Intake & exhaust manifold torque

A

aermotor

Well-known member
I had problems with intake manifold leaks - two tries replacing the gasket in order to stop intake leak. The thought came to me that maybe there is a preferred torque sequence. I torqued progressively 25, 30, 35, 40 and final 45 lbs. on 4,2,3,1 studs. Any comments appreciated.

John
 
One thing to check for is if you're using torque on the studs to correct for the two manifolds not being perfectly flat and aligned. If they're out of spec then no amount of torque is going to correct it.
 
Chances are that if not sealing, the surfaces on the two manifolds are not even or the surface on the block is pitted. If the two surfaces on the manifolds are not even, good chance of cracking one when you get too tight. Are you using the rings in the exhaust? Does the exhaust have any droop? What gasket type are you using? I just get them tight and after a heat cool cycle, check again. Has the exhaust been separated from the intake or is the exhaust new? I know you said intake, but could be a combination of things not allowing the two parts to seat correctly. How did you check for intake leak and do you have the gasket between the carb and intake?
 
johnneilson said:
Same size thread as head stud into same block materials
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Yeah, but the 45 ft-lb torque is being applied to the nuts on the studs, not to the studs in the block. And the nuts are brass, not Grade 8 steel. And there are concave washers under the nuts. It's not analogous.
 
alexiskai said:
Yeah, but the 45 ft-lb torque is being applied to the nuts on the studs, not to the studs in the block. And the nuts are brass, not Grade 8 steel. And there are concave washers under the nuts. It's not analogous.
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correct, IF using brass nuts and concave washers.

Typically when they don't seal the hardware is replaced with higher grade hardware.

John
 
Assuming all of the above comments have been considered my question is still - is there a recommended sequence. Certainly going to full torque at any value you are comfortable with, I feel sure that alignment with the "flats" will be compromised by going to full torque on the first stud tightened while the others are "finger tight", especially with a thick copper crush gasket. Consider the torqueing procedure for the head and it is solid one piece with a thick copper gasket. Is my concern clear and does it have merit?

John
 
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I always thought that you start with the middle studs and work out, doing all of the studs a little bit at a time until you hit 35#.
 
old31 said:
I always thought that you start with the middle studs and work out, doing all of the studs a little bit at a time until you hit 35#.
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This is the kind of answer I am looking for and it makes sense to me but is there any way to verify that it is correct?

John
 
old31 said:
I always thought that you start with the middle studs and work out, doing all of the studs a little bit at a time until you hit 35#.
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I agree starting in the middle working out several steps on the torque. Like torquing a head middle out, I will add use some anti-seize on the threads
 
I just installed a new Snyders exhaust. No intake available, so I used my old one and had the flatness machined. I tightened 1,2,3,4 but about a turn or less at a time. My torque wrench was set at 25fp and the nuts are brass with the thick (Belleville??) washers. When the wrench had clicked at 25 across all 4, I waited a couple minutes and went across them again. All 4 tightened a bit further before the wrench clicked again. I stopped after the third pass. I assumed that this was gasket crush.

I too would like to know if sequence matters, especially when the manifold set was machined flat.

LOL! What woke me up in the night was that I suddenly remembered that I had applied aluminum anti-seize to the studs. In the back of the red Les Andrews book there is a chart regarding torque values. If anti-seize is applied, it says to reduce your setting 45%! So is my torque now sitting at the equivalent of 36.25? Well, in a few minutes of night terror, I was certain that I had stripped all four brass nuts and probably the studs in the block too....

I think the gasket is pretty thick and is compensating for any reasonable go-slow sequence.
 
alexiskai said:
Yeah, but the 45 ft-lb torque is being applied to the nuts on the studs, not to the studs in the block. And the nuts are brass, not Grade 8 steel. And there are concave washers under the nuts. It's not analogous.
Click to expand...


And the cylinder head doesn't reach several hundred degrees either.
 
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