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Valve question

Started by Trevor Williams, August 26, 2008, 08:14:09

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Trevor Williams

Paul
If the club are getting the valves made, can the be made to the exact specification in the regulations? That way it would then be pointless trying to do anything else to them and they almost become a standard item
I'll take enough for 5 engines!
Trevor
Some days, it's REALLY difficult being me!

Martin Harrold

We'll have enough for three engines
2CV Team LION
2CVParts.com Champions 2014, 2015, 2018, 2019, 2021 & 2022
CITROEN 2CV 24 Hour race winners, 2014, 2015, 2016, 2017, 2020, 2021 & 2022
m: 07973 303982

Martin Sadler

I'm new to these 2cv things and are severely dismayed at what seems to be an onging problem with these engines. I've just dismantled one of Keith Shoebridges engines - race engine no 3 (one that didnt totally distroy its self) to find the widely reported inlet valve nicks/chips distroyed head, piston, barrel etc. Our no 1 race engine totally distroyed its self and wont even make an interesting coffee table. What concernes me is that these problems go back so long - 2004. I've read all the reports in the historic forums and what we are experiancing is exactly the same. With out a doubt there is still something fundermentally wrong inside these engines and no fix has been found - or given out to all competetors.
I have given whats salvageable to my cylinderhead company to see if they can come up with ideas/remidies. Here are a few of the things they and I have come up with.-
1. the valve material is S**t - his words not mine and has no place in a racing engine. Waisted or standard. The valves in this engine were NOT waisted
2. the valve seat angles are wrong and will promote valve pounce
3. the valves are of a 2 piece construction - see 1 above.
4. the valve springs are almost coil bound on full lift and show referance marks where they have actually touched.
5. there is evidence that the inlet valve on the off side bank has hit the piston
6. on full lift at high reves with valve bounce a posibility, have the valves touched?

Many of these points have been made recently and in also in 2004, and I cant see why the technical commitee hasnt investigated this in depth and made parts available to all that will stop it happening. They have stipulated a control cam why not go further so that if there is a fix, make it available to all via the club - they do it in NASCAR in the states and it keeps the racing fast, reliable and cuts out any cheating/advantage by one team over another.

I plan over the next few days to measure the cam lift , duration, and check timing. This engine does not run a vernier so the siming should be standard. I will be looking specifically to see if the off side inlet lobe is ground slightly advanced over the near side, if it is the club needs to talk to Kent at depth about a redesign. Before any body asks yes I did check the valve cleanance before strip down and they were all ok.

Martin
07867.798680


Mary Lindsay

We did wonder if it was because the valve appears to be made of two different metals. We found that part of the valve that broke on our engine last year was magnetic and part was not.

Paul Robertson

#34
We have had valve problems for over 15 years now ,the move to the waisted valves was made as they were the only thing available as a replacement for the standard two piece valve .This appeared to have stopped the problem until this season,when for whatever reason we appear to be back to square one.
The one piece stainless valves will not be ready until after mallory and will be made to original seat angles as per our regs.
I have timed more camshafts than most in the club and can say i have yet to find a cam ground outside of kent's tolerances and most to be spot on.
If you are a club member and wish the technical committee to investigate something with a view to a rule change please contact them and request they do so.

Martin Sadler

HI Paul,
I'm not a member yet but I will be next year.
Now back to valves. Have you found a reason or have any thoughts why the off side cylinder seems to be the one that fails / has the valve marks in the piston - not the nearside. All 3 of Keiths race engines failed on the off side? I can find nothing wrong in the crank area, rods etc
Martin
07867.798680

Andrew Bull

Valve material may well be sh1t, but should the tech committee could have one analysed? Many Test Labs can perform material composition analysis if required.  Also Universities have a vast engineering resource. 

Offside of the engine has that large heat sink bolted on.  (AKNA The alternator).

If you have evidence of Coil Binding on the springs then that points to one of three things.  Rocker Ratio / modified rocker foot.  Valve float off the peak of the lobe.  Knackered springs. Given Paul's comments about Cams I havent included the grind as a possible cause.  Timing could be, if the engines dont have verniers then the standard Citroen manufacturing tolerances are still applicable to the Timing of the cam, and you cant dial it in to the perfect timing.  One of the reasons for the control cam.

The Cam itself may also show signs of an impact wear area after the peak where the follower comes back into contact after float.

If you have coil bound the springs then i should check the rocker arms, pushrods, and cam followers. 

The other consideration is the springs.  Were they new.  Were they Tested?  double? 

Your Points 4,5,and 6 all point to high rev damage though.  If you are seeing evidence of touching on other valves in the engine then there is a strong possibility that high revs has caused the initial tweak to the valve, thus weakening it.  Have you calibrated the rev counter?

Points to note for the Tech committee. 
1) Stainless Valves -      on order PR
2) Investigate material properties of current valves
3) Publish / obtain / calculate, recomended Valve spring pressures.  Kent Cams may help?
4) Investigate progressive springs and rates.   
Andrew Bull
Tête Rouge Racing with Habitabull & Propolis
Rookie Champion       2022
team champions         1998 2000 2008 2009 2013
24hr winners               2005 2006 2009 2010 
championship winner 2006 2007 2008 2009 2010 2011 2013

mark turner Whitwell Motorsport

Replying to the many questions/comments on this seemingly frustrating subject!
An order was placed yesterday for 400 one piece stainless steel valves which will not be available untill
after the final 2x rounds at Mallory park.
Going onto some of the points raised by Andy regarding the tech comittee,
current valve materials:-
I am speaking to York university as to having currently available valves tested,i will keep everybody informed as progress is made.
Progressive valve springs:-
I have tested with progressive valve springs and have found no difference in performance or reliability
over standard double springs.
Valve spring rates:-
Valve spring rates are different from valve to valve, mainly due to valve weight but cam profile and rocker
ratio and max rpm come into the equation.I will post some recomendations in the next few days for the
current valves.
Valve springs going coil bound:-
If your valves are installed to standard citroen spec, the valve spring cannot become coil bound!
Valve bounce/too many revs shows the same markings on the valve springs as going coilbound.
Suggestions:-Check insalled heights/fit a rev limiter!
I am currently testing the effects of heat build-up on all types of valves available because i am convinced
that most people are running their engines too hot, the car that won the 24hr this year ran a 9 blade fan
and suffered no engine damage whatsoever.We ran a 6 blade fan and still over heated the engine on one
side.
I will post my results in due coarse.
Mark. Whitwell Motorsport.
                 

Winners of the Snetterton 24hr 2011
Winners of the Snetterton 24hr 2012

Andrew Bull

Thanks for the Info Mark.  I look forward to seeing some of the results. 

The heat thing is a bit odd.  We have run 3 blade for a good few years now including all this year, but did a cam follower not a valve in the 24hr.  Although if a valve got sticky due to heat then this could have the result of knocking the bottom out of a follower. 

For all intersted parties there is a very useful explanatory guide on http://www.aa1car.com/library/ar1192.htm

I know its talking about yank tanks but the thoeries are the same and we are running a hemi head anyway. It's an interesting lunch time read and talks frequently about valve float, seat bounce, and bending of stems causing fatigue failures when attention is not paid to the alignments and seat cutting, and valve guide wear and alignments.

Cheers
Andrew Bull
Tête Rouge Racing with Habitabull & Propolis
Rookie Champion       2022
team champions         1998 2000 2008 2009 2013
24hr winners               2005 2006 2009 2010 
championship winner 2006 2007 2008 2009 2010 2011 2013

Geoff Archer

My engine from pete was the exhaust valve, found the head in the sump
NES 2cv Speed Shop
+44 (0)1609 771313

Martin Sadler

Andrew
aa1car.com excellent site with a lot of very relavent facts and tips
Martin

Andrew Bull

Martin, I think ive just given my secret away.  I know feck all really, just read alot. 

Mark, Do you know what grade of stainless material they will be made from.  You know the DIN / EN spec or designation.

Cheers 
Andrew Bull
Tête Rouge Racing with Habitabull & Propolis
Rookie Champion       2022
team champions         1998 2000 2008 2009 2013
24hr winners               2005 2006 2009 2010 
championship winner 2006 2007 2008 2009 2010 2011 2013

mark turner Whitwell Motorsport

We (as a club/tech comittee/management comittee) are having discussions with the manufacturers as to
what is the correct material shape and profile for our needs. We are not going to rush into a product that is not what we want! I believe experiance and research count for an awfull lot. Time and testing will tell us
everything,so stay tuned! We will keep you all informed on progress ;D
Winners of the Snetterton 24hr 2011
Winners of the Snetterton 24hr 2012

Bas

Quote from: Andrew Bull on September 03, 2008, 16:59:55
Martin, I think ive just given my secret away.  I know feck all really, just read alot. 

Mark, Do you know what grade of stainless material they will be made from.  You know the DIN / EN spec or designation.

Cheers 
bully think the grade should be 21 4n austenitic stainless thats 21% chrome  4%nickel         very tough stuff
Tete Rouge Racing since 1993

Bas

dont know about the valves being waisted but i certainly was! how about watching the sun come up again pete?also thought gadget needed rear view mirrors in our garage sunday night!  laugh i nearly bust a gut!
Tete Rouge Racing since 1993