julian1 Posted July 12, 2018 Share Posted July 12, 2018 HelloMy crank pulley fell off at Rockingham last week allowing the cam belt to work its way through the cover and eventually fall off. It finally came off at idle after I had driven back to the paddock. I've had the covers off now and I can turn the inlet cam pulley through about 160 degrees by hand as though there is nothing connected to it. Is this normal or have I broken something inside the VVC bit? The exhaust cam turns as I would expect it to.I was hoping to time it up, pop the belt back on and if it turned ok by hand, do a compression test to see what might have happened inside. I don't fancy doing that yet until I understand this strange pulley behaviour. thanks in advance Link to comment Share on other sites More sharing options...
SM25T Posted July 12, 2018 Share Posted July 12, 2018 Inlet cam is divided in two ... front half driven by front pulley and rear half driven by rear pulley. Link to comment Share on other sites More sharing options...
revilla Posted July 12, 2018 Share Posted July 12, 2018 Yes you can certainly normally turn the inlet cam pulley by a fair amount without it feeling like it is doing anything. The firing order is 1-3-4-2, or to think of it from a different starting point 2-1-3-4, so cylinders 1 and 2 inlet valves open 90 cam-degrees apart and then none of them are open over the rest of the cycle, meaning the front inlet cam can be turned through that part of the cycle without depressing any valves. Same is true of cylinders 3 and 4 for the rear cam. I think you'll be lucky if you haven't done something to an exhaust valve though. Fingers crossed! Link to comment Share on other sites More sharing options...
revilla Posted July 12, 2018 Share Posted July 12, 2018 Thinking about it, assuming your VVC mechs are fully retracted (as they would have been at idle) the inlet cam duration is 220 crank-degrees, or 110 cam-degrees. If the two sets of inlet valves are separated by 90 cam-degrees, the cam will be lifting a valve over 110 + 90 = 200 cam-degrees, leaving it free to turn over 360 - 200 = 160 cam-degrees (which agrees exactly with what you measured ) Link to comment Share on other sites More sharing options...
julian1 Posted July 12, 2018 Author Share Posted July 12, 2018 Thanks bothSounds like i could at least try plan A and see what happens. Link to comment Share on other sites More sharing options...
Mechanical Moz Posted July 13, 2018 Share Posted July 13, 2018 What happened to the crank pulley bolt? I'm guessing it fell out rather than snapped if you're looking to pop it back together? I'm sorry to say I'm not optimistic for you unless the crank stopped spinning within a single revolution of the belt coming off. Link to comment Share on other sites More sharing options...
julian1 Posted July 13, 2018 Author Share Posted July 13, 2018 The bolt fell out leading to everything else. I also expect there to be damage but thought I’d check just in case. Ever the optimist. If the head comes off it would be rude not to polish and port it don’t you think? Link to comment Share on other sites More sharing options...
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