Valve spring Installed height

[andy230]

Hello all,

Can you advise please??  Please read this for background -->

http://team-thumper.blogspot.com/2008/02/litle-more-progress-snails-pace.html

My query is about shim material.  The installed height (the height of the outer valve spring) is too high.  RD supplied shims to place under the bottom cup, to decrease this (effectively pre-loading the springs, presumably to a set load).

I got with the springs 4x shims of 0.34mm.  My installed heights are 1.5 to 2mm too great.     So this will need 4 to 6 shims per valve!

So what is the advice??  SteveH, you mentioned you had suffered this before?  I may be able to machine the bottom cups I took out to accept the new springs.  These would allow the desired installed height.  Or just use these to make shims of 1.5 or 2 mm

What are the implications of just using 1x shim per valve, and installed hight of 1-1.5mm in excess of spec??

Can I buy shim material of the required thickness??  What's your thoughts on using 6 hims under the bottom cups?!   

Cheers for now!  I saw Boyd today, some good things happened, some bad things uncovered!    More on the blog later..

a
 

[Steve H]

Andy, its quite a while ago, but I seem to remember getting new spring seats made up to suit the required installed height. I cant remember the material used, if you fit it with one of the supplied shims against the spring, then material may not be so critical.
I would stick to their recomended installation heights, if the installed height is greater then the pre-load in the spring will be less and the force keeping the rocker in contact with the cam less. This will lead to valve float, especially since the cam you are using is fairly radical.

[andy230]

Hmmmm...

Your thoughts mirror mine on valve float   

if you fit it with one of the supplied shims against the spring, then material may not be so critical.

Steve, the shims go against the head, the lower "spring cup" seats the spring (so I cant "fit it with one of the supplied shims against the spring"); the shims have to go under the cup.

I may just see if I can make flat shims of sufficient thickness out of the old bottom cups I took out and put these under the new ones...  Gotta be cheaper, quicker, easier than making new spring cups...

Ta,

a

[Steve H]

Andy, 2mm out seems a lot is it worth emailling them to ask why its so far out.

 

[guest146]

Andy not having seen your engine I am finding it a little hard to understand your problem. Are you saying the distance between your valve spring lower seat and the valve spring cap is to great?.
If this is the case I would have to think why. Did you have the seats cut out so letting the valve ride up into the head. I guess there is no reason you cant measure each valve and have shims made to the correct distance. This would be better than having several shims under each valve.

Ken

[andy230]

Hi Ken-

Are you saying the distance between your valve spring lower seat and the valve spring cap is to great?.

yes.

Did you have the seats cut out so letting the valve ride up into the head. I guess there is no reason you cant measure each valve and have shims made to the correct distance. This would be better than having several shims under each valve.

Dunno why its occured, I didn't have the seats cut...  Agreed about the single shim vs. lots of them.  Perhaps if I used RD valves rather than std I wouldn't have to shim so much...??

I think I'll maybe see if I can make new shims out of the old bottom cups and sit them under the new bottom cups...  Do you reckon it'd have to be milled?  Am trying to think "cost effective"...!


a

[guest146]

You can make a spacer/shim out of the bottom cup if its the correct thickness but its important that its true and not tilting the spring to one side and also it wont shatter if its from cast.

Ken

[andy230]

Right....

So no dremmeling it flat then... (not that I was in any way considering this, ahem...)

Ken, will this then have to be milled flat?  Can it be done on a lathe d'you reckon?

a

[guest146]

Andy

If you are concerned that it needs to be the exact distance between spring ends I would measure each one and have spacers made to fit. It would be an easy job on a lathe. That said how much diference will 1mm make to the spring pressure. Just out of intrest how much more then the original Rev limit will you be taking it to? Do these engines reach valve bounce speeds?

Ken

[Steve H]

Andy, before you start messing around, I really think you should email R+D and see what they say. 2mm  seems a long way out for it just to be a build up of tolerances, they must have been asked the question before. If you are going to ride this motor flat out round a track you need 100% confidence in what you have done, it feels to me you in danger of rushing this critical part of the build.
Sermon for the day over

[guest27]

Agree with Steve - for the cost of a phone call and possibly seeming to be a dolt, or having the engine implode at speed and be proved a dolt - I know what I would prefer and which would be the cheapest....

R

[andy230]

T'is done!  The email is sent!   

Will let you know their response...

...and, er, Rog?  Would you be willing and/or able to turn me up the required shims if necessary?  Possibly from the old cups??

We (the royal we!) would be most grateful... 

cheers for now, and no worries if its not on the cards!   

andy

[guest27]

Andy

Yup should be able to do that - mind I bear no responsibility if I stuff them up.... lol

R

[andy230]

Great Rog, that would be simply fantastic... 

Can you remind me of your email address?  Maybe just drop me a line to

a[dot]duncan[at]ich[dot]ucl[dot]ac[dot]uk

Probably easiest...

I will send you the bits I have as you may well be able to make em from these?  Or do you need me to gt you some stock??

I have both bottom and top spring retainers.

Cheers for now matey, this would solve a lot of problems.

a

[andy230]

T'is done!  The email is sent!   

Will let you know their response...

Here it is:

That valve spring kit has never been a large volume seller, so when we ran 
out of the original top retainers we decided to alter a higher volume  retainer
to make the 2067's(top ret in 120-Y kit).  That top is about 0.5mm  taller
than my original sample. 
 
Even though it increased the installed height it could be adjusted  using the
supplied shims and the new retainer had less mass: 7.5g compared to  11.4g
for the original.  However if the cam is a higher lift cam I would  pack the
spring to the shortest installed height.  I will start supplying  that kit with
thicker bottoms.
 
As far as the height being 1.5-2.0mm taller that does seem strange.   Are you
using the supplied keepers/valve locks?  Also whoever ported the  head did
they remove material from the seat causing the valve to "sink" farther  into the
head?  How many valve jobs have been performed on the seats(if  they are
stock seats) over time the valves will sink because of the removal of  material
from the seats? And are the new valves the correct length and have the  keeper
groove in the same position?
 
This is all I can think of because the new tops are only 0.5mm taller than 
the originals.
 
Let me know if you have any more questions or concerns
 
Regards
--------------------------

So now we know.  Best shim it!  And I also take back the suggestion of poor comms from RD, correspondance has been rapid, knowlegable and subsequently he's answered a few of my other questions.  Recommended!

andy