverado L86

[TigerTruck]

Basically, I Some background: I have another active thread called DOD Delete and New Jersey OBD2 inspections. have had AFM lifter failure on cylinder number four 4 times now. Dealer covered the first three times. Now warranty is expired. The subject of this thread is the problems I ran into replacing the lifters and VLOM. During assembly, the seventh head bolt tightening the final 60 degrees resulted in the threads pulling out. I guess 4 times removing and replacing the head was the limit. Research on fixing the threads lead me to the NS300L M12x1.75 Head bolt repair kit for the Gen V engines, sold on eBay. The kit is rather pricy but it includes just about everything needed to repair all 20 head bolts. The kit is very straight forward to do but doing the job with the engine in the vehicle presents some obstacles that needed to be conquered to complete the job. Since the issue was on the Right Passenger side, that is the only side I worked on, doing all 10 bolt holes. The kit included enough inserts to do all twenty head bolt holes.  I would say that if you are skilled enough to disassemble the right side of your engine, then this job is not that difficult. Clean all oil and antifreeze from the head surfaces and use wide painters tape to cover the left head intake openings on the head and cover the whole right side block face to prevent chips from entering the engine.

 

The first thing to do is remove the passenger side wheel liner. That provides lots of space to access the exhaust manifold, spark plugs, wires, and lower head bolts. Also, removing the exhaust manifold is a must. Another thing to do is take off at least the tire on the side you are working on and lower the truck as much as possible. Even doing this, I needed a step ladder and a seat cushion to lean into the engine compartment to reach anything at the rear of the block. I would say that 7 of the 10 head bolt holes are readily accessible with the long drill bit that comes with the kit. The rest you need to get creative. It became obvious that a ½” drive angle drill is out of the question. Just not enough room. I scoured Amazon to find 17/32” drill bits with a 3/8” shank. Plus, you will need a 3/8” drive angle drill adapter. I found the perfect one on Amazon but it was so cheap that I was barely able to use it on the three holes before it stripped the gears. I found two drill bits that will work but they need to be modified slightly as per the vendor. I used a hand diamond file from Home Depot for $8 to file the flutes and ground the tip on a bench grinder. I cut about 1” from the longer 3/8 bit shank for more room.

[TigerTruck]

 

 

This is the short drill bit I found on Amazon: 

 

NordWolf 17/32" M35 Cobalt Stubby Drill Bit for Stainless Steel, Hard Metals & Cast Iron, with 5/16" Hex Shank for Quick Chucks & Impact Drivers

 

[TigerTruck]

 

Per the Vendor, This must be filed on all drill bits used.

[TigerTruck]

 

 

 

Vendor says this must be ground down to prevent drilling past the bottom of the hole

[TigerTruck]

This is the intermediate drill bit. The shank needs to be cut so the drill fits right up to the reduced part of the bit.

 

Drill America - DWDRSD3/8X17/32 17/32" High Speed Steel Reduced Shank Drill Bit with 3/8" Shank, DWDRSD Series

[TigerTruck]

 

This is all the drill bits I used

[TigerTruck]

 

Tape the block. Tape does not stick to good if there is even a small amount of oil on the block

[TigerTruck]

 

This is the angle adapter I used. Very cheaply made but it barely did the job before breaking.

 

90 Degree Right Angle Adapter, 0.8-10mm Right Angle Bend Extension 8mm Hex Shank Cordless Drill Attachment Adapter for Electric Drills(black)

[TigerTruck]

The holes in question are the two next to the firewall and the next lower one from there. I must have not taken a picture of the angle adapter being used. Basically, I set up the jig and used the short drill bit. Things may get tight so you may need to put the bit in the jig and attach the angle drill adapter to the bit. Then attach your drill to the adapter. Drill as far as you can. Back out and remove the adapter then remove the bit. Remove the jig and repeat with the short drill, being careful not to tilt the drill bit. Use air to blow out the chips. Be careful, the chips will fly everywhere. Wear eye protection. After drilling with the short bit, repeat the process with the next 3/8 shank bit without the jig. This bit will go to the bottom of the hole. Remove the adapter, then remove the bit. Use air to clear the hole. Wear eye protection. I used a Depstech endoscope for every hole. You need to make sure the hole is drilled to the bottom, then to make sure the hole is tapped to the bottom. Instructions say to not use any powered drills to tap the holes. I used a 7/16” ½” drive 12 point socket to do the tapping and a 3/8” drive speed wrench to remove and screw in the taps. Tap Magic was added each time to the drill and tap. The small tap can be screwed in as much as you can. Remove the tap, remove the jig, and clean the hole. Insert the longer tap and screw down with the speed wrench, then tap ¾ of the way down with the rachet. Remove tap, blow out hole, and screw the tap 7/8 down, repeat and finally screw the tap down until it stops. Do not force any futher. Remove, blow out, inspect with endoscope.

Edited February 15 by TigerTruck

[TigerTruck]

 

Short bit

[TigerTruck]

 

Medium Bit

[TigerTruck]

 

Long bit that comes with the kit

[TigerTruck]

 

Stock undrilled head bolt hole

[TigerTruck]

 

Fully drilled hole. That mark in the center is where the ground tip of the drill bit hits.

[TigerTruck]

 

Newly threaded hole. Appears to be off a little bit. This only happened withe one hole.