by Jim Rosengarth
A common problem experienced by heavily used performance engines is loose header bolts. This is caused mostly by the expansion and contraction of the heads coupled with engine vibration, which causes the header flange bolts to sometimes loosen and back-out. There are a couple ways to deal with this, including special locking washers, but the best way to ensure the bolts stay put is to safety wire them together.
Safety Wiring Technique
Safety wiring allows you to join two or more bolts to one another so that if one bolt starts to come loose, it's rotation will begin to tighten the bolt it is connected to via the safety wire. It is a simple concept that has been used in aviation since before WWII. In the drawing below, both bolts use a right-hand thread, so the counterclockwise (loosening) rotation of one will cause the other to rotate clockwise (tightening).
The bolts used for safety wiring have a hole drilled through the head for the safety wire. Any bolts can be drilled, in fact drilling jigs can be made or bought, however the extreme time and painstaking tedium of drilling 1/16" holes through hard stainless steel bolts (usually 16 of them) is not something I would see as time well spent. Fortunately, ARP makes several header bolt kits, like the one above, with drilled head bolts and washers included for as little as $40. The ARP bolts have the benefit of having two holes drilled through the head, so that no matter how the head lines up once tightened one hole will be easily accessible.
The wire used is usually stainless and must be small enough to fit through the hole in the bolt head. More importantly, the wire is annealed which softens it and allows it to be bent more easily. The holes in the ARP bolts are .050", so I am using .041" wire. Safety wire can be purchased from auto parts suppliers like Summit, Jegs, or from hardware suppliers like McMaster-Carr or MSC.
How to do it
To begin, install the headers and torque all of the bolts to specification. Work with the bolts for one primary at a time. Cut a piece of safety wire about 18-20 inches long and start with the bolt to the left of the primary. Run the wire through the hole in this bolt, wrapping the wire coming out closest to the bottom of the bolt clockwise around the bolt head. Then wrap this wire around the one coming out the top of the bolt head in a right hand direction. Continue twisting the wire clockwise to combine the two pieces.
Keep measuring the length of the twist over the primary as you get closer to the other bolt. Your goal is to enter the hole in the second bolt from the bottom and come out the top with one if the pieces of wire in the twist. The twist should end just at the bottom hole in the second bolt once pulled tight with a pair of pliers. Make sure that the twist over the primary is tight and can't be lifted off the primary tube. If it is, the twist is too long, so unwrap a turn at a time and try again.
Bring the second wire around the bolt head counterclockwise, and secure it over the wire coming out the hole with a LEFT hand turn. This will keep the second wire from popping off the bolt head.
Finally, continue the left hand twist until you have about an inch, and then cut the twist, keeping at least 4-5 turns, and tuck this pigtail back towards the intersection of the primary tube and the header flange. This will help prevent getting your hands cut up when changing spark plugs.
Conclusion
One thing I never mentioned was the use of safety wire pliers. Why? I don't use them. If you had to do several sets of headers a day, then it might be worth the $50-$60 to buy a pair, but not for the average shadetree mechanic. I did both headers by hand, using a pair of regular pliers just for pulling wire throught the holes and a pair of wire cutters, and it only took about half an hour. To me, this is cheap insurance for not having to deal with loose header bolts.
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