Question about cylinder head torque sequence...
02-19-2007, 10:42 AM
#16
Drive-by provocation guy
Rennlist Member
Rennlist Member
Join Date: Apr 2002
Location: NAS PAX River, by way of Orlando
Posts: 10,439
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Chris White
Technically – anything with a stock (fiber) type head gasket should be retorqued.
02-19-2007, 10:47 AM
#17
Addict
Rennlist Member
Rennlist Small
Business Sponsor
Rennlist Member
Rennlist Small
Business Sponsor
Originally Posted by toddk911
Chris: So stock is 65 but you suggest up to 80? Even with ARP?
02-19-2007, 01:07 PM
#18
Rennlist Member
This is an interesting thread in conjuction with the o-ringing thread.
I had my block o-ringed some time ago, for use with copper o-rings and a wide fire ring head gasket. I have the factory head studs
The shop recommended torquing the head, using the torque-angle method, letting it sit for 24 hours -then loosen the head nuts, and then retorque (anyone else heard or recommend loosening before the retorque?).
For the initial torquing sequence, the 90 deg was very close to the old 65 ft-lbs spec. However, after loosening, when I retorqued with the angle method, I could not come anywhere near the 90 deg angle, it would have been way too tight. Im assuming the the wide fire ring (fiber) gasket material, must have compressed with the initial torquing. So I should have used the ft-lbs spec instead.
I ended up with the nuts torqued to approx 80-85 ft-lbs, which I have been concerned about ever since (either over stretching the studs, or damaging the anchor threads in the block). But it sounds like 80-85, shouldnt be enough have damaged anything (?).
Thanks
I had my block o-ringed some time ago, for use with copper o-rings and a wide fire ring head gasket. I have the factory head studs
The shop recommended torquing the head, using the torque-angle method, letting it sit for 24 hours -then loosen the head nuts, and then retorque (anyone else heard or recommend loosening before the retorque?).
For the initial torquing sequence, the 90 deg was very close to the old 65 ft-lbs spec. However, after loosening, when I retorqued with the angle method, I could not come anywhere near the 90 deg angle, it would have been way too tight. Im assuming the the wide fire ring (fiber) gasket material, must have compressed with the initial torquing. So I should have used the ft-lbs spec instead.
I ended up with the nuts torqued to approx 80-85 ft-lbs, which I have been concerned about ever since (either over stretching the studs, or damaging the anchor threads in the block). But it sounds like 80-85, shouldnt be enough have damaged anything (?).
Thanks
02-19-2007, 04:15 PM
#19
Rennlist Member
Originally Posted by Laust Pedersen
Wouldn’t it be interesting to know what the actual clamping force is?
Actually it shouldn’t be too difficult to measure. Just cut out a piece of pressure sensitive film (ref.1 and ref.2), put it under the washer for the head nut, tighten the nut to your favorite torque or angle (making sure the washer does not rotate), remove the nut and film, translate to color of the film to stress and multiply by the area of the washer. That’s the clamping force of a single head stud.
Then it may be a good idea to divide by the cross-sectional area of the stud to get the stress and verify you are less than 90% of the yield strength of the stud.
With this data we can actually compare the different torquing methods and the influence of the gasket type.
I am getting a sample of the high pressure film. If anybody wants to try it out on a standard gasket with standard torquing procedure I can supply you with a sample (of a sample).
Laust
Actually it shouldn’t be too difficult to measure. Just cut out a piece of pressure sensitive film (ref.1 and ref.2), put it under the washer for the head nut, tighten the nut to your favorite torque or angle (making sure the washer does not rotate), remove the nut and film, translate to color of the film to stress and multiply by the area of the washer. That’s the clamping force of a single head stud.
Then it may be a good idea to divide by the cross-sectional area of the stud to get the stress and verify you are less than 90% of the yield strength of the stud.
With this data we can actually compare the different torquing methods and the influence of the gasket type.
I am getting a sample of the high pressure film. If anybody wants to try it out on a standard gasket with standard torquing procedure I can supply you with a sample (of a sample).
Laust
So, once we have that force for a single stud, we multiply it by 10 (all the head studs). That would be total clamping force.
