Heat Insulator Under Valve Springs

I didn't mention that I already installed them in the first post.
I double checked the spring movement at full lift. Even with the insulators I still have plenty of spring left. I was reading the Archives in the tech section. It suggested that if there is room install them. So I am taking the bike to AMA Vintage days on Friday with the insulators. Thanks for the input.

KZ

I have a '74 Commando. When I took the head (RH4) apart, there were no heat insulators under the springs. The parts manual indicates 4 required except for the RH1 head. The service manual says only use insulators on pre 1972 engines.

Does anyone know if the insulators should be installed under the inlet valve springs? :?:

My 74 850 only used them on the exaust side....not on the inlet.

I've reconned a couple of 850 heads recently and both had insulators under each valve spring. Definetly they have to be under the exhausts, but I would always fit them as a precaution to the inlets as well. And they are cheap to buy so worth doing it.

Mick

I don't think you can just install the heat insulating washers on the intakes if they weren't there before because wouldn't they possibly make the spring coil bound at maximum lift? I'm not familiar with the 850s but on my '72 750 they are on the exhaust only. I remember having to thin the spring cups slightly and radiusing the edges (recommended for early combat) because it is pretty close.

you definitly have to put those isolation on your exhaust valve-springs
this is how I put my springs in
-measure your lift (of your camshaft off course
-measure your valvespring lenght istalled in your head
-take your spring out and measure howmuch kilos this gives(with a press and scale)
-compress your spring by the lift x 1.1(rockerarm ratio);This should be at least 90kg (max for me is 110kg)

-now compress your spring further and you should have at least 2mm to go before coilbound !!!!!!!!!

you can fiddle with shimms to give the desired preload but check last step(coilbound)
all this is not relevant if you are not going to risk your investment and keep her under 4000rpm
But the fun is a bit higher-up the revscale

lynxnsu said:

you definitly have to put those isolation on your exhaust valve-springs

Click to expand...

Can anyone explain why to me....?

The alluminium will melt and the oil will coke inside the head before the spring gets deteriorated
by heat....!

Apart from spring height settings what useful purpose does the heat insulating shim actually do?

Mike

conkers said:

lynxnsu said:

you definitly have to put those isolation on your exhaust valve-springs

Click to expand...

Can anyone explain why to me....?

The alluminium will melt and the oil will coke inside the head before the spring gets deteriorated
by heat....!

Apart from spring height settings what useful purpose does the heat insulating shim actually do?

Mike

Click to expand...

The spring will start showing damage from heat as low as 400 degrees F. You definitely need the washers there. Jim

Does the oil not bathe the springs and circulate?

Oil flashpoint is what.. 150 celcius (300°F) and my guess runs cooler than that...

I was suprised to find them on my head as I have never seen them on any of the hundreds of heads I have rebuilt, admittedly this is my first Norton and I am intruiged by these (phenolic resin?) heat insulators and their purpose.

Obviously they are there for a reason and I will replace them and run them, but I would love to know more about the history of useage and why they came to be used.

Mike

Yes the springs are cooled by the oil, but the area of the cylinder head right above the exhaust port easily reaches 450 degrees and more. That is why they are needed on the exhaust side.

That is also what cooks the oil in a Norton motor but since there is such a small amount of the total oil passing through the head it doesn't contribute much to the overall temperature of the oil in the tank.

Some heads used them on the intake side also. If they were there then they need to be re-installed to maintain the correct valve spring installed height.
Norton twins have used them as far back as I know. Jim

Interesting theory.

You say 450 degrees, farenheit I assume.

I saw no signs of oil coking in my head, so I am still unconvinced of the necessity of the insulators.

Interesting article on thermal barrier coatings..

http://www.circletrack.com/enginetech/c ... ewall.html

For arguments sake lets say that valve springs running at 400°F lose pressure... I still can't see how a spring in  a circulating oil bath at 300°F could get so hot.

Heat would pass from the aircooled head's exhaust port and combustion chamber to the spring seat  (around 200°F?) and through the valve stems which are much much hotter I would imagine?)

If the stem of the valve is signigicantly hotter than the headcasting (even in close proximity to the ex port)
then passing its heat throung the top retainer to the spring and to the oil.... is it feasible that
insulating the bottom spring retainer from the head will concentrate the heat in the spring and may even increase the spring temperature?

Mike

The heat path through the spring seat to the spring is much shorter than up the valve stem. Plus the alloy used in a valve stem is a poor conductor of heat.

I have a thermocouple buried deep in the head between the two chambers on my daily rider. I have a readout on my dash. It is not very close to the exhaust port and yet I see 400 degrees regularly running at speed down the highway so I can see why they want to isolate the spring from the head in that area. Jim

Last year I rebuilt my 750 motor, a 1971 vintage engine. I used three service manuals , a factory Norton manual a Clymer manual and a engine rebuild manual in video form from Mick Hemmings. In each of these reference items the insulators were referred to as needing to be installed in the intake and exhaust valve spring locations. When I initially dismantled the seized engine ,that had been in a barn I believe for a very long time, it had these insulators in both locations. I believe that at somr point I read that these insulators are there to prolong the life of the springs.

This is why the springs on all other engine fail at such an early stage,

The hotest part of head ain't deep between the chambers its toward the out sides near front, about where the exht valves and springs live. There is no such thing as "oil bath" in rocker boxes unless the drain blocked, its just a bit of spittle sprayed out of spindle seams and rocker end. Alan Goldwater directly measured oil temps inside the exht rocker boxes. Norton did a pretty neat job of placing the hottest parts farthest apart and most exposed to the wind. I always thought the deep center would be but that ain't what the thermo images reveal.

Temperature and Lubrication of the Norton Motorcycle Engine
http://www.nortonclub.com/docs/OilTemp.pdf

Hobot,
Terrific article on oils and testing. Kinda makes me wonder about that diesel oil I have been running! Good thing I don't live where it hits 90 degrees very often.

Better save that article for the next "what oil is best" thread.

Russ

If the parts book shows them USE THEM.

It's so easy to look at the parts book diagrams and lists on Old Britt's website, in the appropriate year and section, that there is no reason NOT to.

Brilliant article and lots of good points...

So Red Line 20/50 it will be then... although here in sweden it's not very often we get such warm weather, but it does happen on occasion!

I will run with the heat insulators, I was just trying to find out why they fitted them and now I know.

I friend of mine (a real life professor and the only one I know) who works in the aerospace industry is a bike nut and has done a lot of work with ceramic coatings, he has developed and tested ceramic coated piston crowns and combustion chamber (including valves) on his Aprillia, and it is holding up after two seasons.
He suggested a theory with regard to the thermal insulators on the Norton that they would not only stop heat transfer to the spring, to minimise the risk of spring tension loss, but also to reduce the amount of heat the spring would pass into the oil. (Thats not word for word because he used a lot of big words!)

We discussed ceramic coating of valve springs and he has offered to coat some spring retainers and/or the tops and bottom of the springs so I can do some temperature/spring pressure comparisons. I have a bunch of porsche 968 springs laying around that I can use for testing and comparison, if I get round to it I will test them cold and hot (400F) to see how much pressure they lose and compare this to the thermal insulators and ceramic coated spring seat faces.

No promises, but I have some time on my hands and access to the testing equipment. If I get round to it I will share my findings.

Thanks for all your input guys, this has been a fascinating discussion.

You are awesome.

Mike.

I got to read Alan posts when he hung out on NOC and BI lists. I have his pdf text and image of coolest '70's space age oil cooler ever, designed by Alan, billet fins built in a band under the logo of oil tank side cover. I need to send it to someone digi savy to be able to post to forum delight and inspiration.

Still there just ain't much oil flow in head and Harley found more oil in flow head didn't do much but make the oil in tank too hot so even extra coolers couldn't keep up. IIRC oil is worth about 6 % of our engine cooling. I was going to open more oil flow to exhaust side in Peel but now see its not a good idea so will spray water if CHT at plugs gets over 400'F. One reason for the insulators might be to stifle oil coking on springs. Hi end race cars oil spray springs though or would fail soon. Maybe some extra oil flow, if it would drain out fast enough via the little space in lifters.

Springs action internal friction and rub/spin/impact on end washers also creates a lot of heat. Impressive if the ceramic can last for seasons let alone a couple of years there. Double springs tend to rub on each other adding heat too. But really and truly extra special materials and treatments is over kill except for racers pressing rpm endurance limits, not more mundane public Commandos. On the other hand can't be too rich or too talented so why not put in cryogenic tempered bee hive springs ceramic coated as icing on the cake.

The fit of the springs has a lot to do with the temperature that the springs see as well. A tight spring will run hotter but have better valve control from more "coulomb" (friction) damping. Too little and you run cooler but can loose some control over the valve. There are many nuances in the spring in the basic design and fit and how it can help control the valve.

Click to expand...

To determine peak temperatures, indicator paints, e.g.: http://www.tempil.com/ are very useful and inexpensive.

Coating article sale pitch says 400'F in steel springs is bad juju.
http://www.techlinecoatings.com/article ... rticle.htm