Heat washers and valve springs

Status
Not open for further replies.
pommie john

pommie john

Joined
Nov 18, 2005
Messages
922
Country flag
I've got my head back from a guy who's fitted new guides ( after the previous people who worked on the head did some serious damage). He found evidence of valve float and his assessment was that the standard springs had a closed seat pressure of 75lbs. Not enough for a PW3 cam. He couldn't shim them enough without them going coil bound at full lift.

So, he's fitted a set of Kibblewhite lightweight springs and retainers. However, to get a reasonable ( 95lb ) seat pressure he had to fit them without the heat washers under them. The washers shimmed the springs too much he says.

He reckons that loads of engines run without heat washers and there will be no problem.

What do the experts think?
 
Would those 'loads of engines' all be watercooled ?

Going to be interesting to see how this pans out...
 
From memory I believe springs can be tempered at temperature as low as 130 degrees centigrade. You need to check that figure with a metallurgist. I would have thought there would be enough oil in the head to carry the heat away from the springs.
 
john robert bould said:
Will the heat from the valve simply travel up and heat the collet cap..then travel down onto the spring?
Click to expand...


The spring lower cup sits right on top of the exhaust port which is very hot. That, I assume is the heat path.
 
Can you refit the original spec heat washers to effectively detuned the spring pressure? This is my concern with the kW light weight setup.
 
Dkt26 said:
Can you refit the original spec heat washers to effectively detuned the spring pressure? This is my concern with the kW light weight setup.
Click to expand...


Do you mean fit the Norton lower cup with the heat washer instead of the KW lower cup?

I'll measure thicknesses and report back.

edit: No. The KW lower is thinner than the Norton one.
 
Info I have is that you should aim to use the heat washers 'if you can' but you should make your decision based on getting the correct set up with your cam etc.

So far I have installed them exhaust only.
 
pommie john said:
Dkt26 said:
Can you refit the original spec heat washers to effectively detuned the spring pressure? This is my concern with the kW light weight setup.
Click to expand...


Do you mean fit the Norton lower cup with the heat washer instead of the KW lower cup?

I'll measure thicknesses and report back.

edit: No. The KW lower is thinner than the Norton one.
Click to expand...

Dang
 
Hmm.
I've just had a look at the KW website.

On the instructions for the OEM replacement kit, they say the fibre washer must be used to obtain the correct installed height, but on the racing kit, they don't mention it.

Maybe they're supposed to run without?
 
Fast Eddie said:
The JS beehive spring kits do not use the insulating washer.
Click to expand...

Not entirely true....Jim's words are:

'Install the original non-metallic washers below the bottom washers and check for .050” coil bind clearance when using a pry bar and dial indicator. Use shims to adjust and balance if necessary. High lift cams with over .4” lobe lift (not valve lift) may or may not have room for the original non-metallic washers.'

So he seems to think it is more important to get the spring height correct, meaning achieving the minimum 0.050" coil bind clearance. And clearly he is saying try with them in first, before you decide to leave them out.

I found room to fit them on the exhaust, but not on the inlet, I am using only the spring seat and metal shims there.
 
I've run my road race engines without the insulating washers for years with no problems. I've done that with S&W, KPM, and RD springs. When I started racing my PR it had stock springs, with insulating washers on the exhaust only. I used standard valve spring shims to get the spring heights right with the aftermarket springs.

Ken
 
Mick Hemmings told me that on reassembly of my big valve head with PW3 cam motor if I couldn't get the 50 thu. clearance then don't refit the washer. He also states this in his engine rebuild dvd. If there is inadequate clearance to prevent the spring going coil bound this will damage things (maybe many things to) far far quicker than any heat issues that may arise over time and will only effect the spring. Mick says in the many years he has been doing this heat issues because of not refitting the insulating washer have never caused a problem.
 
SteveA said:
Fast Eddie said:
The JS beehive spring kits do not use the insulating washer.
Click to expand...

Not entirely true....Jim's words are:

'Install the original non-metallic washers below the bottom washers and check for .050” coil bind clearance when using a pry bar and dial indicator. Use shims to adjust and balance if necessary. High lift cams with over .4” lobe lift (not valve lift) may or may not have room for the original non-metallic washers.'

So he seems to think it is more important to get the spring height correct, meaning achieving the minimum 0.050" coil bind clearance. And clearly he is saying try with them in first, before you decide to leave them out.

I found room to fit them on the exhaust, but not on the inlet, I am using only the spring seat and metal shims there.
Click to expand...

Yes, and they do come with shims and data to adjust as needed. I do not recall where I may have used the fiber washers, but I do remember the detail of getting the height just right.
 
I emailed KW last night, and this morning they have replied ( very efficient of them) to say "We would not recommend leaving the insulating washers out".

Back to square one.

I'm most tempted to go with Ken's advice. Since this is a road bike it'll never get as hot as one on the racetrack so maybe it won't be a problem. It's the only way to get the correct installed height.
 
lcrken said:
I've run my road race engines without the insulating washers for years with no problems. I've done that with S&W, KPM, and RD springs. When I started racing my PR it had stock springs, with insulating washers on the exhaust only. I used standard valve spring shims to get the spring heights right with the aftermarket springs.

Ken
Click to expand...

Hi Ken
Would you mind saying when you started running your PR, what was the cam? 2S, 3s, or 4S or an aftermarket?
In the early 90's, I was pit crew for a few norton guys and it was not uncommon to run a stock combat. One of my friends spent many many thousands to only get up to 54-56 RWHP. Though I'm sure there was a loss of broad torque. So in conclusion the lack of the intake washer was no big deal on the track.
Move forward a few years....around 2000?
MY combat, on a ride home from a nearby city...broke the oil pump . :x

Well the autopsy showed the intake inner spring had brittled and started to disintegrate into bits and chunks and made their way to the oil pump which locked it up and KABLAM. oil pressure guage goes to ZERO.
It went home in the back of my pick up.
So for me I will watch the springs much closer and don't expect combat springs to last as long as stock cam springs. I'd expect to change them well before 25.000 miles next time.
 
Status
Not open for further replies.
Back
Top