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Hi Paul,
What starting torque & what angle would you use on BJ8 Healey head bolts?
D
What starting torque & what angle would you use on BJ8 Healey head bolts?
D
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Torque Wrenches
- Thread starter J Eade
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Paul Johnson
Jedi Warrior
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Jeff correctly noted that it would be silly to use a damaged stud. I think he's working in a hobby race shop, but when you transfer mindset to a commercial, high volume situation it looks a little different. As well, think of a head that uses bolts rather than stud/nuts. A little thread damage down low, or some debris or worse, fluid down at the bottom is what I had in mind. I believe the aircraft industry uses the angle method quite a bit, and auto manufacturers began to do so a decade or so ago.
Dave asked about specific values for a Healey. Afraid I don't know. Have never looked for a cross reference, but that might be a good project. If it bears any fruit I'll post it here.
Dave asked about specific values for a Healey. Afraid I don't know. Have never looked for a cross reference, but that might be a good project. If it bears any fruit I'll post it here.
Paul, my comment about using a damaged stud was not intended to be a snide remark, but a legitimate question.
No, I don't work in a hobby race shop, unless building the cars that I race for a hobby qualifies. I'm a former Engineering Development Technician for GM, an aircraft mechanic for the past 38 years, and currently work as a prototype machinist.
I guess my point on the damaged stud was that we have members of widely disparate skill levels here, and I didn't want someone with minimal skills to think that it would be acceptable to re-use a damaged fastener. "When in doubt, throw it out." I tend to be a stickler for proper shop practices.
When I started working on aircraft, the angle method was used sparingly, but has become more prevalent. I was just reviewing a factory engine assembly manual for the new Corvette, and the angle torque method is specified for only fasteners in critical areas, such as head bolts, bearing caps, rod bolts, crank balancer, etc. Interestingly, the head bolts are to be replaced after each use.
As far as the Healy head bolt question, it could be calculated, but the clamping force required, the mechanical characteristics of the bolt, etc. would need to be known.
Hope I didn't come across as a total flaming idiot.
Jeff
No, I don't work in a hobby race shop, unless building the cars that I race for a hobby qualifies. I'm a former Engineering Development Technician for GM, an aircraft mechanic for the past 38 years, and currently work as a prototype machinist.
I guess my point on the damaged stud was that we have members of widely disparate skill levels here, and I didn't want someone with minimal skills to think that it would be acceptable to re-use a damaged fastener. "When in doubt, throw it out." I tend to be a stickler for proper shop practices.
When I started working on aircraft, the angle method was used sparingly, but has become more prevalent. I was just reviewing a factory engine assembly manual for the new Corvette, and the angle torque method is specified for only fasteners in critical areas, such as head bolts, bearing caps, rod bolts, crank balancer, etc. Interestingly, the head bolts are to be replaced after each use.
As far as the Healy head bolt question, it could be calculated, but the clamping force required, the mechanical characteristics of the bolt, etc. would need to be known.
Hope I didn't come across as a total flaming idiot.
Jeff
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I guess that my point is that presently, torque angle tightening only applies to a few specialized automotive & aircraft applications where the stretch vs angle has been carefully calculated & measured. Bolt stretch measuring also applies to a "few" applications where both ends of the fastener are accessable. Torque to yield fasteners are also in this specialized category. To get accurate tightening, most new bolts should be tight - loose cycled about five times before final tightening. For the majority of "old British cars", careful use of a torque wrench, even with it's shortcomings, is still the most practical way to get correct fastener tightening.
As an experiment, I tried measuring head stud height change above the head as an indication of stretch & torque. The amount of stretch is proportional to the bolt length & different length bolts actually require different stretch measurments. On my particular head bolts, 75 ft lb corresponds to .0095" stretch. Whole lot of bother & probably not necessary on the "average" engine.
An aside: Many years ago I installed head bolts on an engine with some blind head bolt holes. There was coolant in some of the holes & the hydraulic lock actually blew a chunk out of the side of the tapped hole in the block.
D
As an experiment, I tried measuring head stud height change above the head as an indication of stretch & torque. The amount of stretch is proportional to the bolt length & different length bolts actually require different stretch measurments. On my particular head bolts, 75 ft lb corresponds to .0095" stretch. Whole lot of bother & probably not necessary on the "average" engine.
An aside: Many years ago I installed head bolts on an engine with some blind head bolt holes. There was coolant in some of the holes & the hydraulic lock actually blew a chunk out of the side of the tapped hole in the block.
D
Paul Johnson
Jedi Warrior
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[ QUOTE ]
Hope I didn't come across as a total flaming idiot.
Jeff
[/ QUOTE ]
Not at all, Jeff. I always read your posts as from a well trained person, well thought through, and as a good double check on screwy things I might say.
Hope I didn't come across as a total flaming idiot.
Jeff
[/ QUOTE ]
Not at all, Jeff. I always read your posts as from a well trained person, well thought through, and as a good double check on screwy things I might say.
Bob Buxbaum
Jedi Hopeful
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My turn, guys.
1) It is only fair to tell you that I am a Snap-On dealer.
2) I can NOT sell outside of my "territory", and won't. It's a violation of my franchise agreement (and I agree with it).
3) I know a little bit about torque "wrenches".
Torque "wrenches" aren't. They are (or should be) precision instruments. That said, if any of you are involved enough with your cars to actually need a torque tool, it's worth having a good one.
A little background is needed. It was mentioned earlier by Dave Russell that torque tools are not accurate above or below 20% of scale. In most cases this IS true. The higher the quality of the tool, the greater portion of the working range is useable. Also, it is better NOT to buy one with a real wide working range. In other words, a 3/8" unit that goes from 5-75 lbs/ft will usually be more accurate than one that goes from 10-100. Next, very few companies are making most of the available torque tools. Central, Precision, CDI, and Snap-On are about the only readily available domestic units. Snap-On is the ONLY one that includes a calibration statement with the unit. It makes for interesting reading to see just how accurate S.O. torque tools really are. How about under 4% at full scale on any of the currently available units! Also, Snap On has three regional service centers that can repair and/or calibrate their own units, and that service is available through any Snap-On dealer for a flat fee, depending on the model.
Realistically, any decent torque "wrench" is okay on race day for checking wheel lug torque. Building an engine, rear end, or transmission is another issue. Plus or minus 10 lbs/ft on a lug nut isn't all that important, but it sure as heck is when you are snugging up a crank or head!
Just like with tires, shocks, oil, etc., buy the good stuff, and worry less about the results.
1) It is only fair to tell you that I am a Snap-On dealer.
2) I can NOT sell outside of my "territory", and won't. It's a violation of my franchise agreement (and I agree with it).
3) I know a little bit about torque "wrenches".
Torque "wrenches" aren't. They are (or should be) precision instruments. That said, if any of you are involved enough with your cars to actually need a torque tool, it's worth having a good one.
A little background is needed. It was mentioned earlier by Dave Russell that torque tools are not accurate above or below 20% of scale. In most cases this IS true. The higher the quality of the tool, the greater portion of the working range is useable. Also, it is better NOT to buy one with a real wide working range. In other words, a 3/8" unit that goes from 5-75 lbs/ft will usually be more accurate than one that goes from 10-100. Next, very few companies are making most of the available torque tools. Central, Precision, CDI, and Snap-On are about the only readily available domestic units. Snap-On is the ONLY one that includes a calibration statement with the unit. It makes for interesting reading to see just how accurate S.O. torque tools really are. How about under 4% at full scale on any of the currently available units! Also, Snap On has three regional service centers that can repair and/or calibrate their own units, and that service is available through any Snap-On dealer for a flat fee, depending on the model.
Realistically, any decent torque "wrench" is okay on race day for checking wheel lug torque. Building an engine, rear end, or transmission is another issue. Plus or minus 10 lbs/ft on a lug nut isn't all that important, but it sure as heck is when you are snugging up a crank or head!
Just like with tires, shocks, oil, etc., buy the good stuff, and worry less about the results.
[ QUOTE ]
[ QUOTE ]
torque wrench? what's a torque wrench? seriously...does anyone ever use those things?
[/ QUOTE ]
I'll make a note not to buy any cars you may ever have for sale. /ubbthreads/images/graemlins/grin.gif
Bruce
[/ QUOTE ]
You'd be lucky to get any of the cars I have for sale. They all run well and have been taken care of. I suppose you torque your spark plugs too? It just seems a little obsessive to me....I can almost always tell when something is tight enough or not. Up to this point, I've never had a problem occur that's associated with not using a torque wrench. I DO have one..its just that I've not found a need to use it. /ubbthreads/images/graemlins/eek.gif
[ QUOTE ]
torque wrench? what's a torque wrench? seriously...does anyone ever use those things?
[/ QUOTE ]
I'll make a note not to buy any cars you may ever have for sale. /ubbthreads/images/graemlins/grin.gif
Bruce
[/ QUOTE ]
You'd be lucky to get any of the cars I have for sale. They all run well and have been taken care of. I suppose you torque your spark plugs too? It just seems a little obsessive to me....I can almost always tell when something is tight enough or not. Up to this point, I've never had a problem occur that's associated with not using a torque wrench. I DO have one..its just that I've not found a need to use it. /ubbthreads/images/graemlins/eek.gif
[ QUOTE ]
Hey Steve, I actually DO torque my spark plugs. Overtightening a plug can not only snap it off, it may change the gap.
And as far as <u>ALMOST</u> ALWAYS being able to tell if something is tight or not, I can too. But when I use the torque wrench, I can ALWAYS tell.
Jeff
[/ QUOTE ]
I'm willing to bet that most people don't use them, including mechanics at dealerships.
Hey Steve, I actually DO torque my spark plugs. Overtightening a plug can not only snap it off, it may change the gap.
And as far as <u>ALMOST</u> ALWAYS being able to tell if something is tight or not, I can too. But when I use the torque wrench, I can ALWAYS tell.
Jeff
[/ QUOTE ]
I'm willing to bet that most people don't use them, including mechanics at dealerships.
Jim Weatherford
Jedi Trainee
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Does that mean I should take my Sears "clicker" back and get a beam model?
Jim Weatherford
Jedi Trainee
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Steven; If you think I mis-quoted my saying: "Lord of Darkness", then you’ve not owned a '56 Bentley S1 or a Jensen Healey!!! The electrics on at least these cars in my experience are 100% satanic in nature. /ubbthreads/images/graemlins/devilgrin.gif
Jim Weatherford
Jedi Trainee
Offline
Guys, I'm serious when I wrote..."Does that mean I should take my Sears "clicker" back and get a beam model?" I'd really like to know your opinions.
Jim, I wouldn't take it back, but read my comments regarding calibration.
For critical engine assembly torques, I use a dial indicator type, which is essentially a beam style, that has a dial indicator rather than the beam pointer. The resolution is much more accurate, and it has an adjustable tattle-tale pointer you can either pre-set at the desired torque value, or allow to sweep with the indicator needle to record the highest torque applied.
In my opinion, both types of wrench have their place in the tool box. If you do a lot of differential work, or fine work requiring low torques, I'd recommend a dial type inch pound wrench. Handy when setting pinion pre-loads, for instance.
Jeff
For critical engine assembly torques, I use a dial indicator type, which is essentially a beam style, that has a dial indicator rather than the beam pointer. The resolution is much more accurate, and it has an adjustable tattle-tale pointer you can either pre-set at the desired torque value, or allow to sweep with the indicator needle to record the highest torque applied.
In my opinion, both types of wrench have their place in the tool box. If you do a lot of differential work, or fine work requiring low torques, I'd recommend a dial type inch pound wrench. Handy when setting pinion pre-loads, for instance.
Jeff