head bolts stretch or not?
#31
08-22-2012, 01:31 PM
Baja
The different length is just because they are going through different thicknesses of cylinder head.
They could be wrong, but they look ok to me. You always start from the middle and work outward, alternating right and left of center. though I could see flipping 8 & 9 on the 10 bolt heads.
Please post link if you find it.
They could be wrong, but they look ok to me. You always start from the middle and work outward, alternating right and left of center. though I could see flipping 8 & 9 on the 10 bolt heads.
Please post link if you find it.
#32
08-22-2012, 02:04 PM
Recovery Vehicle
The different length is just because they are going through different thicknesses of cylinder head.
They could be wrong, but they look ok to me. You always start from the middle and work outward, alternating right and left of center. though I could see flipping 8 & 9 on the 10 bolt heads.
Please post link if you find it.
They could be wrong, but they look ok to me. You always start from the middle and work outward, alternating right and left of center. though I could see flipping 8 & 9 on the 10 bolt heads.
Please post link if you find it.
Im having a b!tch of a time finding it. It was one of those things where I was searching for something totally different, saw an unrelated interesting thread and read it. Then, I didnt bother bookmarking because I figured it would be easy to find again.
*sigh*
#33
08-22-2012, 02:37 PM
The OE head bolts aren't torqued, other than in the first step, and they are lubed so there's little galling. After that they are turned to 90 + 90 degrees and galling isn't a factor.
If using other bolts that are torqued, then there are torque tables to adjust for material types, dry vs lubed, etc.
If using other bolts that are torqued, then there are torque tables to adjust for material types, dry vs lubed, etc.
Very impressive that you state "galling is not a factor". Care to back that up with, well, anything that states it is not a factor, and then explain what factors are present?
#34
08-22-2012, 02:40 PM
Baja
But even if it were the case I can't think of how you'd know what angle to use, unless you measure the bolt length and turn the longer ones more by the same percentage difference. Or the short ones less, but which is correct?
#35
08-22-2012, 04:33 PM
Recovery Vehicle
This isnt it, but it is similar. Posts by Trevor2
Range Rover 4.6 Head Gasket Replacement - Land Rover Zone
If you torque all the bolts to a specified torque for that size of bolt (old school) you know, that every bolt has exactly the same clamping force. If you turn a bolt through 90deg & 90deg again there is no way you can guarantee that all the bolts are exactly at the same (clamping force) because the dial gauge you are turning with, as a human being you will never get them all the same, however with the click of a calibrated torque wrench you will.
I have discussed this with some engine re-manufactures who rebuild engines all day long & they use the torque method, why, because sometimes at their cost without a torque wrench to regulate the tightening, a bolt as damaged a cylinder head & or pulled the threads on the block, old school vers. new school. the argument will never be settled.
Range Rover 4.6 Head Gasket Replacement - Land Rover Zone
If you torque all the bolts to a specified torque for that size of bolt (old school) you know, that every bolt has exactly the same clamping force. If you turn a bolt through 90deg & 90deg again there is no way you can guarantee that all the bolts are exactly at the same (clamping force) because the dial gauge you are turning with, as a human being you will never get them all the same, however with the click of a calibrated torque wrench you will.
I have discussed this with some engine re-manufactures who rebuild engines all day long & they use the torque method, why, because sometimes at their cost without a torque wrench to regulate the tightening, a bolt as damaged a cylinder head & or pulled the threads on the block, old school vers. new school. the argument will never be settled.
#36
08-22-2012, 04:57 PM
Recovery Vehicle
Found it! 
This is actually not where I read it the first time, but it is the same. Written by DWebber Chongo.
head gaskets and bolts - Land Rover and Range Rover Forums
Head bolts must be replaced every time you remove the head, they are not regular bolts, but a special designed stretch bolt. Their is a tightening sequence principle that must be followed although contrary to popular belief, and the service manual, as long as the principle is adhered to the sequence can be changed. The principle is uniformly and incrementally tightening the head down. The actual order doesn’t matter. In testing the book vs. torque standards I found the service manual, “again” in error as it says to tighten all bolts to 15 ft. lbs. then 90 degrees more in sequence, then a additional 90 degrees for final torque. This is bogus, and utter nonsense. My findings after doing this left the 3 long head bolts at 50 - 58 foot pounds of torque, while the short head bolts read 68 - 72 foot pounds of torque. I found that almost an additional 90 degrees was required on the long bolts for a total of 245 - 270 degrees before the long bolts achieved the 68 - 72 foot pound equivalent to the short bolts. This makes the tension and torque on all bolts even. Due to the dissimilar materials of the steel bolts and aluminum heads it needs a stretch bolt design. Don’t go buying studs for this engine, you won’t be happy with the long term effects.
What I do is Torque every head bolt the way the book says, then I use a torque wrench and run them all up to the highest torque setting. If that's 65 ft, lbs on your torque wrench then put them all at 65. But since these are stretch bolts, Please do the two 90 degree increments first, then check a couple of the short bolts to see what torque is on them, then tighten the long ones to the same setting. what this does is even the pressure among all bolts, and places even torque on all portions of the head gasket.
DiscoMike basically b!tchslaps his theory a couple posts later, but food for thought...
This is actually not where I read it the first time, but it is the same. Written by DWebber Chongo.
head gaskets and bolts - Land Rover and Range Rover Forums
Head bolts must be replaced every time you remove the head, they are not regular bolts, but a special designed stretch bolt. Their is a tightening sequence principle that must be followed although contrary to popular belief, and the service manual, as long as the principle is adhered to the sequence can be changed. The principle is uniformly and incrementally tightening the head down. The actual order doesn’t matter. In testing the book vs. torque standards I found the service manual, “again” in error as it says to tighten all bolts to 15 ft. lbs. then 90 degrees more in sequence, then a additional 90 degrees for final torque. This is bogus, and utter nonsense. My findings after doing this left the 3 long head bolts at 50 - 58 foot pounds of torque, while the short head bolts read 68 - 72 foot pounds of torque. I found that almost an additional 90 degrees was required on the long bolts for a total of 245 - 270 degrees before the long bolts achieved the 68 - 72 foot pound equivalent to the short bolts. This makes the tension and torque on all bolts even. Due to the dissimilar materials of the steel bolts and aluminum heads it needs a stretch bolt design. Don’t go buying studs for this engine, you won’t be happy with the long term effects.
What I do is Torque every head bolt the way the book says, then I use a torque wrench and run them all up to the highest torque setting. If that's 65 ft, lbs on your torque wrench then put them all at 65. But since these are stretch bolts, Please do the two 90 degree increments first, then check a couple of the short bolts to see what torque is on them, then tighten the long ones to the same setting. what this does is even the pressure among all bolts, and places even torque on all portions of the head gasket.
DiscoMike basically b!tchslaps his theory a couple posts later, but food for thought...
#37
08-22-2012, 05:49 PM
Baja
Certainly interesting perspectives. This is my take.
Yes, using an angle meter can be difficult as it can be hard to read the dial and turn the wrench at the same time. That's why I had my wife watch the dial and tell me as soon as I got to the 90 degrees. The manual says +/- 5 degrees over the 180, so +/1 2 1/2 degrees per step so there's a bit of leeway.
It's generally agreed that a click type torque wrench isn't as accurate as a beam style for very critical torques because when the wrench clicks it's nearly impossible to not continue to the stop and add a bit more torque.
On the tightening sequence, it's possible the random torque values are a result of random tightening sequence. I don't think you'll find many engineers who will agree that when tightening a large assembly that needs to seal that the order doesn't matter. 99% will say from the center out.
Torque is the resistance to turning and is measured when the bolt or nut is turning. It's going to be a different value if you measure it when it's static. i.e., if you torque a bolt to 100lb-ft and stop, then put a torque wrench on it, it's going to move until you exceed 100lb-ft by a significant amount. So if you check a head bolt and it doesn't move until you apply say, 110lb-ft, and then you torque the others to 110, they will take even more than 110 to move again, so where do you stop?
Yes, using an angle meter can be difficult as it can be hard to read the dial and turn the wrench at the same time. That's why I had my wife watch the dial and tell me as soon as I got to the 90 degrees. The manual says +/- 5 degrees over the 180, so +/1 2 1/2 degrees per step so there's a bit of leeway.
It's generally agreed that a click type torque wrench isn't as accurate as a beam style for very critical torques because when the wrench clicks it's nearly impossible to not continue to the stop and add a bit more torque.
On the tightening sequence, it's possible the random torque values are a result of random tightening sequence. I don't think you'll find many engineers who will agree that when tightening a large assembly that needs to seal that the order doesn't matter. 99% will say from the center out.
Torque is the resistance to turning and is measured when the bolt or nut is turning. It's going to be a different value if you measure it when it's static. i.e., if you torque a bolt to 100lb-ft and stop, then put a torque wrench on it, it's going to move until you exceed 100lb-ft by a significant amount. So if you check a head bolt and it doesn't move until you apply say, 110lb-ft, and then you torque the others to 110, they will take even more than 110 to move again, so where do you stop?
#38
08-23-2012, 07:29 AM
ARP head bolts
Call mark at D&D and he knows the right torq for ARP studs. I got mine from him and he sent me instructions for them. If i remember it was not near 80 FT LBS... But it's been over a year and cant remember...
D&D Fabrications: Engineering & Fabrication Services
D&D Fabrications: Engineering & Fabrication Services
#39
08-23-2012, 08:24 AM
Baja
On the engine I'm doing now I'm using the OE torque to yield head bolts. I torqued them to 20nm per the manual usiing a beam type torque wrench, then 90 and 90 using a long handle ratchet with an extender on the handle.
I have another engine to do so I if I remember I'll torque the 90 and 90 using a beam torque wrench and see what the torque value is when I get to 90 degrees.
I have another engine to do so I if I remember I'll torque the 90 and 90 using a beam torque wrench and see what the torque value is when I get to 90 degrees.
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