Oil leak at the head gasket

lcrken · Sep 8, 2016

comnoz said:
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I talked to an engineer at ARP a little while back. He said any cutting or polishing on the shank of a high tensile bolt should be done lengthwise -just like polishing a con rod.

I don't know how much of a problem cutting around the bolt would create, but if I were going to be selling them I would follow that rule.

We may have to look into some waisted barrel bolts but they would probably be in 180,000 psi black oxide since they don't show and the price would be much more reasonable. I am sure it would cut down on barrel distortion and the tendency to pull the case threads which does happen on racebikes from time to time. [ie, Kenny's bike at Willow a couple years ago -with the kit bolts]. Jim

I'm looking at using stainless through bolts because they do show in the Maney cylinders, and that's what I'm working with at the moment. Also, as you sort of mentioned, the bolts Maney supplies with them are not the stock items with the extended threads, so look like good candidates for waisted fasteners.

I'm still looking at whether I can do something in the lathe with the toolpost grinder similar to how you do them in the mill. Not sure yet if that will work, but I'll find out.

I'm not planning to sell any of this stuff, just doing it for the fun of it. If I have to have some made to get what I want, I'll have some extras to sell to any interested forum members, but that's about it.

Ken

comnoz · Sep 8, 2016

lcrken said:
I'm looking at using stainless through bolts because they do show in the Maney cylinders, and that's what I'm working with at the moment. Also, as you sort of mentioned, the bolts Maney supplies with them are not the stock items with the extended threads, so look like good candidates for waisted fasteners.

I'm still looking at whether I can do something in the lathe with the toolpost grinder similar to how you do them in the mill. Not sure yet if that will work, but I'll find out.

I'm not planning to sell any of this stuff, just doing it for the fun of it. If I have to have some made to get what I want, I'll have some extras to sell to any interested forum members, but that's about it.

Ken

Yeah, I forgot- they do show in the Maney barrel.

I have used regular ARP stainless reduced hex head bolts in the past. All that is required is reducing the diameter of the built in washer to fit down in the counterbore. 12pt bolts would work also

I could waist cut some of them with my setup if you don't come up with a way to do them. Jim

MS850 · Sep 13, 2016

Im using cNw waisted head blots and belleville washer, I just did a head retorque with about 60mi since replacing the head gasket, fiber type. I marked the bolts position and loosened and torqued, the bolt returned to the same spot that I marked.

robs ss · Dec 20, 2016

I've read this thread with interest as it probably pertains to my 650SS.
A measure that I couldn't see addressed here is whether the full 30ft/lb torque is still recommended to be given to the 62 thou waisted bolts
My calculations, for a 3/8", 26tpi bolt, torqued to 30ft/lb gives 21kN tension, resulting in around 300MPa stress and, for the 650SS grip of 45mm, 0.0027" extension of the bolt.
Now, that stress is getting up there, not proof for high tensile, but high.
If the bolt is waisted by 0.062", the extension is the same but the stress goes up to 430MPa - 40% higher.

Using an operating temperature of 400F (205C) the differential expansion between the cylinder head and bolt over the grip length of 45mm is approx. 0.0042", which is probably high enough to cause failure, over time, of the original bolt. It doesn't, most probably because the aluminium head creeps at high temperatures, reducing the 0.0042" extension to some lower value, also resulting in the annoying symptom of losing torque on the bolts.

My concern here is with the desirable increase in "springiness" of the waisted bolts will come a reduced ability to cause the bolt-life-saving head creep. this will mean a substantial increase in the 430MPa torque induced stress to some substantially higher value - potentially resulting in fatigue failure of the waisted bolts over time. These bolts are not torqued to a proof value so will be subject to stress cycles - stress cycles mean fatigue at this level.

I'm not wishing to be a wet blanket and maybe my assumptions and calculations are faulty. Matt cNw and Jim C, have these numbers been checked to ensure the waisted bolts are durable?

Cheers
Rob

robs ss · Dec 20, 2016

By the way - when I searched for belleville washers, that might eliminate the need for waisting the bolt I came across Key Bellevilles (PA USA).
They have a part number K-0750-C-076 which has an OD of 0.75", ID of 0.38", thickness of 0.07" and a dish of 0.03" with a flat load of 4822lb (~21KN). It looks as though two of these could provide the required load at half deflection combined with 300% more than the needed 0.004" movement during hot-cold cycles.
The penalty would appear to be 0.065" less thread engagement in the barrel (existing 0.090" flat washer compared with 0.155" (2 x 0.070" thickness plus half 0.030" dish) for the two bellevilles.
I'm not convinced 1.5mm less engagement in the iron barrel is significant. (anyone had one of these pull out?)
Any thoughts on this?
Cheers
Rob

worntorn · Dec 20, 2016

lcrken said:
I'm looking at using stainless through bolts because they do show in the Maney cylinders, and that's what I'm working with at the moment. Also, as you sort of mentioned, the bolts Maney supplies with them are not the stock items with the extended threads, so look like good candidates for waisted fasteners.

Ken

The use of stainless bolts changes things quite a bit, mostly for the better. Stainless in general has a much higher coefficient of thermal expansion than carbon steel does, so it comes closer to keeping up with the aluminium.
Stainless is also in general much more ductile than carbon steel and has a greater elasticity, making it a springier spring, which is what the waisting of the carbon bolts also does.

Glen

comnoz · Dec 20, 2016

robs ss said:
I've read this thread with interest as it probably pertains to my 650SS.
A measure that I couldn't see addressed here is whether the full 30ft/lb torque is still recommended to be given to the 62 thou waisted bolts
My calculations, for a 3/8", 26tpi bolt, torqued to 30ft/lb gives 21kN tension, resulting in around 300MPa stress and, for the 650SS grip of 45mm, 0.0027" extension of the bolt.
Now, that stress is getting up there, not proof for high tensile, but high.
If the bolt is waisted by 0.062", the extension is the same but the stress goes up to 430MPa - 40% higher.

Using an operating temperature of 400F (205C) the differential expansion between the cylinder head and bolt over the grip length of 45mm is approx. 0.0042", which is probably high enough to cause failure, over time, of the original bolt. It doesn't, most probably because the aluminium head creeps at high temperatures, reducing the 0.0042" extension to some lower value, also resulting in the annoying symptom of losing torque on the bolts.

My concern here is with the desirable increase in "springiness" of the waisted bolts will come a reduced ability to cause the bolt-life-saving head creep. this will mean a substantial increase in the 430MPa torque induced stress to some substantially higher value - potentially resulting in fatigue failure of the waisted bolts over time. These bolts are not torqued to a proof value so will be subject to stress cycles - stress cycles mean fatigue at this level.

I'm not wishing to be a wet blanket and maybe my assumptions and calculations are faulty. Matt cNw and Jim C, have these numbers been checked to ensure the waisted bolts are durable?

Cheers
Rob

They have been checked and tested.

Do not forget that with a standard, non-undercut bolt, the stress must be figured at the thinnest part of the bolt -which is the base diameter of the threads. So in other words the stress figure does not change nearly that much -it is simply spread over a much longer area of the bolt which makes it less likely to fail. Jim

lynxnsu · Dec 24, 2016

worntorn said:
lcrken said:

I'm looking at using stainless through bolts because they do show in the Maney cylinders, and that's what I'm working with at the moment. Also, as you sort of mentioned, the bolts Maney supplies with them are not the stock items with the extended threads, so look like good candidates for waisted fasteners.

Ken

Click to expand...

The use of stainless bolts changes things quite a bit, mostly for the better. Stainless in general has a much higher coefficient of thermal expansion than carbon steel does, so it comes closer to keeping up with the aluminium.
Stainless is also in general much more ductile than carbon steel and has a greater elasticity, making it a springier spring, which is what the waisting of the carbon bolts also does.

Glen

just found this VERY interesting thread
about stainless being better suited , in pre 93 ducatis , the 4 long studs holdin the heads and barrells onto the cases ,broke at the base , flush with the cranckcases or a bit lower , at an allarming rate
these bolts were waisted , as are the later ones ,made in stainless
the later ones are steel , again also waisted , but those are bulletproof

so my question is why did the more elastic ones break and the less elastic steel ones not?

always thought that i was lazy because after about 10000km on the commando a slight oil weep appeared on the top fins of the barell after i stopped retorquing , happy to know now why

lynxnsu · Dec 24, 2016

Fast Eddie said:
lcrken said:

I was so taken with Jim's work that I decided to try reducing the shank size on some fasteners. These are a set of 850 through bolts that I turned down on the lathe, and then polished with emery cloth strips. I tried using my tool post grinder, but didn't get any better finish than with a circular carbide insert in the lathe. I may give grinding another try with some new wheels. these are 5" bolts that still have to be cut down to length for the Norton. I'm saving them for an iron barrel engine, where they don't show. For the Maney cylinders, where the bolts are exposed, I'm planning to pick up some stainless bolts from ARP, and see if I can do a similar modification to them. I'm also planning to do a set of stainless head bolts, starting with ARP bolts. I'd use CNW bolts, but they aren't the right thread for the Maney cylinders.

same for me, eddie ,send you pm

Click to expand...

lcrken · Dec 24, 2016

Update on the waisted stainless fasteners front. I gave up on finding a good method to waist the bolts on my machinery, and sent several sets of ARP stainless fasteners to Jim (comnoz) to be waisted. For the cylinder bolts, I did have to shorten the ARP stock lengths to the standard Commando size, as well as one set to lengths to suit a shorter cylinder for the 75 mm stroke 750. I'll post some pictures when I get them back.

Ken

Oil leak at the head gasket

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