torque spark plugs
Racer
Joined: Aug 2009
Posts: 289
Likes: 1
From: Tucson Arizona
"Are we going to the moon in this or what ? :
As a matter of fact, I am a rocket scientist (for those used to model rockets the bird on the pad weighs 52 pounds at launch and is powered by an Aerotech M1315 solid fuel motor. That motor is equivalent to about 640 Estes "C" motors).
1) Torque is a moment, a force applied at a distance. Therefore the correct notation is lb-ft (although mathematics suggest that ft-lb is equivalent). "lb/ft" or "ft/lb" are incorrect as they imply a type of linearly distributed load (pounds per foot) or nonsense (foot per pound).
2) The presence of lubrication is important when determining a torque value. For a given torque, forces are increased from a lubricated fastener. Effectively, you are overtorquing. May not be a moon shot, but you'll regret stripped threads and broken fasteners.
3) And I agree with the above comments about putting them in and snugging them up. Except for my Nissan truck, I never had a vehicle with sufficient clearance to use a torque wrench.
Steve
As a matter of fact, I am a rocket scientist (for those used to model rockets the bird on the pad weighs 52 pounds at launch and is powered by an Aerotech M1315 solid fuel motor. That motor is equivalent to about 640 Estes "C" motors).
1) Torque is a moment, a force applied at a distance. Therefore the correct notation is lb-ft (although mathematics suggest that ft-lb is equivalent). "lb/ft" or "ft/lb" are incorrect as they imply a type of linearly distributed load (pounds per foot) or nonsense (foot per pound).
2) The presence of lubrication is important when determining a torque value. For a given torque, forces are increased from a lubricated fastener. Effectively, you are overtorquing. May not be a moon shot, but you'll regret stripped threads and broken fasteners.
3) And I agree with the above comments about putting them in and snugging them up. Except for my Nissan truck, I never had a vehicle with sufficient clearance to use a torque wrench.
Steve
Last edited by azrocketman; Mar 8, 2010 at 10:23 AM.
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
"Are we going to the moon in this or what ? :
As a matter of fact, I am a rocket scientist (for those used to model rockets the bird on the pad weighs 52 pounds at launch and is powered by an Aerotech M1315 solid fuel motor. That motor is equivalent to about 640 Estes "C" motors).
1) Torque is a moment, a force applied at a distance. Therefore the correct notation is lb-ft (although mathematics suggest that ft-lb is equivalent). "lb/ft" or "ft/lb" are incorrect as they imply a type of linearly distributed load (pounds per foot) or nonsense (foot per pound).
2) The presence of lubrication is important when determining a torque value. For a given torque, forces are increased from a lubricated fastener. Effectively, you are overtorquing. May not be a moon shot, but you'll regret stripped threads and broken fasteners.
3) And I agree with the above comments about putting them in and snugging them up. Except for my Nissan truck, I never had a vehicle with sufficient clearance to use a torque wrench.
Steve
As a matter of fact, I am a rocket scientist (for those used to model rockets the bird on the pad weighs 52 pounds at launch and is powered by an Aerotech M1315 solid fuel motor. That motor is equivalent to about 640 Estes "C" motors).
1) Torque is a moment, a force applied at a distance. Therefore the correct notation is lb-ft (although mathematics suggest that ft-lb is equivalent). "lb/ft" or "ft/lb" are incorrect as they imply a type of linearly distributed load (pounds per foot) or nonsense (foot per pound).
2) The presence of lubrication is important when determining a torque value. For a given torque, forces are increased from a lubricated fastener. Effectively, you are overtorquing. May not be a moon shot, but you'll regret stripped threads and broken fasteners.
3) And I agree with the above comments about putting them in and snugging them up. Except for my Nissan truck, I never had a vehicle with sufficient clearance to use a torque wrench.
Steve
Racer
Joined: Aug 2009
Posts: 289
Likes: 1
From: Tucson Arizona
Steve
Melting Slicks
Joined: Feb 2010
Posts: 2,077
Likes: 72
From: Reno Nv
Several sources I checked indicate that specified torques should be reduced 25% to 50% for lubricated fasteners. If I remember correctly, the aluminum head plugs have crush washers. I'd torque by feel instead of a wrench (I have not put plugs in the Vette yet but I've done it many times on my Corvairs).
Steve
Steve
Yea, a lot of older aluminum heads (like bike motors) used the crush washers.
The tapered seats on todays heads make the torque a bit less important, they seal and hold very well.
I'm almost religious on using a torque wrench on the racecars but I never torque plugs. Snug them and give them a 1/16th turn, never had a problem.
Last edited by Bill32; Mar 8, 2010 at 06:50 PM.
Pro
Joined: Oct 2009
Posts: 679
Likes: 0
From: vero beach florida
Yep, I use 30% on antisieze. There's different reductions for different lubes. In the ARP book, they even have different values for ARP thread oil vs motor oil ( rod bolts).
Yea, a lot of older aluminum heads (like bike motors) used the crush washers.
The tapered seats on todays heads make the torque a bit less important, they seal and hold very well.
I'm almost religious on using a torque wrench on the racecars but I never torque plugs. Snug them and give them a 1/16th turn, never had a problem.
Yea, a lot of older aluminum heads (like bike motors) used the crush washers.
The tapered seats on todays heads make the torque a bit less important, they seal and hold very well.
I'm almost religious on using a torque wrench on the racecars but I never torque plugs. Snug them and give them a 1/16th turn, never had a problem.
But yes, I snug them and give them a little extra.
Melting Slicks
Joined: Feb 2010
Posts: 2,077
Likes: 72
From: Reno Nv
The bottom line is that "a little extra" on a plug after it's snug is just fine. 1/32. 1/16, 1/8th turn if the wrench will do it. Unless you're completely hamfisted and just have to overtighten everything, the way you described it will work everytime. So will the undefineable 1/16.
Overtightening's another story.
The cars I play with have the plugs pulled and reinstalled 40+ times a year. I've never had a loose plug or one that was stuck.
I do use a torque wrench everywhere else.
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 765
torque on threaded fasteners is a science in itself. there is literally hundreds of books written on the subject. NO FLAMES HERE, but granted, you can get away without using one, but it doesn't mean its the correct or proper way to do a job. anyone, especially with aluminum heads should use a torque wrench on the plugs! 
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
The 96 Vette FSM says 15 Lb Ft - Page 6-11 Notice the absence of punctuation.
The 86 Vette FSM says 22 lb. ft. Notice the capitalization and punctuaton ('period - .' ) differences - Page 6A1-29 with no distinction between iron or aluminum heads mentioned.
Choose your poison.
Jake
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Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
You'd probably hear the sound of compression leakage. May not begin right away, but over time it'll increase.
This is not a really critical torque spec just as long as torque spec isn't greatly off. In fact, many guys who have screwed on engines for years use muscle memory in torquing the spark plugs.
If I was to prepare a listing of the most critical torque specs, with the most critical ones at the top and the least critical at the bottom, spark plug torque would be down near the bottom.
Jake
This is not a really critical torque spec just as long as torque spec isn't greatly off. In fact, many guys who have screwed on engines for years use muscle memory in torquing the spark plugs.
If I was to prepare a listing of the most critical torque specs, with the most critical ones at the top and the least critical at the bottom, spark plug torque would be down near the bottom.
Jake
Racer
Joined: Aug 2009
Posts: 289
Likes: 1
From: Tucson Arizona
10.5 feet tall, 7.5 inches diameter, 52 pounds at launch, M1315 power, dual redundant electronics for recovery initiation, max altitude approximately 6000 feet.
Phenolic impregnated tubing for body, birch plywood fins, fiberglass nosecone
Used for National Association of Rocketry (NAR) Level 3 high power certification
Picture taken at Rainbow Valley near Phoenix, AZ.
Steve
Phenolic impregnated tubing for body, birch plywood fins, fiberglass nosecone
Used for National Association of Rocketry (NAR) Level 3 high power certification
Picture taken at Rainbow Valley near Phoenix, AZ.
Steve
