Main Menu

Valve question

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

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Marc Fenner

2. The valve is getting to hot. One idea was to drill the fins on the head which increases the surface area.
3. We need to think about changing the valve retainers and make them lighter. Maybe titanium???

There where a few other things too that they said to look into. All the above stuff is stuff they mentioned to me and i may have cut corners. The old chinese wispers things.

They are happy to look at the info we have. I have printed of Andys cam profile info and club rules for them to look at.
These guys are known for being the best in the uk even europe. Who knows they may be able to help!
Any other info i can pass onto them would be useful.

Sean

Quote from: Paul Robertson on September 19, 2008, 11:54:43
Andy Bull has just finished plotting the standard profile against the club profile so we can scrutineer the cam without an engine strip and it looks almost identical, other than a flatter peak on the club cam giving longer full lift.

just spotted the plotting post over in tech.
Surley the top of the graph isnt going to be the problem bit is it? ,the much steeper opening and more importantly closing profiles... the area in the last 1mm of closing on the inlet looks "intresting". Assuming there is still a bit of work to do with plotting accuracy innitially there appears to be a much softer close on the Std cam with that extended curve :-\

Sean

Rambo

Many years ago I overhauled a few Citroen SM engines, and they had sodium-cooled exhaust valves, which are hollow stemmed with welded heads. One of them had a head come off while being ground, and non cooled one piece stainless valves are the replacements. The problem there was due to corosion at the weld, and as these engines were also fitted to the Maserati Merak a lot of engines were badly damaged when they were started after a few years hybernation. NEVER try to start one of these cars if it has been dormant without knowing if it has the stainless valves. Could our recent problems be that everyone fitted new valves as a precaution after 2004, and those valves are now coming to the end of their lives with the current cam?

Trevor Williams

I have just finished measuring a load of valve springs and discovered that three of the new ones that I have are very low.
They didn't even get to 100psi.
So, bit of free advice - check your valve spring rates!
Some days, it's REALLY difficult being me!

Paul Robertson

 I have just tested over 120 second hand and previously raced valve springs ,there were less than 10% that were within 5psi of the recommended pressure to be used singly.
I would suggest that if you are running single valve springs you are at great risk of damaging your engine and that valve springs should be checked / changed after they have done a couple of seasons racing,especially if the engine has been used for the 24hr race .I would also suggest that all valves should have inner and outer valve springs fitted.

Paul

these are my suggestions not those of the classic 2cv racing club

Derek Coghill

Paul, Norry also recommmends double springs but suggests that they be changed even more frequently.

Martin Harrold

Paul, Trev:

I've found that a local firm which makes springs for one of the products we manufacture can also test (and make) valve springs. So, we are getting them to test some we have. I read that 100lb is a minimum target figure. Do you know what the spec figures / range are for the main valve spring and for an inner valve spring ?

Out of interest, I asked them to check test some suspension springs we've had from their friends at SpringCoil. Those springs have the rating written on them. They tell me that they cannot test them but they can do a calculation. They say (and I can't believe that they are correct) that there is only one machine in the UK big enough to actually test those springs, which is at some kind of institute in Sheffield.
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

Paul Robertson

Martin,you need to be looking at 150psi for the main spring at installed height +full lift or by my calculation when the spring is 27mm long.The inner when fitted inside the outer should give an increase of 20-30 psi.So combined pressure should be 170/180psi.
Springcoil have their two test rigs (one computerised, one manual)which i have seen them use, they have one employee that all he does is measure spring pressures.
HTH Paul

Martin Harrold

Paul - thanks. I'll keep you posted. Out of interest, have SpringCoil ever been asked to make valve springs?
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

Paul Robertson