HEAD BOLT THREAD REPAIR SYSTEM

I found that the Northstar engine is notorious for the head bolt holes stripping, and a larger diameter GM-approved "second repair" insert was available, but it also had the same fine threads as the failed GM-approved "first repair " inserts. The last thing that I wanted to do was to install another fine thread insert, because if they failed, I would have had no other opt ion than to replace the engine block. I am a Tool and Die Maker by trade, and I developed the NS300L " Insert System out of necessity and frustration.<br><br> The NS300L " Insert System is a thread repair kit designed to outperform all other kits on the market designed for the Northstar engine. Unlike thi n inserts with synchronized internal and external fine threads, the NS300L " Insert is a far stronger insert because of its longer length, bigger diameter, and coarser external thread. This prevents the insert from expanding under high torque, and allows the load to be distributed to a much larger area.<br><br> As a result, the load per thread is much less, significantly reducing the chances of cracking the block. The NS300L " Insert System has over three times the thread engagement within the aluminum block than the GM-approved first repair insert, over two times that of th e GM- approved second repair insert, and almost four times that of the common coil type inserts. There is nothing wrong with those ot her type inserts, they very well designed inserts for most applications.<br><br> The challenge with them is they do not always get past the deteriorated aluminum and into virgin aluminum due to their smaller diameter and fine external threads (the same fine threads as the head bolt that faile d in the first place), and have a tendency to pull out during the head bolt tightening process. Occasionally, those other types of inserts have failed only a few hundred miles after the repair. I have had several people contact me with this challenge, including several Cadillac technician s.<br><br> They found the NS300L " insert gives them a much stronger, more reliable repair, and in return, saves them the expense and frustration of failed repai rs. One dealership informed me that they had stopped repairing Northstars with stripped head bolts on engines having over 100K miles, d ue to the high number of failed repairs with the GM-approved inserts. They felt the NS300L " Insert System would be the answer to this challenge, and they have been very pleased with the results.<br><br> We receive positive feed back on a regular basis from Cadillac and other technicians, about how impressed they are with the quality, strength and the ease of installation of the NS300L " Inserts System. In fact, the NS300L " Insert System is now the thread repair system of choice for many Cadillac tech's, general automotive tech's, automotive machine shops, and hot rodders. More facts and advantages of the NS300L " Insert System The NS300L " insert also allows you the option of using the properly engineered factory head bolts, or if you prefer, ARP ® brand head studs.<br><br> Both head bolts and studs are well engineered with rolled threads to prevent fatigue failure (rolled threads are at leas t 15-20% stronger than cut threads). They are also engineered with the correct physical properties to allow them to stretch and contract as the engine heats and cools (similar to that of a very heavy spring), helping to keep a constant amount of pressure on the head gasket during this he at cycle. This is vital for a long term repair and one of the reasons why the threads in the block start between 1 ¼ -2" (depending on the year), below the deck surface.<br><br> It not only allows for the properly engineered length of the head bolt or stud so that it has enough length to stretch and contract as it was intended, it also helps to minimize clamping load variations and engine block distortion....a common problem with aluminum engines. This is especially critical with engines like the Northstar that are made of aluminum, because aluminum has a very high expansion an d contraction rate. Much higher than that of steel.<br><br> For these reasons, be very cautious of custom repairs that have copied the 5/8-11UNC thre ad of the NS300L " insert. Such custom repairs often do not have the correct physical properties of OEM head bolts or ARP ® brand studs. A Custom head bolt or stud without the correct physical propertied and/or shorter than its original designed length, can result in a mor e rigid, less durable repair that could lead to fatigue failure after several heat cycles.<br><br> Rigid is the enemy of a long term successful repair, espec ially when fastening an aluminum head to an aluminum block that will go through many heat cycles. ARP ® brand head studs will work very well with the NS300L " insert, infact, I am very confident that you will not find a better combination on the market for high performance engines. Studs are typically prefered in race engines where the engine is consta ntly being torn down and rebuilt, and provide a more consistant torque load, but not necessary for your typical factory performance Northstar -2- Frequently Asked Questions Q- What makes the NS300L " Insert System more reliable than the GM-approved insert?<br><br> A- The NS300L " is a high quality high-strength insert, with a much courser external thread, having over three times more thread engagement within the aluminum block than the GM-approved "first repair" insert and over two times that of the GM- approved "second repair" insert. Q -Why should I purchase the NS300L " Insert System over other repair kits on the market? A -Piece of mind!<br><br> No other method has been proven to be a better, more reliable repair. Many customers, including several Cadillac Technicians, have commented that they were very impressed with the quality and strength of the NS300L " inserts, and wished they had purchased the NS300L " Insert system in the first place rather than going through the expense and frustration of a failed repair. Q -I noticed that the GM-approved kit has a stop-collar on the drill bit.<br><br> What keeps your drill bit from drilling too deep? A -The reason the GM-approved kit uses a stop-collar and locating fixture, is because the depth of their hole revolves around their locking feature. They have a slight flange around the top of their insert to create a positive stop so that the installa tion tool (a tool much like a thread forming tap) also forms the last couple of threads on the bottom of the insert.<br><br> The flange prevents the insert from turning during this process. This locking feature expands the last couple external threads of the insert, preventing the insert from turning out in the event that the head bolts would need to be removed later. This locking feature also creates a high amount of unnecessary outward pressure in an area of the engine block that is not overly thick to begin with.<br><br> The NS300L " inserts are designed without the need for a flange, eliminating the need for a stop collar and eliminating unnecessary outward pressure. The drill bit in the NS300L " kit is designed to stop when it reaches the bottom of the hole. This is accomplished by removing a portion of the drill point, preventing the drill bit from cutting deeper than the original hole.<br><br> The drill bit 9s cutting edges are also ground in a manner that helps prevent them from grabbing and twisting itself into the hole. Q -Can the NS300L " Insert System be used if the engine has previously been repaired with coil type inserts or GM-approved "first repair" inserts? A -Absolutely, and the NS300L " inserts may be your only recourse, short of buying another engine block.<br><br> Q -Can I re-use the original head bolts? A - To insure an even torque when re-assembling the head, GM recommends new head bolts. Head bolts, over time, are put though many heat cycles, that could effect their elasticity, especially if the engine has been overheated.<br><br> Q - Can ARP ® (www.arp-bolts.com), brand high performance head studs be used with the NS300L " insert? A - Absolutely. ARP ® brand head studs are excellent, well engineered, high performance, high precision studs with rolled threads, that will work very well with the NS300L " insert, in fact, I believe you will find no better combination on the market for high compression, high performance Northstar engines.<br><br> Studs are typically preferred in race engines with extreme high compression, and where the engine is constantly being torn down and rebuilt. They also provide a more consistent torque load. Q -In the future, will I be able to order the inserts alone, or do I have to purchase the complete kit every time?<br><br> A - The inserts can be purchased separate from the kit. Q - When is it recommended to use the optional Drill & Tap Alignment Jig? A - If the block has been repaired in the past with the GM "first repair" kit, the optional drill & tap jig will not be necessa ry since the unthreaded portion of the hole above the threads will be the same diameter as the drill bit provided in the kit.<br><br> Thi s works well as a drill guide, to keep the drill perpendicular to the deck surface when drilling out the remainder of the hole. If the engine has never been repaired before, it is highly recommended that you purchase the optional drill & tap alignment jig . If you have the GM-"first repair" kit available, the drill jig and bushing in that kit will work well to keep the NS300L " drill bit perpendicular to the deck surface since the drill bushing is the same diameter as the drill bit.<br><br> The tap alignment block in the NS300L " basic kit (also known as a tap block), is used to keep the tap square to the deck surface ... a common machine shop practice for starting taps square. If you are using the optional drill & tap align ment jig, you will not need the tap alignment block from the basic kit.<br><br> -3- -4- NS300L " INSERT SYSTEM M11x1.5 head bolt thread repair for 93-2005 Cadillac Northstar 4.6/4.0L V8 & 95-99 Oldsmobile Aurora 4.0L V8 BASIC KIT INCLUDES: 21 NS300L " inserts 1 Tap alignment block 1 17/32 d drill bit 1 5/8-11 three flute plug tap 1 5/8-11 four flute bottom hand tap 1 TAP ® MAGIC tapping fluid 1 LOCTITE ® 266 or Permatex ® high temperature, high strength threadlock (10ml.) 1 6" Steel rule 1 Insert installation tool OPTIONAL DRILL & TAP ALIGNMENT JIG INCLUDES: 1 Drill & tap alignment block 1 Head bolt spacer 1 Alignment pin 1 Drill guide bushing 1 Tap guide bushing WARNING Safety glasses must be worn when drilling, tapping, or blowing chips from the holes. Cutting tools are made of hardened tool steel and may shatter. If removing chips with an air hose, wrap a rag around the air nozzle to help prevent chips from blowing back into your face.<br><br> BEFORE STARTING, PLEASE READ THE INSTALLATION INSTRUCTIONS IN THEIR ENTIRETY . * Please read before repairing the 2004-2005 Northstar: Although the M11x1.5 is the preferred thread for torquing, in 2004 the Northstar went to a M11x2.0 head bolt thread in an attempt to fix the issue of the threads stripping from the block. The NS300L " Insert System will work very well in the 2004-2005 4.6L engine, but must be used in conjunction with the head bolts made for a 2000 Northstar.<br><br> The head bolts for the 2000 Northstar are the same length and diameter as the 2004-2005 head bolts, the difference is the 2000 Northstar has the M11x1.5 thread...the same as the NS300L " insert. For this reason, the head bolts must be torqued to the latest specs required for the 2000 Northstar. Test results: When installed correctly, the NS300L " Insert System has been proven to outperform the head bolt itself.<br><br> In every test performed, the head bolt was intentionally torqued beyond its yield point until the head bolt finally sheared. When the sheared part of the head bolt was removed from the insert, the insert had not pulled at all from its original set depth. These results have also been confirmed by those who informed us that they accidentally over-torqued their head bolts beyond their yield point.<br><br> They found that not only did the insert hold up to such high torque, the insert did not pull at all! -5- INSTALLATION INSTRUCTIONS Basic kit ( kit without drill & tap alignment jig) 1.Remove cylinder head alignment bushings from block (2 for each head). 2.Remove any old inserts that may have been previously installed.<br><br> You may have to check with the manufacturer or supplier about removal instructions. DO NOT REMOVE OLD INSERTS WITH THE DRILL PROVIDED -- THE INSERTS WILL DAMAGE THE DRILL BIT. 3.<br><br> Figures 1 -- The first thread of the head bolt hole starts about 1¼"(32mm) or deeper below the deck surface depending on the year of the engine. If the block has been repaired in the past with the GM first repair kit, the unthreaded portion of the hole above the threads will be the same diameter as the drill bit provided in the kit. This works well as a drill guide to keep the drill bit perpendicular to the deck surface when drilling out the remainder of the hole.<br><br> If the block has never been repaired before, it is highly recommended that you purchase the optional drill & tap alignment jig (see page 8). If you have the GM first repair kit available, the drill jig and bushing that comes with the GM kit will work well to keep the NS300L " drill bit perpendicular since the drill bushing is the same size as the drill bit . Using a 1/2" drill motor and the 17/32" drill bit that comes in the kit, drill the holes to depth (the same depth as the original holes).<br><br> The drill bits cutting edges are intentionally ground to a neutral rake to help prevent it from grabbing when drilling the hole to size and depth. The tip of the drill bit is ground off to prevent it from drilling deeper than the original hole. Lube the unthreaded portion of each hole with light oil like penetrating oil.<br><br> Retract the drill several times to help clear the chips from the drill bits flutes. Be careful not to force the drill after it reaches the bottom of the original hole depth. 4.<br><br> Blow out the metal chips using a long air nozzle that will reach to the bottom of the holes. 5. Figure 2 -- Using the 5/8-11 three-flute Plug Tap and the Tap Alignment Block, place the Tap Block over the hole to be threaded.<br><br> Hold the Tap Block firmly against the deck surface, this will pilot the tap perpendicular to the deck surface. Keep the tap lubricated with TAP ® MAGIC while cutting the new threads. You should blow out the chips created by the tap often so that the tap will not jam them into the bottom of the hole.<br><br> Failure to do so could cause the tap to break. *Note: The tap will cut slightly into the diameter of the head alignment pin bushing holes but not enough to effect the fit or alignment of the locating bushings when reinstalled. 6.<br><br> Figure 3 -- Using the 5/8-11 four-flute Bottom Tap, and the TAP ® MAGIC, tap the remainder of the hole depth, being careful not to over- tighten and break the tap at the bottom of the hole. *Note: This step may not be necessary if the insert installs to the correct depths described in step 7. Figure 4.<br><br> -6- 7. Figure 4 -- Blow out all chips from the hole. Clean the threaded hole and the insert with contact cleaner or brake cleaner.<br><br> Check the insert depth by installing an Insert using the "T" shaped installation tool provided in your kit prior to adding threadlock. Measuring from the top of the deck surface down to the top of the Insert as shown in Figure 4. Insure that the top of the Insert can be installed to the correct depths listed below.<br><br> Remove the Insert. Add a couple drops of threadlock to the newly threaded hole approximately ½" to ¾" from the deck surface. Add threadlock to the outside diameter of the Insert.<br><br> Install the Inserts with the installation tool,making certain the top of the insert installs to the correct depths shown in Figure 4 . Allow threadlock to set for six hours minimum before installing head bolts. INSERT DEPTHS FOR 4.0/4.6L NORTHSTARS: 93-99 UPPER AND LOWER BANK=1.125 d (28.5mm) 2000-2005 UPPER BANK=.81 inch (20.5mm) LOWER BANK= 1.5 inch (38mm) Note: Before repairing 2004-2005 Norhtstar engines, please read note on page 5.<br><br> * Time saving tip : After the first insert is installed to the correct depth, take a permanent marker and make a mark on the installation tool, flush with the deck surface (2000 thru 2005 Northstars have two different insert depths). This will save time when installing the remainder of the inserts to their correct depth(s). Note: When threading the lower bank holes in the 2000 through 2005 Northstars, it may be necessary to use an 11mm-12 point socket or a correct fitting 6 point socket to drive the taps to there final depth due to the length of the tap and the deeper depth of the lower bank holes.<br><br> 8.Insure there are no sharp edges protruding up from the newly threaded holes before installing the head gaskets and alignment bushings. Success of the NS300L " insert kit is based on the inserts being installed correctly and square to the deck surface. Stability of the aluminum engine block can also play an important part for a successful repair.<br><br> It is recommended that the inserts be installed by someone experienced in drilling and tapping holes. When installed correctly, customers have found that the NS300L " insert system has exceeded there expectations. *Please check for the latest GM-suggested torque specifications before tightening head bolts.<br><br> Improper torque can lead to thread failure. -7- USING THE OPTIONAL DRILL AND TAP ALIGNMENT JIG The optional drill and tap alignment jig is highly recommended to ensure proper alignment of the drill and tap, especially for those attempting this repair for the first time. If you already have the drill jig from the GM-approved cfirst repair kit d, it will not be necessary to purchase the optional drill jig since the drill bushing in the GM cfirst repair kit d is the same size as the drill in the NS300L" kit, you will only need the tap alignment block to thread the holes perpendicular to the deck surface.<br><br> If you are repairing an engine that had previously been repaired with the GM-approved cfirst repair kit d, the basic kit with the tap block will work fine for this application since the hole above the threads created from the step drill in GM's first repair kit is the same size as the drill in the NS300L" kit, and will work very well as a drill guide to drill out the remainder of the hole. 1. Figure 1A 3 Install the drill bushing into the jig block and snug it in place with the thumb screw located on the side of the jig.<br><br> Make sure the deck surface is clean. Mount the drill & tap jig with a good head bolt hole near the hole being repaired, using the spacer (see note below) and one of the original head bolts, but do not tighten. Center the drill bushing over the hole being repaired by install the locating pin through the drill bushing and into the top of the hole being repaired.<br><br> Hold locating pin down firmly so that the tapered end of the pin centers itself into the top of the hole, then tighten the jig in place being careful not to over tighten. Remove the locating pin. Note: the spacer is designed to be used either with the counter bored end up, or the counter bored end down depending on the engine being repaired.<br><br> For 93-99 Northstars, the counter bored end should be up for all holes. Since the 2000-2005 Northstars have two different depth holes, the counter bored end should be up for the lower bank holes, and down for the upper bank holes. 2.<br><br> Figure 2A- Drill hole following steps 3 & 4 on page 6. After you have drilled about 1½ d deep, you can remove the drill bushing then drill the remainder of the hole without it . This will allow for more chip clearance.<br><br> 3. Figure 3A - loosen the thumb screw and replace the drill bushing with the tap bushing (tap bushing has a larger hole diameter and a groove cut around the outside diameter). Follow steps 5 & 6 on page 6 for threading holes.<br><br> After you have threaded the hole about 1½ d deep, you can remove the jig from the deck surface. This will make it easier to clean out the chips when threading the remainder of the hole. 4.<br><br> Follow step 7 on page 7 for insert installation. -8-

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