Jim Bowen 1 Posted July 11, 2013 A bit concerned after reading my Peter Russek VR6 engine repair book last night. It mentions you must follow a procedure when releasing the camshafts to avoid cam shaft distortion caused by the pressure of the valve springs. I didn't know this and have already removed my cams, didn't follow any procedure, i just undid the nuts and left the cap furthest away from the sprocket end on so the cams didn't fall off. And i even undid the nut with my electric impact wrench. Is this really a concern?, seemed to be quite important and the fact its mentioned twice got me worried. Can i tell if my cams are distorted? Quote Share this post Link to post Share on other sites
fla 9 Posted July 11, 2013 tbh I would be surprised if the cam springs could distort the camshaft - they're pretty thick solid steel bars! iirc there was a sequence in tightening the cam caps though. Quote Share this post Link to post Share on other sites
Dox 22 Posted July 11, 2013 Its good practice to undo in the opposite way you tighten them (usually a circular diagonal motion from the centre out when tightening, outside working in when removing the cams). The chance of any damage being done is tiny unless the cams have been used to lift the head off the block? Quote Share this post Link to post Share on other sites
Hatton VR6 0 Posted July 11, 2013 Hi, I would doubt if you have distorted the camshaft. The idea of the tightening / loosening sequence is to minimise the stresses on the cam shaft when fitted or removed as it will not sit flat with the valves pushing up on the lobes on the cam shaft. For example the sequence is used to prevent clamping both ends down and the valves pushing up in the centre and then stress being induced when you then clamp the centre down as the cam shaft may alter how it sits as you clamp it down. If you tighten from the centre out diametrically this reduces these stresses as the outer ends of the shaft are free to move as it is fastened into place. I would loosen the all the caps in the correct sequence and then torque them down with a manual torque wrench in the correct sequence so that you have not induced any extra stresses into the cam shaft. This will allow the shaft to sit correctly when tightened. It may also be prudent to ensure that there is no tension on the timing chains when you torque the camshaft back down. Quote Share this post Link to post Share on other sites
beastie4126 0 Posted July 11, 2013 Didn't you have a nice set of 263's waiting to go in anyway? perfect excuse to use them now. Quote Share this post Link to post Share on other sites
Jim Bowen 1 Posted July 12, 2013 I already using the 263 cams in the car at the moment, i am rebuilding the engine i took out. Just not sure if i'd prefer the cams or the money for something else. Was quite happy without the cams and need to buy some new valves & guides, new timing chains and tensioners, get the head skimmed/cleaned, and possibly a new cat. I didn't notice a correct sequence for undoing the cams, i just undid them trying not to let them fall, didn't take the sprockets off either so were quite heavy on one end ---------- Post added at 9:22 AM ---------- Previous post was at 9:21 AM ---------- I already using the 263 cams in the car at the moment, i am rebuilding the engine i took out. Just not sure if i'd prefer the cams or the money for something else. Was quite happy without the cams and need to buy some new valves & guides, new timing chains and tensioners, get the head skimmed/cleaned, and possibly a new cat. I didn't notice a correct sequence for undoing the cams, i just undid them trying not to let them fall, didn't take the sprockets off either so were quite heavy on one end Quote Share this post Link to post Share on other sites
Roger Blassberg 0 Posted July 12, 2013 Most unlikely that the camshaft has been bent; I would think that any damage from uneven tightening/untightening just might be to the soft metal in the camshaft bearings, but you would have to be fairly brutal for this to happen. To bend the camshaft beyond its elastic limit (so that it does not recover when the stress is relaxed) would require a much greater force than the valve springs could impose. Best wishes RB Quote Share this post Link to post Share on other sites
Jim Bowen 1 Posted July 12, 2013 I think i will stop worrying about it then and just get on with it. Quote Share this post Link to post Share on other sites
Stonejag 10 Posted July 13, 2013 Head skimming is really cheap - as in £20 - don't sell the 263s over it! Likewise cleaning my spare head wasn't dear. Just be sure to be meticulous about cleaning it up afterwards as there'll be lots of grit in the tiny spaces inside and in threaded surfaces etc. Go over it with an airline and then vacuum, then airline etc until no more comes out. When reassembling, if any threaded components feel gritty as you do them up then stop and do it again! If you spread it out over a few months it also seems much cheaper ;) Stone Quote Share this post Link to post Share on other sites
