Valve spring break in procedure

Now here's a new one on me, which about all engine areas are, so BFD eh.

http://www.compcams.com/Pages/415/truth ... rings.aspx


Breaking In a Spring

1. It is important for new springs to take a heat-set. Never abuse or run the engine at high rpm when the springs are new. Upon initial start-up, limit rpm to 1500 to 2000 until the temperature has reached operating levels. Shut off the engine and allow the springs to cool to room temperature. This usually will eliminate early breakage and prolong spring life. After the spring has been “broken-in”, it is common for it to lose a slight amount of pressure. Once this initial pressure loss occurs, the spring pressure should remain constant unless the engine is abused and the spring becomes overstressed. Then the springs must either be replaced or shimmed to the correct pressure.

Adding my very limited bit,
I have a local spring maker on the door step, Springs are very complex items[according the them,the makers} once the spring is formed,it is heated to remove any stress
This Normalizing heat removes the iregular grain the wire got through compression and tension during bending. If the spring is a "Good design" the memory will be retained ,providing it is not subjected to excessive heat, Load is at its greatest with the misuse of valve spring compressor, springs are often compressed until they become coil bound.

Springs are complex and some my teachers loved to tease us with calculating resonance in multi spring systems, ugh. I really got in to spring construction when sourcing progressive fork springs a decade ago and would still like to try titanium ones. The cryo tempering shops have a good sales pitch on doing it to springs, which Peel had done and maybe saved her head gear etc, on the '04 over rev event. Recent bantering on rocker oiling and spring temps had me searching references to find this one.

I don't know what we/me could/should do any differently on initial run ins to break in a new spring set. I basically warm up for 5-ish minutes over 2000 rpm, then shut down to check and diddle and cool off and retorque, then run it 10-15 min, blipping up over 2000-3500 rpm then ready to switch oil, re-torque and hit the road and really put some heat to it. Its usually been rather cold on my initial run ins so usually don't bother with a fan and w/o load don't burn much fuel to over heat in that short span. On first road return is when I'd check valve lash but don't think the spring set has any affects on that though.

hobot said:

Now here's a new one on me, which about all engine areas are, so BFD eh.

http://www.compcams.com/Pages/415/truth ... rings.aspx


Breaking In a Spring

1. It is important for new springs to take a heat-set. Never abuse or run the engine at high rpm when the springs are new. Upon initial start-up, limit rpm to 1500 to 2000 until the temperature has reached operating levels. Shut off the engine and allow the springs to cool to room temperature. This usually will eliminate early breakage and prolong spring life. After the spring has been “broken-in”, it is common for it to lose a slight amount of pressure. Once this initial pressure loss occurs, the spring pressure should remain constant unless the engine is abused and the spring becomes overstressed. Then the springs must either be replaced or shimmed to the correct pressure.

Click to expand...

Hard to see how you are going to aceceive that when you have a Honda 250/297 six when it will not tick over and has to be revved to 8,000 revs on starting because of the full race camshaft :!: :shock:

Good point, small fourstroke racers :!: i would guess the Norton factory. plus all the others did nothing special to ensure the springs where broken in, or anything else, my prewar single as open hair pin,no problem with them over heating...it's the oil spray i worry about :!:
If my memory serves me...the detemper is approx 350c ..do nortons get that hot inside the rocker box?

john robert bould said:

If my memory serves me...the detemper is approx 350c ..do nortons get that hot inside the rocker box?

Click to expand...

Of course not, not even close.

Oh My an over cammed Honda need 8000 to keep breathing enough, whew. Guess it takes tougher spring alloy and tempering than our clunkers that begin to come apart at 8000 or at least become cartoon-ish elastic distorting.

I've only found 2 references online so far, 1st one said valve significantly weakened by 475' F [posted in the rocker oil thread] and below coating sites that says 400' F. That is entirely possible to reach in Norton heads, especially one at WOT on best power fuel ratio. I assume the coating shop is being conservative to sell coatings. I have to keep reminding myself that spring temps is more from their own internal friction and surface rubbing than combustion heat conducted into them, at least that's what all the valve spring info sites state. So possible to have cool head reading but over heated springs. How would we/me even know before, a instant of tinkling then kaboom.

http://www.techlinecoatings.com/article ... rticle.htm
Says SS valves good to 900' F.

hobot said:

I've only found 2 references online so far, 1st one said valve significantly weakened by 475' F [posted in the rocker oil thread] and below coating sites that says 400' F.

Click to expand...

475 F is no where near john robert bould's 350 C (which works out to about 662 F)

Judging by the lack of evidence of even small to moderate volumes of broken valve springs due to heat in our beloved Norton twins over the years I suspect heat on the springs is a non issue. I think you are more likely to have premature valve spring failures due to mishandling and damaging them during installation (nicking the shotpeened surfaces and other surface protective treatments).

It would be interesting to take an indirect temp reading on the springs; I would be surprised if they were any hotter than 300 - 350 F

I've not privy to the scope of seasoned Nortoneers but never heard of any Norton valve spring heat failures either. Still searching and still finding the 475' F threshold starting to degrade tempering.


Excessive Heat
1. 475 F. can be considered as the maximum temperature for aircraft engine valve springs. Consider that cylinder head maximum is typically 500 degrees F. and this temperature is taken between the cold (intake) and hot (exhaust) portion of the cylinder. At 500 F for CHT it is conceivable that the exhaust valve spring could be at or above this temperature. Above 475 a couple of changes start to occur in the valve spring. Fatigue life is reduced as the shot peened compressive residual stress is relieved. Temper strength is reduced above 475 degrees.

From experience over-heated valve springs are often dark and crispy from oxidized oil. They also have collapsed meaning that their free length is reduced.
http://mechanicsupport.blogspot.com/201 ... anics.html

Heres some valve wire data spec's. It says heat stress relieving and nitriding done between 4-500' C, not F.
http://www.suzuki-garphyttan.com/net.ns ... 0SC_En.pdf

http://www.amspringwire.com/valvetechbulletin.pdf

All a bit academic for a Norton twin.

Read through the following: http://www.nortonclub.com/docs/OilTemp.pdf

I am thinking that Norton valve springs at 475 F, well you have bigger fish to fry somewhere else, like the stressed aluminum around the cylinder head on a Norton.

At 475 F you are well beyond the flash point of most motor oils. I never saw a hint of this on the Nortons I worked on.

I could see this happening on maybe the older Norton twin cast iron heads or the old HD Sportster heads but aluminum saps the heat away too quick

Insulating washers are a springs best friend...

R Model Tony said:

Insulating washers are a springs best friend...

Click to expand...

+1

My current race builds have a steel spring seats which shoulder on the valve guides (right or wrong) and pretty much insulate the springs from the aluminum (aluminium) head; that and a supply of oil keep the springs cool.

All more or less moot.

Dances with Shrapnel said:

R Model Tony said:

Insulating washers are a springs best friend...

Click to expand...

+1

My current race builds have a steel spring seats which shoulder on the valve guides (right or wrong) and pretty much insulate the springs from the aluminum (aluminium) head; that and a supply of oil keep the springs cool.

All more or less moot.

Click to expand...

John, I have an old Ron Wood/Axtell short stroke 750 head that had the spring seats like that. Here are a couple pictures that show how the guides were made to include a shoulder for the spring seats. I always assumed the idea was to thermally insulate the springs from the head, but never thought to ask Axe about it. The two heads I had Axe do for me back in the '70s had a more conventional spring seat arrangement. Is this similar to how you've been doing it? I'm rebuilding the head, and making new oversize guides in the process, and I'm debating whether to make them like the originals, or to go back to the conventional Norton spring seat layout. I'd appreciate hearing your thoughts on the subject.





Ken

Ken,

Not sure if I can give you much first hand insight to the use of these types of guides. This is what Herb Becker has set the engines up with and that is what I plan to stick with. Jim Comstock did not seem too fond of these when he cut the seats; maybe he can chime in a bit on his concerns.

Below is a series of photos showing the 500 cc ultra short stroke (Commando) head with the new Beryllium Copper guides, the old guides and the valve spring seat. As you can see from the guide length, this motor was built to race and rebuild, not so much for durability.

The first two pictures below show the new Copper Beryllum guides installed on the intake and exhaust sides. This head has seen some battles with a few catastrophic engine failures so it is race weary.



The picture below shows the old guide (Aluminum Bronze or AMPCO45?) with a steel shim pack in place

The following picture shows the valve spring assembly with special steel seat which nests onto the top of the guide shoulder. The springs are from some sort of Honda sports/race car; I cannot remember the details but they yield a high seat pressure.

The following is a close up of the valve spring seat.

The final picture shows how the old guide nested into the special seat.


I like this arrangement since it keeps the valve guides from backing out of the head; the guides have nowhere to go. Furthermore, oil and air can easily circulate beneath the spring assembly, presumably for better cooling of the springs; my guess is that this happens and it is good.

I can also see my way through being able to leave (or place) a thicker bridge of material at the bottom of the spring pocket where it gets close to the roof of the port on the intake side.

A down side to this may be having less spring pack travel.

Again, these are all my hunches and guesses. Herb set my two Nortons up like this and I plan to continue on with it this way although I may be a little more generous with guide lengths in future builds..

Since it's so close to the topic, I'll ask the question here.
Has anyone had experience with the JS beehive setup.

Thanks for sharing the info, John. Those are indeed short guides, but for an engine that is gone through regularly, I wouldn't think they would cause problems, other than maybe more frequent replacement. I had wondered if part of the reason for using this arrangement was to keep the guide from moving around. In the Ron Wood head one of the guides was removable with finger pressure when I got it, and the others were fairly easy to push out with a drift. Definitely no significant interference fit there. There is not a lot of support left around the intake guides after porting, so they loosen up pretty rapidly. You probably have a similar situation in your heads. I think I'll go ahead with just duplicating the existing guides in aluminum bronze with an oversize O.D., and use a steel spring seat. I got the head from Ron without any of the valve train, so I can use whatever I choose for springs and valves and such. I think I'll probably go ahead with the beehive springs. I've got to make new valves anyhow, so I can cut them for the higher collets needed for the beehives. So many projects, so little time.

Ken