Engine Crack Repair: Pinning
If after inspection of the cast iron cylinder block or head a crack is found one of the easiest and safest methods of repairing this crack is pinning. Pinning is by far the most common method used for crack repair.
You can buy a pinning kit easily on the Internet; I found this one at Amazon.
Notice a pin is really nothing more than a bolt. The main thing is to buy a kit constructed of the same material as the part you wish to repair. This one is iron and it's important to note that aluminum is repaired using TIG or MIG welding. Pinning is typically done on iron cylinder heads and blocks. Here's how:
1. Always start at the ends of the crack. Take a punch and peen the crack or the ends for longer ones.
2. Drill a hole at one of the ends using the size bit that matches up with the bolt. These cracks usually reach all the way into a coolant or oil jacket. Be sure to drill deep enough to repair this leak.
3. I like to ream a ridge around the bolt hole before inserting the bolt. These pinning kits will have the proper tap but if not just match a tap from your set to the bolt and tap the hole created in step two.
4. Apply the thread lock or sealer provided in the kit and torque the bolt to around 50lbs.
5. Grind or cut the bolt close to the surface and then peen the bolt again with a punch and hammer.
6. Smooth the bolt even with the surface.
Sometimes it requires more than one bolt to repair a crack. To do this overlap the bolts and it's important to start at both ends and work your way to the middle. I usually overlap the bolts about 25% over each other.
Welding engine blocks is best left to the professional. Many people have messed up there heads trying to do this so I highly recommend pinning. Remember, an ounce of patience is worth a pound of cure. In other words if you take your time everything will come out just fine.
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