Street News

Before you junk it, read this!

Engine blocks are tough. They deal with thousands of pounds of force pulling in every which way thousands of times a minute for hundreds of thousands of miles. Add to that the searing temperatures and constant RPM changes and heavy loads subjected to these cast iron hulls, it is quite amazing they work at all. The problem is, sometimes they don’t. Get it too hot and things start to warp, too cold and the water inside them can freeze. Eventually, this leads to failures such as cracks. An engine block can crack just about anywhere, but the results are the same- it is junk. Or is it?

advertisement for Steeroids

If you do some research and listen to some of the old-timers, repairing cast iron can be done, but it is not easy. Welding cast iron takes serious skill, tools and long-forgotten techniques. The part to be welded must be preheated before welding and allowed to cool very slowly, otherwise the repair will just crack out again or worse, shatter. Stick Welding cast iron hardens the metal, so the surrounding metal remains soft. This creates a whole other host of problems, as the soft metal will fatigue where the harder metal is, failing again. There is a technique called Flame Spray welding which literally uses powdered metal and a blowtorch to melt the powdered metal to the cast iron. It is a tricky technique to learn and not many facilities offer this service anymore, but when done right it works.

You could always use an epoxy like JB Weld, as the package certainly says it is capable. In our experience, the stuff really does work, but would you want to trust the repair of a rare engine block with a $5 epoxy? There is another solution and the original principle has been around since cast iron itself. It is called pinning and it works.

There are several versions of pinning; smooth dowel-style pins (the original version), the home-brewed bolts and screws method, and the modern version called Lock-n-Stitch. The smooth dowel pins require drilling holes in the crack, tapping in brass or steel pins and then peening the ends to seal them. This is tricky to accomplish and takes some practice to master. This is the way it was done from the very beginning. Since pinning is so tricky, many of the old-timers modified the method by using bolts and screws to do the same thing, except the pins were held in with threads. The problem with this method, as well as the dowel method, is that this puts outward stress on the metal, which can further spread the crack, and if you have lost a section of block, forget about replacing it. Using these repair methods on anything other than a relative low-stress area will likely result in further failure.

Gary Reed, owner of Lock n Stitch, developed a new, modern approach to cast iron repairs. Based on the traditional method of pinning and stitching, the Lock n Stitch (or LNS for short) uses specially designed threaded pins to seal cracks and breaks in cast iron. The patented thread design actually pulls the metal together rather than spread it apart. This allows the LNS method to do things never before thought possible. LNS pins are commonly used to replace entire sections of engine block, piecing in plate steel to cast iron. In fact, the LNS method was used to repair the cast-iron dome on the US Capital building, which weighs in at over 9 million pounds. Had Pass and Stow had LNS pins, the Liberty Bell would still be ringing.

What this means for you is that should the motor in your 396 SS Camaro Pace Car convertible crack, you can fix it. High-stress areas like a broken main web can be repaired; the LNS pins will not fail if properly installed. The LNS website has examples of LNS pins in use in massive machinery that must withstand hundreds of thousands of pounds of force. The best part is that you can do it yourself.

We discovered this product after bringing home a ’69 383 Chrysler High-Performance coded motor for a street-strip project. Once we got it in the shop, we found a section inside the lifter valley that had been treated to a grinder. Upon further inspection, we found a 4-inch long crack. The block was purchased at a good price and since wasting money is never good, we looked for a repair solution. After we regained consciousness from our sunken hearts, the research began and we happened upon LNS. A few calls were made and we had our plan- fix it with Lock N Stitch pins in our shop.

The process sounds harder than it is- locate the crack and mark it (We used the SpotCheck kit from Maganflux), drill a hole in the block, countersink the hole, tap the hole with a special tap, insert the pin, and then drill another hole right next to the first, while overlapping the first pin, and repeat. In other words, this seems like it is going to take forever, cause a real headache and be very frustrating. Once we got into it, it was really easy. LNS provides a spacing jig that allows you to set a series of holes that are fully prepped and pins inserted, then you drill the holes that run between them to complete the task. In three hours, we repaired a 4-inch hole using 26 pins, from start to finish. Once the drilling and pinning is completed, the repair is ground flush and you even use a needle scaler to replicate the original finish so it looks like there was never even a repair made. If the repair is to be made in an oil or water galley, it should be pressure tested before being put back into service. You can even repair the cylinder walls using this technique, as these repairs can be machine bored and honed. LNS stitches are the best way to repair a cracked cylinder head or valve seat.

The possibilities with LNS are almost limitless. There are several types of LNS pins, and they can be used on any type of metal, including aluminum. This is a real solution to a problem that many restorers and hobbyists have faced. It really works and is much less expensive than the less-reliable Flame-Spray method. Lock n Stitch is available in separate components or in kit form, which is what we used. The kit provided the drill bits, taps, pins and even the liquid sealant (similar to thread lock) and tapping fluid. For about what the scrap yard would pay for a junk block, we fixed our 383 in just a few hours. Just think of the possibilities. How many times have you passed on a rare motor or cylinder heads at a swap meet because of a crack?

When we got the engine home, we found the lifter galley had been hit with a grinder, likely to cover up this crack. It is hard to see with the naked eye, but It’s there.

When we got the engine home, we found the lifter galley had been hit with a grinder, likely to cover up this crack. It is hard to see with the naked eye, but It’s there.

To make the entire crack visible, we used a non-destructive testing method from Magnaflux called SpotCheck. This method works on ferrous and non-ferrous materials, even plastic. The first step is to clean the surface using the supplied cleaner.

To make the entire crack visible, we used a non-destructive testing method from Magnaflux called SpotCheck. This method works on ferrous and non-ferrous materials, even plastic. The first step is to clean the surface using the supplied cleaner.

Once the surface was clean, we sprayed on the penetrant which needs to sit at least 10 minutes. We let it sit for 15 so we would get good penetration. After that, we buffed it off. Sometimes you need a rag with some cleaner on it to get the penetrant off.

Once the surface was clean, we sprayed on the penetrant which needs to sit at least 10 minutes. We let it sit for 15 so we would get good penetration. After that, we buffed it off. Sometimes you need a rag with some cleaner on it to get the penetrant off.

Next, the developer was sprayed on. This stuff is very sensitive, only light mist is required. Large cracks so up instantly, smaller cracks take some time to show up.

Next, the developer was sprayed on. This stuff is very sensitive, only light mist is required. Large cracks show up instantly, smaller cracks take some time to show up.

White area is where the developer dried. The Spotcheck materials have been drying for about an hour at this point, so it had bled to the surrounding area. We marked the crack with a paint marker, then buffed off the surface.

White area is where the developer dried. The Spotcheck materials have been drying for about an hour at this point, so it had bled to the surrounding area. We marked the crack with a paint marker, then buffed off the surface.

The first step in the LNS process is drilling the end. Using the supplied bit for our kit, the end of the crack was drilled. You do not want to use a corded drill for this, which is too powerful and will end up breaking drill bits. An air-powered drill is the best choice here, as a cordless drill will be too heavy and can bend or break bits too.

The first step in the LNS process is drilling the end. Using the supplied bit for our kit, the end of the crack was drilled. You do not want to use a corded drill for this, which is too powerful and will end up breaking drill bits. An air-powered drill is the best choice here, as a cordless drill will be too heavy and can bend or break bits too.

The hole must be countersunk for the shoulder of the pin. The block is very thin here, just over a 1\4-inch. 3\16” is the minimum thickness for these pins to work, so we used the supplied drill stop and set the depth to 1\3rd of the shoulder depth, the minimum allowable.

The hole must be countersunk for the shoulder of the pin. The block is very thin here, just over a 1\4-inch. 3\16” is the minimum thickness for these pins to work, so we used the supplied drill stop and set the depth to 1\3rd of the shoulder depth, the minimum allowable.

Slow and steady wins the race with this process. Cutting too fast will dull the bit, which can’t be resharpened at home. We used a cordless drill.

Slow and steady wins the race with this process. Cutting too fast will dull the bit, which can’t be resharpened at home. We used a cordless drill.

Using a cordless drill, the hole was tapped using the special tap and cutting fluid supplied in the kit. A cordless drill is the best solution for speed and ease of use.

Using a cordless drill, the hole was tapped using the special tap and cutting fluid supplied in the kit. A cordless drill is the best solution for speed and ease of use.

The pin installs with a socket, and once the correct torque is applied, the head just snaps off, this could not be simpler. That said, if you countersink too far, you run the risk of stripping the threads.

The pin installs with a socket, and once the correct torque is applied, the head just snaps off, this could not be simpler. That said, if you countersink too far, you run the risk of stripping the threads.

The hard part is drilling the next pin. The instructions suggest that beginners use the single pin method, which is shown here, installing one pin after another. We found this difficult.

The hard part is drilling the next pin. The instructions suggest that beginners use the single pin method, which is shown here, installing one pin after another. We found this difficult.

The kit came with a spacing jig. We inserted the jig into the second hole and started drilling. This is the more precise method and we found it easier to do.

The kit came with a spacing jig. We inserted the jig into the second hole and started drilling. This is the more precise method and we found it easier to do.

We drilled each hole to cover about half of the crack. We did not fully drill each hole, but made dimples. We came back and fully drilled each hole afterwards.  Then each hole was counter sunk and tapped.

We drilled each hole to cover about half of the crack. We did not fully drill each hole, but made dimples. We came back and fully drilled each hole afterwards. Then each hole was counter sunk and tapped.

Before the pins were installed, we used a cleaning brush to clean out the holes. You don’t want any junk in there.

Before the pins were installed, we used a cleaning brush to clean out the holes. You don’t want any junk in there.

This is what the counter sunk holes look like. You can see the threads and how cutting too deep would be a problem.

This is what the counter sunk holes look like. You can see the threads and how cutting too deep would be a problem.

Each hole needs a little thread locker. This acts to lock the threads in place and provide a little extra seal.

Each hole needs a little thread locker. This acts to lock the threads in place and provide a little extra seal.

Once the pins are installed, drilling the center holes is tricky. We broke one bit drilling two holes, so we had to re-think our process.

Once the pins are installed, drilling the center holes is tricky. We broke one bit drilling two holes, so we had to re-think our process.

We used a flame-tip carbide (part of a kit we sourced from the Eastwood Company) and an die-grinder to cut the center where each pair of pins meet. This took the catch points out of the equation and the drilling was easy.

We used a flame-tip carbide (part of a kit we sourced from the Eastwood Company) and a die-grinder to cut the center where each pair of pins meet. This took the catch points out of the equation and the drilling was easy.

Each hole was countersunk (you have to adjust the drill stop since the pin shoulder are higher than the block surface), tapped and pins installed. You can see how each pin interlocks with the other.

Each hole was countersunk (you have to adjust the drill stop since the pin shoulder are higher than the block surface), tapped and pins installed. You can see how each pin interlocks with the other.

The other half of the crack was pinned in the same manner. This is almost the end, but not quite.

The other half of the crack was pinned in the same manner. This is almost the end, but not quite.

Using a ball peen hammer, each pin was tapped to help seal the threads. Only tap the edges and not the center.

Using a ball peen hammer, each pin was tapped to help seal the threads. Only tap the edges and not the center.

Then we used a grinder to grind the pins flush.

Then we used a grinder to grind the pins flush.

The finished repair looks good, but we need to test it.

The finished repair looks good, but we need to test it.

Using a piece of plexiglass (we have bunch lying around, but you can use steel or thick aluminum) we made a plate to seal the water pump openings. We used a shrader-valve fitting from our Summit Racing AN fitting test kit. The plate was sealed with clay. This allows us to pump air into the water jackets. The block was sealed with foam rubber and the cylinder head installed, and hand torqued.

Using a piece of plexiglass (we have bunch lying around, but you can use steel or thick aluminum) we made a plate to seal the water pump openings. We used a shrader-valve fitting from our Summit Racing AN fitting test kit. The plate was sealed with clay. This allows us to pump air into the water jackets. The block was sealed with foam rubber and the cylinder head installed, and hand torqued.

The block was pressurized with 30 psi and the repair sprayed with soapy water. Most of the repair held but we had three areas that developed leaks.

The block was pressurized with 30 psi and the repair sprayed with soapy water. Most of the repair held but we had three areas that developed leaks.

Using a ball peen hammer or a small punch and hammer, we tapped the leaky areas, peening them some more. It took a few tries, but we got them all sealed. This is a great method of repairing an otherwise good engine.

Using a ball peen hammer or a small punch and hammer, we tapped the leaky areas, peening them some more. It took a few tries, but we got them all sealed. This is a great method of repairing an otherwise good engine.

About Jefferson Bryant (196 Articles)
A life-long gearhead, Street Tech Magazine founder and editor Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 5 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced. You can follow Jefferson on Facebook (Jefferson Bryant), Twitter (71Buickfreak), and YouTube (RedDirtRodz).

Leave a comment

Your email address will not be published.


*