cylinder head torque down
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texasSlick
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Update on Reply #5 above.
A second month has passed since I torqued my Atlas head bolts, without starting the engine.
After the first month, I found most of the bolts required some additional "twist" to come up to the target torque value 25 ft. lbs (see Reply #5). This suggested the gasket was "settling in" due to time and clamp pressure, without any heat cycling. Now, after a second month, I checked torque again.
I first marked the four bolts near the spark plugs with alignment marks. Then, using the "over the top" method I applied 25 ft lbs and found both bolts on the right cylinder moved slightly. The bolts on the left cylinder did not move, I then loosened and re-torqued the left cylinder bolts and found both bolts came exactly back to the alignment marks.
The remaining bolts or nuts could not be alignment marked, so using the over the top method, I checked if I could detect any movement. Of the six remaining bolt/nuts, three moved slightly. I loosened and re-torqued the other three, attempting to estimate if the wrench moved beyond the initial point, but this was too subjective to yield any information.
I estimated the right cylinder bolts moved 4 - 5 degrees each. This was done by measuring the distance between alignment marks (0.025"), dividing by the radius of the bolt head (0.30"), and using trigonometry to find the inverse tangent. Not at all precise, but I think it is a good estimate. FWIW, I estimate that the nuts which moved, moved about the same 4 - 5 degrees.
These results strongly suggest the gasket "flows" (the metallurgical term is thermoplastic deformation) by the action of time and clamp pressure alone. Heat cycling can be expected to increase this effect.
Since the movement of the bolts and nuts was very much less after two months as compared to that of the first month, the gasket is coming into a stable condition.
I do not intend to repeat this test after three months ..... I am ready to crank her up!
Slick
A second month has passed since I torqued my Atlas head bolts, without starting the engine.
After the first month, I found most of the bolts required some additional "twist" to come up to the target torque value 25 ft. lbs (see Reply #5). This suggested the gasket was "settling in" due to time and clamp pressure, without any heat cycling. Now, after a second month, I checked torque again.
I first marked the four bolts near the spark plugs with alignment marks. Then, using the "over the top" method I applied 25 ft lbs and found both bolts on the right cylinder moved slightly. The bolts on the left cylinder did not move, I then loosened and re-torqued the left cylinder bolts and found both bolts came exactly back to the alignment marks.
The remaining bolts or nuts could not be alignment marked, so using the over the top method, I checked if I could detect any movement. Of the six remaining bolt/nuts, three moved slightly. I loosened and re-torqued the other three, attempting to estimate if the wrench moved beyond the initial point, but this was too subjective to yield any information.
I estimated the right cylinder bolts moved 4 - 5 degrees each. This was done by measuring the distance between alignment marks (0.025"), dividing by the radius of the bolt head (0.30"), and using trigonometry to find the inverse tangent. Not at all precise, but I think it is a good estimate. FWIW, I estimate that the nuts which moved, moved about the same 4 - 5 degrees.
These results strongly suggest the gasket "flows" (the metallurgical term is thermoplastic deformation) by the action of time and clamp pressure alone. Heat cycling can be expected to increase this effect.
Since the movement of the bolts and nuts was very much less after two months as compared to that of the first month, the gasket is coming into a stable condition.
I do not intend to repeat this test after three months ..... I am ready to crank her up!
Slick
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