Torque? Alloy Dunstall barrell?

Hi, im posting this on behalf of my pal Hal, Hal Record up currently in Palmer Alaska. not far from that chick,, "I can see Russians from my kitchen window", so,, my pal Hal is up in the great white north and fettling a bevy of vintage bikes, Triumphs, BSA's and some Nortons.
His newest issue is he has some sort of Alloy big bore cylinder, im easily confused but I *think* he said it was a Dunstall 800 cylinder? Its alloy, has steel or iron liner sleeves and im unclear on this part,, he has steel inserts for the threads?

I do know this for sure,, some of them are 22TPI which is rather coarse, he bought a tap and cleaned the threads,, but as I warned him, there is well known issues with inserts and threads as well as liner issues on those cylinders. Ive heard this for years. I told him many people install Timeserts or other proven inserts for the threads,, but ive heard many tales of woe keeping those alloy cyls on the road or track.

So i was hoping some people who have run alloy cylinders on Nortons,.... specifically Nortons,, if you could share your experiences, torque recomendations, and any other hints or tricks on these. I personally have never run alloy cylinders on a Norton so can only give general feedback.

While im not looking to get this discussion sideways,, theres an interesting ongoing discussion in Sportster and Buell circles on Alloy cylinders, the Evo Sporty motors benefit for many reasons running a alloy cylinder and many have proven reliable, But many well respected tuners and builders prefer on a hot rod street bike to run after market Cast iron cylinders as they, once they heat cycle a few times,, are far more stable.


So,, I know a few of you guys have run alloy cylinders on a Norton, can you share please? Hal will be watching here, he pokes his head in from time to time but isnt a registered member. He doesnt have the patience to do much on the net except read emails and shop ebay. please be gentle, a lot of older guys are like that

Hi, I remenber Ludwig when he had received a Norvil alloy cylinder who replaced the helicoil with his own copper-alloy inserts ...nice if he see that post!

The two biggest problems with the Dunstall 810 cylinders are

1. Made in a soft alloy, so threads strip, and nuts sink into alloy and loosen

2. Thin liner, which is prone to break and drop bottom section down into crankcase.

That doesn't mean you can't make them work for a while. Thread inserts and regular tightening of fasteners are essential. I built one for a friend's race bike, and it lasted a fair number of races before the liner broke and trashed the bottom end.

The modern alloy cylinders from Steve Maney, Robertson, et. al. are cast in much stronger alloy, and the liners are thicker, so they work much better. Lots of them used in street and race bikes with no problems.

Ken

It might be possible to harden the alloy by ageing the barrels in a 100 degree C oven for a couple of weeks. I would replace the liners with something very strong such as a cast iron which has nickel in it.

Hi, what's about "nickasil" in those alloy cylinders ? and regarding inserts what your advise timeserts or homemade (as seen in the forum with some ally copper vaves guides)??

acotrel said:

It might be possible to harden the alloy by ageing the barrels in a 100 degree C oven for a couple of weeks. I would replace the liners with something very strong such as a cast iron which has nickel in it.

Click to expand...

As I recall (but can't be positive) Dunstall cylinders were cast in LM5, which isn't a heat-treatable alloy. I think most of the modern alloy Norton cylinders are cast in LM25, which is heat treatable, and can go to much higher tensile strengths and hardness numbers than LM5.

Ken

If the barrels are castings, the aluminium is probably high in silicon to get flow. It would probably still age harden.

acotrel said:

If the barrels are castings, the aluminium is probably high in silicon to get flow. It would probably still age harden.

Click to expand...

Actually, that's one of the problems with LM5, it's a fairly low silicon content alloy, 0.3% max. LM25, which is similar to the A356 that is commonly use in the US, has something like 6.5 - 7.5% silicon. In the fully hardened condition, it has almost twice the tensile strength and hardness of LM5.

Ken

I am running the Manley alloy barrels in an 850 engine. When the engine was first built and running I thought I had made a terrible mistake. Could not get the head gasket to seal, and was terrified I was going to strip the threads out of the barrel on the retorque procedure. Eventually it worked out. Look up the thread on annealing and sealing copper head gaskets.
The casting is a bit rough, some of casting needs to ground off for the nuts to fit.

norsa1 said:

I am running the Manley alloy barrels in an 850 engine. When the engine was first built and running I thought I had made a terrible mistake. Could not get the head gasket to seal, and was terrified I was going to strip the threads out of the barrel on the retorque procedure. Eventually it worked out. Look up the thread on annealing and sealing copper head gaskets.
The casting is a bit rough, some of casting needs to ground off for the nuts to fit.

Click to expand...

I believe Steve casts his cylinders in LM25, and they are way superior to Dunstall cylinders in all respects. Just out of curiosity, which nuts did you have trouble with?

Ken

With the Manley barrels I had trouble with the two front short studs coming down from the head. The two nuts are very small for a head bolt, nonetheless I had to trim away some metal to get a wrench on them. On the stock arrangement they are the elongated nuts at the front. The Manley barrels require a completely different securement method. After the re torque procedure everything stayed tight this season.

Thanks, Norsa1. I had the same problem with the alloy cylinders from Drew Robertson that I used to sell. The solution was to use a 12-point nut that took a smaller box end wrench size. I couldn't get the larger wrench for the hex nuts to fit without some grinding.

Ken