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In late shovel service manual it tells you to use torque plates on cylinders when boring and honing. Is it necessary? And if it is what about early years or pan heads cylinders?
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I'd say...not a bad idea...safer is better, BUT....
zillions of successful bore/hones have been done without torque plates. -
Rick!
If you measure distortion from fastener stress from torque plates, you will find it to be less than the piston clearance on a 74" cylinder until you get into the .060" oversize range. Then it becomes very significant: The skirts will rub the cylinder spigots if a simple poke'n'hope borejob is performed. It's round when honed un-stressed, but goes squirrely when torqued to the cases.
This is the basis for all the barnyard horror stories for larger overbores supposedly requireing greater clearances, running hot by nature, and fragged cylinders. Honing them pre-stressed eliminates the problem.
80" chubbles were little more than 74" cylinders overbored to .060" to begin with, thus plates are essential, particularly on the base.
Distortion from the headbolts pulls the borewalls outward, so there is little danger other than losing ringseal and horsepower. The spigots, however, spring both inward and outward, sometimes as much as a .006" differential. With stock clearances, it is easy to see why friction and fragging would result.
So use them if you want to achieve an ideal on any overbore.
Even for stock bore cylinders if sleeved.
....CottenComment
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Thank you for your reply.What would you recomend on .050 o/s bore using n.o.s pistons? How much interference would you use for piston to cylinder wall and should I use torque plates?Comment
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Rick!
As I posted: use them if you want to achieve an ideal on any overbore.
And Factory spec for clearance of course.
"Interference" is what we wish to avoid.
Please remember that proper use of stressplates includes installation at the same torque as they were fitted at.
You will need an adapter or two for your torsion torquewrench.
.....CottenComment
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Cotten! Can you tell me where I can buy torque plates for pan heads and torque wrench adaptors?Comment
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Off-hand, no.
All the commercial plates that I remember back into the '80s were all one-size-fitz-none, although were several sources.
The idea of a stressplate is to replicate installation as exactly as possible, and catalog offerings always seemed bad compromises.
Pro shops usually have made their own for each motor configuration.
That's why 'zillions' have been poked-n-hoped without them for generations.
Same thing for adapters when it comes to installation and re-torque within the chassis, although common Snap-on extensions will work on the bench.
Please remember that any adapter must make a right angle from the wrench to the fastener, or it will change the actual torque applied.
The simplest tooling is to find a common
cheapo imported torsion wrench (plenty accurate enough!) that has it's 1/2"square drives pointing both up and down. (Critical for retorques in the chassis.)
Then get a common "obstruction" wrench, the "C"-shaped variety, that has 5/8" on one end, and 9/16" on the other.
The third component is a 5/8" allen socket.
The 9/16" end will fit on most 1/2" square drives giving you two ways to use it to get onto hard to reach base nuts. The other drive on the torsion wrench gives you two more. This means four different arrangement possibilities to get at them.
The 5/8" allen socket allows the obstruction wrench to be reversed to attack the headbolts.
Attached is a photo of many various adapters (mostly for Chiefs), but the top is the arrangement I have described.
Don't even consider a silly "clicker" torquewrench. Bury it instead in the back yard somewhere.
....CottenComment
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Cotten,
Thank you!
RickComment
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