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MG MGF Technical - Which cams are in the 135?
|I understand MGF 135 is hotter cams with standard head but the Elise 135 is a worked head with standard cams...|
Can anyone tell me the spec of the MGF 135 cams?
Take a look at the discussion on this thread
|More detail on the TF135 cam here: http://www.mgf.ultimatemg.com/group2/engines/index.htm|
If you are planning on fitting it to an EU2 engine with distributor based ignition, you'll also need a distributor spiggot - but more details are on the link above...
|Just to reitterate the warning I gave on the other thread. YOU CANNOT INCREASE THE LIFT OF YOUR K SERIES ENGINE ABOVE 8.8 mm WITHOUT CHANGING THE VALVE SPRING. LGL10008 was designed for only 8.2 mm lift, so is being pushed at 8.8. Above that it will be overstressed and may in fact go coilbound on worst case tolorance. The factory definatly fit a different spring. I believe it is LGL10024.|
|Paul, been doing some checking and have found that Piper and Kent recommend a maximum lift of 9.5mm and 10.0mm respectively for the STANDARD valve springs. What is your feeling about this, as I am sure that there are quite a few K-series engines running with (for example) BP270H cams (most in Lotus Elise) and using the original LGL10008 valve springs?|
|Well I don't have the drawings in front of me, but I'll tell you what I remember. I designed a 8.2 mm lift cam when K series TBI was launched in Rover 200. I also worked with the supplier Tempered Spring of Sheffield on LGL100008. It was definitly designed for only 8.2 mm, the rule we used was that at full lift we would have half a wire diameter coil clearance. I belive the wire size is 3.6 mm so at the nominal condition there would be a coil clearance of 1.8 mm. You can see that with a 10 mm lift cam you would be solid at nominal tolerance condition. If you do a tolerance stack on fitted length you find that its about +/- 1 mm hence the stroke of the hydraulic tappet has to be more than this about nominal. The stress at full lift has to be less than 900 N/mm2 and the strss at fitted should not be more than 500 N/mm2 less than the full lift stress. The stress at solid should be less than 1100 N/mm2. When myself and a chap called Paddy designed the 8.8mm lft cam we found that LGL 100008 still squeezed within these rules, so we stuck with it. However when you increase the lift further the full lift stress will tend towards the solid stress so the range will increase above the 500 N/mm2 limit making a fatigue failure likely. All cams that employ greater lift than 8.8 require a different spring LGL100024 (I think). The VVT head has this spring along with the big valves and ports. When I see Keith I'll confirm this.|
|That would be very helpful, thanks Paul - and thanks too for the very clear explanation regarding the design specs of the original valve spring. :o)|
BTW, haven't been able to track LGL100024 in the parts catalogue - and the VVC valve spring is listed under LGL100460 - could this be the spring you are indicating?
This thread was discussed between 18/02/2005 and 24/02/2005
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