Posted by ian_sutherland at December 08. 2011
Previously wrote:
Using torque plates makes sense for the cylinder block, especially aluminium alloy as I've learnt from the problems experienced with this block, and torqueing the bolts with a hot engine makes sense too, but wont the damage, i.e distortion due to expansion coeeficients between different materials, have already been done if the initial torque settings are with the engine only warm? You would also have to remove the hot head to gain access to the cylinder through bolts, which in my opinion are the cause of the problem. Also I suspect oil/combustion leaks may be a problem until the engine reaches operating temperature. I'm not a fan of RTV especially were oil ways are present.
Thanks for the advice Ian, what are your experiences with alloy cylinder blocks on Commandos, road or race?, Have you experienced problems with leaks or distortion?
Cheers Simon.
Hi Simon,
Sorry, if I was not very clear or miss-understood, is your block already distorted, if so it's leaking or smoking, and you will have already removed it, and you can probably see the uneven wear pattern.
This has been an ongoing problem with bike engines, especially since more and more parts, started being made of different alloys, looking for more power.
I remember it really becoming a problem with high perf Harley engines in the early 80's, and I think/remember that's where using torque plates really started and/or took off. I certainly cannot remember much discussion on the issue before that. I/we had a dunstall barrel about the same time period and they were quite notorious, for twisting and leaking.
I used the word "warm" because I do not want to be sued, because someone really keen somewhere, scald's themselves with boiling oil.
If you stick a good quality Iron/steel sleeve into aluminium it's going to shift, especially if it has not been thru a few heat cycles. Add in not loaded in the way it is going to be ,and it's going to be more of a problem. A reason why a properly made all aluminium nikasil block with good rings is a much better solution, all be it a bit more expensive. The correct grade of aluminium sleeve must also be used, or the plating departs.
Here is what I am going to do with my own brand new aluminium cylinder for my own latest 850. I am not assuming someone loved it like me.
I am going to take my 850 alloy barrell and make sure that the cases base to cly surface is flat and square to one another and then, that it is to the crank. Now check the head surfaces to one another they are flat and square .
I am now taking my 1 inch thk aluminium torque plates, and I am bolting it all together, using some high temp grease on the presure surfaces, and some light grease or light oil on bolt threads, personally now I use torque lube because I have some. Torque it up as per sequence, if the specs are dry that you use, add 2ft lbs if now lubing. Taking this assembly I stick it in the oven, and then outside to cool, From around 200-220deg F , anymore and you can change heat treat of aluminium parts permanatly. repeat 2-3 times, I use the 3 times lucky rule. Check it hot and when cooled after removing torque plates,for round, If the surfaces are still flat and square, you are ready for honing. Put it all back together, warm it up again, and warm your oil. depends on how you are doing it and with what. I have a lise 4 stone set hone and a bobilie ball hone for finishing, if you are dipping it in fluid that's different to a flowing a source of lube, and you have the boiling point of the fluid to consider to, you don't want more than you have, to have flashing off and killing you softly, We are trying to replicate running conditions, for the final honing, as best we can.
Now your mating surfaces should be still square, and flat, but your bore may seem a little off when cold and not torqued but good when torqued & hot. We are looking for within tolerance, at it's best when simulating conditions. We are never going to truly achieve this because of moving parts and changing pressures, within the cylinders.
I am assumming your barrel is off right now, and if you don't have access to torque plates, bolt it up with the bare head and cases and try it in the oven a couple of times to make sure it is not moving anymore. Remember about the temp limits so as not to damage your parts.
I do not use base gaskets, unless I am shimming for head clearance purposes, shouldn't apply to you, then I use solids for the thickness I want. I Use REAL Rolls Royce, Hylomar blue, they have a new race one now as well, it seems a bit thinner, but stands slightly higher heat, make sure of oilways, it's not like other sealants Thats for the base. On the cylinder head I use solid copper, or other metal types, on high perf. Norton or norvil best quality steel flame ring gaskets are fine on stock engines. I coat them all with copper slip, sparingly it goes a long way. Torque it all down in sequence, now run it ride it a short distance, put some loads thru it. break the nuts, bolts, studs or hex bolts whatever you are using just enough to release the tension in them, in reverse order of torquing sequence and retorque them, I do them hot if I am using copper/metal gaskets, and if I have played with the head in anyway, cold is fine for regular gskt and purposes. done correctly it is not going to get any better. You are starting off from cold with no stress in the motor, cases and cylinder are relativly thin mat'l next to that lump, I don't worry about the internal bolts, it's all aluminium now and when hot, the lower rate bolts should only add a compressive load. If your really worried about that do them up with everything naked and check with a bore gauge. Even warm it up and check. I don't see it.
With your distored barrels, they have moved in accordance with the internal stresses placed upon them, and within them. I cannot tell you what they will do next, only that bolting them up and putting them thru some heat cycles will do that, how many have they already been thru. Then correct them once they have settled. square them to the cases/crank, then head to that. Now warm up the bores and simulate the loaded barrels to the cases, and distortion caused by that giant chunk called a head.
I once shaved 1/2 inch off a set of 500 barrels rewelded the center drilled and tapped it, and used this method to tighten it, it does not have a full face, it's 10.5:1 and it does not leak, and is 750 quick, I've built racers, but not much lately due to gimphood. This is the way I do my bikes and my buddies bikes. I am building my ideal 850 at the moment, all out of bits, I"ve considered removing the steel liner and getting an aluminium one to press in, then sending it off once it's settled, for coating, but at the moment I'm sticking with the steel , to spend my dosh on other parts. It's never going to be perfect somewhere, as your running hot I hope, and gently when cold, I know what I prefer. The bike doesn't know it's racing.
I Hope that gets it, I've pressed in a good few sleeves and they move around untill they settle. I don't know who made yours, but ? are they cast in sleeves like old jap bikes, or cast barrels, then bored and the sleeves pressed in, If so did they leave them in the press for a while after pressing, did they use a pressing oil, have they already cycled them. There are so many different ways you can do things, that affects them for stress relieving , before we go re-stressing them.
The way I look at it, once the only thing made of steel that's stationary, is the sleeve, your problems should be fewer, true different grades of aluminium can expand at different rates, but once you have run it and retorqued it, it shouldn"t move again. You retorque the head to allow the parts to re-align themselves from the running stresses placed upon them. I don't feel that's a concern with the case to barrels joint. If your worrying about bolts putting loads thru the aluminium, I think not, all cylinders would fail and you should be able to trouble shoot it.
What makes you think they are distorting, I recently had a problem with a buddie's BSA, the cylinders were bored out of alignment, with the crank.
Sorry this is a novel, hope it help's
Regards Ian
