How to measure angle when ratcheting a bolt?

Question

The torque spec for my Tacoma says that cylinder head bolts should be torqued (in a specific sequence) to 27 ft/lbs initially and then again each should be turned another 180 degrees in the same sequence.

I know how to use a torque wrench to set torque to a specific ft/lbs but I don't know how to measure the angle turned by ratcheting. How do I make sure that a certain number of clicks on a ratchet equates a certain angle?

As a bonus question, can you explain why Toyota would spec the second round of torquing in angles and not ft/lbs ? I think ft/lbs would be a cleaner spec.

Answer 1

90° = quarter turn. 180° = half turn. It's alright if you are off a few degrees.

I typically start with the breaker bar perpendicular (straight out) and do quarter turns, or have it straight off to the left. Just keep yourself parallel or perpendicular to where you start.

DO NOT USE A TORQUE WRENCH. It's bad for the torque wrench to turn after its clicked. Use a breaker bar.

These bolts are "torque to yield." They stretch out, which is why they should not be reused.

If you want to be precise you can use a Torque Angle Gauge.

Answer 2

I'm going to buck the other two answers and tell you

DO IT RIGHT OR DON'T DO IT.

It is very important to torque your head bolts correctly. The actual preferred method for attaining the proper torque is by figuring out the fastener stretch, not by using a torque wrench. When torquing, you are applying a clamping load on the object you are torquing. You can get this at its most accurate by measuring the stretch of the fastener by using a dial indicator. It's by far easier to torque the fastener down using a torque wrench and in most applications, this is an adequate method of doing things.

In your case it seems you are using torque-to-yield (T2Y) fasteners. These are (as @rpmerf pointed out) single use fasteners only (NOTE: If I could make this text blink, I would to emphasize the point). These must be replaced once you have broken them free (this would blink as well). If you don't, your head gasket will fail. The head gasket is the typical place for these types of fasteners. The reason these fasteners are only good for one go around is they are designed to go up to that "fail point", but not beyond. They start to fail by giving a bit or stretching. These are specific built fasteners by the manufacturer. They have done the stretch engineering for you. By applying the last degree turn, you are stretching the bolt to the tolerance they have engineered into the bolt. If you go past this point, you are only courting death for your engine. If you don't go far enough, you'll have a weak point in your torque chain which could allow for warpage in the part you are trying to affix ... especially true for a head.

As rpmerf stated, get the torque angle gauge:

Answer 3

Torque the bolt to the required torque. Then mark the head of the bolt with a marker or pen. This way you can visually check the angle. This is commonly used to ensure bolts are torqued during assembly.

Answer 4

If you don't have access to a torque angle gauge (as rpmerf recommends) or space is tight, here is one possible way estimate the angle with a ratchet:

• Find a ratchet that fits

• Without any socket on the ratchet, rotate the square drive head 180° by hand while counting the number of clicks felt.

  [My own 1/2"-drive ratchet clicks 36 times in a 180° sweep, so 5° per click]

• Install the socket and place the ratchet over the bolt and turn it in the opposite direction to simulate the maximum possible sweep. The idea here is to determine the number of clicks in a single pass.

  If the ratchet clicks less than two times per pass, the error is going to be too high to be able to rely on this method. Don't use it. Do not proceed.

  [If the sweep angle per pass is 15°, that'd be 2-3 clicks]

• If there are 2+ clicks per pass, calculate the number of passes needed to reach the total clicks in 180° and execute accordingly.

  [Assuming 36 clicks and 3 clicks per sweep, you're looking at 12 passes]

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Caveat

This approach can have high error associated with it. In the example above, one could be off by as much as 90°. The more clicks per sweep, the better the results will be with this approach.

Answer 5

i measured degree by using nail polish and white paper I painted two places on my socket, (the end of the socket is square), i first applied red nail polish down the length of the socket at corner of the square, then another down the length of the socket at the next corner of the square, then applied a small sliver of paper in the middle of each red line, then aligned the paper with the corners of the socket then added clear nail polish then need to tighten to 32 lbs then reverse one turn on all the bolts, then tighten to 22 lbs then 42 lbs then 62 lbs, what i found on head bolt torque on 1999 ford 3.0 Vulcan engine,