Torque plates

I know y’all in the US regularly talk about the importance of using torque plates when boring Norton barrels.

But over here, it’s not so common at all.

I’m considering making some.

Can y’all please share pics of what you’ve got / used?

And some advice on how to mount, what torque to use, etc?

Thanks in advance.

I used torque plates extensively building auto engines. We when used them we tightened them to the same setting as the spec for the heads. FWIW, we also heated the block to get it closer to the conditions it actually faced while operating. A bore that is perfectly round when cold might not be when heated depending on how it expands. Since engine block castings are (or were) not perfect, we also tried to find engine blocks that had thicker bore walls on the thrust side of the bore. They maintained "roundness," and therefore a better ring/wall seal when hot. Castings can have more or less thickness on any side of the bore just based on good or bad luck!

I have no experience with this on a Norton, though the same issues/concerns should be involved. Heck, at worst they certainly can't hurt and MIGHT be a big help.

MexicoMike said:

I used torque plates extensively building auto engines. We when used them we tightened them to the same setting as the spec for the heads. FWIW, we also heated the block to get it closer to the conditions it actually faced while operating. A bore that is perfectly round when cold might not be when heated depending on how it expands. Since engine block castings are (or were) not perfect, we also tried to find engine blocks that had thicker bore walls on the thrust side of the bore. They maintained "roundness," and therefore a better ring/wall seal when hot. Castings can have more or less thickness on any side of the bore just based on good or bad luck!

I have no experience with this on a Norton, though the same issues/concerns should be involved. Heck, at worst they certainly can't hurt and MIGHT be a big help.

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Question: Did you ever verify that they helped not only at the top of the bore but nearer the bottom?

I'm just guessing that to be effective for our vintage bikes they would need to be one at the top and bottom.

You might want to have a look at Patrick Seager's page and see how it does it. Maybe ping him and ask. Pretty
detailed oriented type he is.

Here's a photo of Ken Canaga's torque plates.

Torque plates made a notable difference sometimes and no difference other times re the difference in roundness at the top/bottom of bore. It's really all about the individual engine. For example, on one occasion we found a big block engine made 60 additional HP with no changes other than a rebuild with torque plates/honing. All other engine parts remained the same. On another engine we found that there was no difference at all. It's all about individual engines. But, as stated, at WORST, it can't hurt.

How about taking a freshly bored/honed barrell, measure it with a dial bore gage, then bolt on a head, re-check. Also, bolt to a set of cases and see if thst affects it. Fairly quick & simple. Report back.

I don't think torque plates make enough of a difference with iron barrels, but with aluminium types they probably do.

Martyn.

I experimented a lot with using sleeved cast iron cylinders for 920 engines back in the '70s and '80s. I found that torque plates made a large difference in performance for them. I've detailed those results here somewhere on the forum, but it's been a few years. In summary, without using the torque plates, you get major blow-by at the top of the bore at the spots where the through bolt counterbores are bored through to fit the sleeves. You will see large black spots in those locations. The engine will also smoke noticeably. It will still feel like it makes a lot more low end and mid-range power, but not so much on the top end. Using torque plates to bore and hone fixes those problems. I also found that I needed to cut grooves for copper o-rings in the top of the liner to keep from getting leakage past the (copper) head gasket.

I never saw the need for them with stock 750 and 850 cylinders. I went through several of them in road race bikes, without using torque plates, and never saw any bore problems. When I built an 850 out to 79.5 mm bore for my grandson's Commando a few years ago, I used the torque plates. Not sure if it was really necessary, but the cylinder does get a bit thin at that bore, and it wasn't that much extra work, so I did it just in case.

I also didn't use them with 750 and 850 alloy cylinders in the race bikes, and had no bore issues. If I were doing a new 920 conversion to an alloy cylinder, I would probably use them, just in case. The only one of those I've done recently was a 81 mm bore Maney cylinder on an ultra-short stroke 750 for landspeed racing, but it didn't have the problem counterbores (bolt heads on top of cylinders instead), so I didn't use them for it either.

Just relating my own experience, for whatever it's worth.

Ken

I made a torque plate years ago and found it made only the tiniest difference. I only used it once and abandoned the project. The carefully drilled and bored hunk of iron now makes a good doorstop.

Before I’d invest in materials and time to make a torque plate, I would verify experimentally that such a device is needed. As others have suggested, measure the subject cylinder with a bore gauge and mark it so you know exactly where and by how much it is out of round. Then add a load to the cylinder bolt holes, at the specified torque, via 1) cylinder head attachment or 2) other rigid non-deforming large slugs of metal at each bolt hole. Measure the loaded cylinder with the bore gauge and see how much it distorted. If it hasn’t distorted at all, there is no point in having a torque plate involved in the process, since boring it at room temperature with or without a torque plate will yield the same hole. If the cylinder does distort, you’ll have to assess the magnitude of distortion you are comfortable with and act accordingly.

You could also perform the testing at both room temp and elevated temp to note any differences in concentricity as a function of temp, but since you are boring at RT, there likely isn’t much you can really do about a difference in the elevated temp result.

seattle##gs said:

I made a torque plate years ago and found it made only the tiniest difference. I only used it once and abandoned the project. The carefully drilled and bored hunk of iron now makes a good doorstop.

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Maybe rename it a "talk" plate?

So boring and 850 motor out to 920cc is good if it works without oil passing the piston rings ? Bragging rights must be important. I think some people kid themselves when they modify motors. The question is always 'what is more important'. If you do all the performance mods, they must add up to create the fastest motor ? I am fairly certain that a Commando with Amal carbs on petrol will never be fast. That new Royal Enfield 750 twin has fuel injection. You will have to bore your engines out much bigger, to catch them.

acotrel said:

So boring and 850 motor out to 920cc is good if it works without oil passing the piston rings ? Bragging rights must be important. I think some people kid themselves when they modify motors. The question is always 'what is more important'. If you do all the performance mods, they must add up to create the fastest motor ? I am fairly certain that a Commando with Amal carbs on petrol will never be fast. That new Royal Enfield 750 twin has fuel injection. You will have to bore your engines out much bigger, to catch them.

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Al,
The Enfield is a 650 actually.
And if you think a decent modified Commando can’t beat one of those, then you’ve obviously never ridden one … or the other …

Sorry ! I apologise. I know you should never knock somebody else's go. I race my 500cc short stroke engined Triton in Allpower C grade for many years. My main rival had the same bike, It had the same motor but 650cc, . Mine had a close 4 speed box, his had the standard box. We both used methanol. I many races I could get up beside him, but I could never beat him. Om one occasion I lowered the overall gearing, softened the suspension, and lowered my tyre pressures. I led an Allpowers race for almost a complete lap. I was passed by a Kawasaki 900 and two Kawasaki 750 towards the end of the longest straight. Then I ran off while trying to miss the guys in front of me. With a smaller capacity motor, you always have gearing problems. My bike desperately needed 6 gears close ratio. If I geared it high, it was slow at the start of the straights, gear it high and it was slow towards the ends of the straights. With my Seeley 850, I now have 6 speeds close ratio.
It is not the size of what you have, but how you use it.

Fast Eddie said:

Al,
The Enfield is a 650 actually.
And if you think a decent modified Commando can’t beat one of those, then you’ve obviously never ridden one … or the other …

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You are lucky it is a 650, you might have had a real problem.
I cannot imagine a motorcycle which is made in India beating a UK made motorcycle of the same type, which is the real deal. But they might give you some curry.

I think you had better get up to date on Enfield in India. The make a lot of Interceptors. They sell them all. A modern bike with traditional styling . A bike that runs well and doesn't break. It cannot be long before they punch it out and hot it up a bit. If they don't aftermarket boys will.

Passed one on the M25 today.... Not my cup of tea (was offered one at a good price some time back) but nice to see someone out there mixing it up

Onder said:

I think you had better get up to date on Enfield in India. The make a lot of Interceptors. They sell them all. A modern bike with traditional styling . A bike that runs well and doesn't break. It cannot be long before they punch it out and hot it up a bit. If they don't aftermarket boys will.

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Funny things. Way back when the Triumph Trident was first to average 100mph in the Isle of Mann TT. Today, the 200mph bikes average 130MPH. A 0CC bike recently average 121.9mph. All those CCs aren't going to matter much soon . True that the electric superbikes go less laps but 10 years ago there was no such thing. Now there are electric jets.

Then there the electric Honda that is self-balancing and will follow you like a puppy.