Torque plate twist
Torque plate twist
(OP)
Just a question.
I was wondering if an aluminum torque plate should be used if you are going to use aluminum heads - I know they don't but should they?
It seems that if the torque plate is to simulate the distortion of the block when the head is properly torqued down so that the cylinder is as true as possible during operation, you should use a material that is going to simulate that distortion as closely as possible. You do not have to go to an metalurgical expert to know that aluminum has different properties - tensile strength, elastic limits, fracture limits, yeild strengths, compressive strength, hardness, thermal properties, etc. It just seems that you may over distort the block with a more rigid steel torque plate. Some may say that the difference is nominal but some used to say the same thing about using a plate while honeing years ago. Granted you will still be duplicating any distortion of the block at the bolting points internally.
Just for instance. It the plate distorts the block .0001 over the entire deck length, is it possible that the aluminum being less rigid and softer would only distort it .00005 because the aluminum abosorbed the rest? with this theoritical situation you will hone it with twice the distortion and when you put your aluminum heads on you have over compensated.
To go even further, should you use a head gasket of the same material with the torque plate?
Or am I just over thinking?
Hmmm....
I was wondering if an aluminum torque plate should be used if you are going to use aluminum heads - I know they don't but should they?
It seems that if the torque plate is to simulate the distortion of the block when the head is properly torqued down so that the cylinder is as true as possible during operation, you should use a material that is going to simulate that distortion as closely as possible. You do not have to go to an metalurgical expert to know that aluminum has different properties - tensile strength, elastic limits, fracture limits, yeild strengths, compressive strength, hardness, thermal properties, etc. It just seems that you may over distort the block with a more rigid steel torque plate. Some may say that the difference is nominal but some used to say the same thing about using a plate while honeing years ago. Granted you will still be duplicating any distortion of the block at the bolting points internally.
Just for instance. It the plate distorts the block .0001 over the entire deck length, is it possible that the aluminum being less rigid and softer would only distort it .00005 because the aluminum abosorbed the rest? with this theoritical situation you will hone it with twice the distortion and when you put your aluminum heads on you have over compensated.
To go even further, should you use a head gasket of the same material with the torque plate?
Or am I just over thinking?
Hmmm....





RE: Torque plate twist
RE: Torque plate twist
Depends on how round you want the walls to be, and under what conditions. The torque plate design (material, thicknesses at various locations, etc) and gasket design (a gasket or simulated gasket is often used to get the load distribution closer to reality) can be critical if you want very little assembly distortion.
Some people have used FEA-derived torque plate designs to allow "honing out" of some amount of (assembly+thermal) distortion.
RE: Torque plate twist
ivymike's suggestions help, but it is a lot of trouble.
A very simple jig can reproduce the distortion created by the tension in the threads of the head bolts where the bolt holes expand into the bores. I think all other distortions are to dependant on constantly varying conditions to be of any real world value
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RE: Torque plate twist
RE: Torque plate twist
How do you simulate charge temperature effects before and after firing.
How do you simulate piston thrust against the sides of the bore.
How do you simulate crank loads on the caps and webs.
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque plate twist
Aluminum would be much lighter and easier to move around. The question of oxidizing then comes up but would it not be a factor with steel as well? Both would need to be surface trued from time to time because of corrosion. Anodized aluminum would last longer though or even a composite with steel inserts.
If that is a major concern, why not make them of stainless? Or if it is just the distortion at the bolting points, why use such a thick steel plate or even a plate at all? Just torque bolts in place with collars on them.
My original take was that the plates simulate the distortion of the block when the head is bolted on by providing a rigid point with which to cause similar core shift. That core shift distorts the cylinders either out of round or the overall center of the cylinder by a small amount (less on siamesed bores). Then the machining is done. If this is accurate, then a less rigid plate will cause less overall distortion core-wise but the same point distortion where bolting is concerned.
Does this really matter? Most likely not. It probably will not cause any measureable increase in cylinder pressure but has me curious non-the-less.
RE: Torque plate twist
Good question, but that just leads to why a plate at all? Why not just a spacer and bolt in each hole? Would it make a difference? Who really knows when it might?
I hate to mention popular opinion, but it sure is popular.
RE: Torque plate twist
RE: Torque plate twist
RE: Torque plate twist
1. The material of the plate is always the same as the head. I have never had a problem with either aluminum or steel plate oxidizing because when used, the plates are flooded with oil.
2. Thickness of the plate, well this is the thickness from the deck surface of the head to surface the stud washer or bolt flange rest on on the head.
3. The combustion chamber can be removed on the plate for honing access because the combustion chamber provides little or no structural support on the actual head. FEA shows this when analysis cylinder pressures.
4. A production style head gasket is used between the plate and the block. The gaskets are either made with an approximately .020" larger cylinder bore or, depending on tolerancing, a gasket on the high side.
5. As for running warm oil or coolant through the block and plate during honing, well what you gain from this process is usually out weighed by the cost of the process.
All of these points are for production style engines. But these same processes were and are used on high performance production engines, i.e. LS7, Viper, Ford GT, 6.1 Hemi, etc.
Just my 2 cents.
RE: Torque plate twist
I also think that race applications severely stress the components and do distort things. Anything really robust is generally considered to heavy.
speeddemon79
An opinion backed up by date and logic. Sincere thanks for your input.
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque plate twist
Call me cynical, but data supporting sales that generate huge profits always brings validity into question in my mind. Health issues and tobacco companies come to mind.
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eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque plate twist