Use New Head Bolts In Your Rebuilt Engines
How much pressure is exerted on a head bolt? In a typical V8 engine, peak combustion pressures could be around 1,100 psi, which means each cylinder exerts about 14,000 lbs. of pressure on the cylinder head at full throttle. In fact, each head bolt may have to handle more than five tons of force!
Lift off force is the clamping load that is required to keep the head sealed under conditions that may be three times higher than the peak force exerted on the head. This could be up to 3,800 lbs. per bolt, with high performance and diesel applications being even higher!
Head bolts are designed to stretch as much as .006? to .010? or more, depending on the application, so replacing them when you assemble an engine is a good idea even if it is not required.
Torque-to-Yield (TTY) head bolts are used on many modern engines, especially engines with aluminum heads. A TTY bolt will stretch and then spring back to its original length only up to its yield point. This requires the bolt to be replaced after one use.
As a rule one must clean the threads in the block and use motor oil on the threads before installation. The torque specifications are based on oiled threads, not dry. Typically 10-30 multi-viscosity oil is used, and don’t forget to make sure your torque wrench is accurate, and use new head bolts with every rebuilt engine.
Rear Main Thrust Bearing Clearance
I grind quite a few small block Chevrolet crankshafts, and I know it’s easy for some of us to overlook the rear main thrust bearing clearance. What I do is keep a new spare thrust bearing on the crankshaft grinder, and prior to grinding I can do a quick check of the clearance. Another fact is that some of these cranks are on their second go around and I’ve occasionally found a few that were already ground for an oversize thrust width. It only takes a few seconds, and may avoid a comeback later on.
Shake Well Before Using
I was talking to a Valvoline motor oil engineer a few years ago about the decrease of zinc in today’s oils and he gave me a good tip. He told me to shake the bottle before pouring it into the engine. Some ingredients such as zinc and moly will settle to the bottom of the bottle over time just like the heavier particles in your orange juice settles. If you use brands that have light colored plastic bottles such as Lucas or Shell Rotella, you can see “pepper” looking particles at the bottom of the bottle. That’s the good stuff!
Jeff “Beezer” Beseth
Beezer Built Inc.
More Than One Use
A set of transfer punches has many uses in an engine shop. Besides their use as transfer punches, they also work great for removing hollow dowel pins. Simply insert the largest punch that will fit to prevent collapsing the dowel pin. Then clamp a set of vise grips on the outside and twist the dowel out without damage. Transfer punches also work great for straightening out already damaged hollow pins. Transfer punches will work as an aligning pin too.
Broken Tap, Aluminum Head: What To Do?
Recently a Mercedes 300SL Roadster came in requiring the removal of the intake and exhaust manifolds. When inspecting the bolt holes I found a broken tap.
It appeared the tap had been compressed when the bolt was installed. This was not good news on a $6,000 cylinder head!
I visited the hardware store and purchased several grinding stones, long, short, tapered, and cylindrical. In about 30 minutes I had the tap ground away. The flutes of the tap made a perfect place to start grinding. Eventually the center of the tap was ground away and the cutting teeth came out with needle nose pliers.
I found that the tap had broken in the remains of the stud deep in the hole. I used a Dremel tool to center in the broken stud, and then drilled it out as you would normally remove a broken bolt. Running a tap in the hole cleaned up the threads and I was able to install a new stud in about an hour.
The biggest problem I found was the grinding stone shanks were too short to go all the way in the hole. I used 6-7 stones to do the job.
A Light On The Subject
Having a bright light shining on your machine is a must. Attaching fluorescent lights to your crane provides lots of clean light on any casting that you might be lifting. An extra benefit is the ability to swing your light over a machine during machining operations to provide extra light and it allows the operator to swing the light left and right to eliminate shadows that are cast by other methods. These lights were attached to the sides of a dual mount hoist system with the electric cable sharing the rollers with the air line.
Marlar’s Machine Shop
Yates Center, KS
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