Why is 2nd round of head bolt torquing spec-d in angles and not ft/lbs ?

The spec says torque cylinder head bolts in a specific order first to 27 ft/lbs and then turn each in the same order another 180 degrees.

Why did they spec the second round in degrees and not ft/lbs? Since I do not have an angle gauge, can anyone approximate what that 180 degrees on top of 27 ft/lbs would convert to in ft/lbs ... a ballpark ?

 

No because it is set deep inside the head and also it is black so marking is kindof inconvenient

 

180* is half a turn.

Don't worry about the ft# reading. Just follow the instructions.

 

I understand that it is half turn but how do you measure that you went half turn when each pull you are moving rotationally only maybe 10-15 deg and that is not precise otherwise you could count ? keep in mind, the bolts are already on high torque, I can't just take a breaker bar and spin it freely 180...

 

27# is not high torque. You do lug nuts at 80 or 90, right?

Anyway, since you are not getting a reading, you actually can use a breaker bar.

Why not mark what you can see, which could even be where your extension fits the ratchet. Use that to eyeball your 180.

 

I was thinking the same but it's kindof inconvenient because the bolts are set so deep inside the heads. There is also

$19 OTC 4554 1/2" Drive Torque Angle Gauge

this tool.

 

I can only hope they will have it at Autozone so I can proceed with the job as opposed to having to order and wait for delivery ...

 

Sounds like your rebuild is coming along nicely.

 

Yes, I hope so. I cleaned the heads really nicely, cleaned the valves and lapped them. etc. but it's still too early to celebrate

 

only 27ft lbs + 180 * thats all the head bolts need? hmm might double check that.

Either way. Torque down to 27. Then mark the socket extension with a line, and do a 180... easy peasy.

 

interesting. I have never seen something like that before. I wonder what the final average torque is after 27 +180*

Couple of the motors i have done head bolts have been up around 120ish ftlbs!

I wonder for those fellows that have headgasket issues down the line... would torquing the head bolts down a lil more of helped?

 

That was part of my question, to approximate an apples-to-apples comparison and avoid acquiring the angle gauge.

 

you wouldnt need an angle gauge. Like stated simply mark the socket extension with a line, note where it lines up with something on the head, and keep ratcheting untill its spun 180*

 

Thanks. I will try that.

 

I hope you're doing all the bolts on the head at 27lbs according to the tightening order, then on the second trip around doing the 180 degrees.

 

Yes, that is exactly how I am doing it. I think I made that clear in the OP when I said "and then turn each in the same order another 180 degrees"

 

I got confused by your lack of commas if you completed the first pattern before starting the second round of tightening. My bad.

 

You go the 180 deg to finish streching the bolt, these are torque to yield bolts and can only be used once.