Digsy Posted July 24, 2006 Share Posted July 24, 2006 I'd say it was nothing to do with welding, it's either been droped and a possibly invisible fracture started, and the act of tightening the corner fastener has cause a piece to break off, or it's been overtightened. I well all manner of alloy castings and they don't crack due to this process. Except it shound't be possible to overtighten an isolated camcover fixing, because they usually have compresion limiters built in. You do them up like any other bolt but the limiter prevents any excessive bending load going intot he camcover. Quote Link to comment Share on other sites More sharing options...
supradibbs Posted July 24, 2006 Share Posted July 24, 2006 Except it shound't be possible to overtighten an isolated camcover fixing, because they usually have compresion limiters built in. You do them up like any other bolt but the limiter prevents any excessive bending load going intot he camcover. what???????? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 24, 2006 Share Posted July 24, 2006 Correct, the stock fasteners have a shoulder on them that contacts the head surface when the oil seepage washer is fully compressed, but maybe he didn't use the OE fasteners? Quote Link to comment Share on other sites More sharing options...
supradibbs Posted July 24, 2006 Share Posted July 24, 2006 Correct, the stock fasteners have a shoulder on them that contacts the head surface when the oil seepage washer is fully compressed, but maybe he didn't use the OE fasteners? i take it you mean the rubber on the bottom off the washer its only rubber that will just expand out if i rememer correctly manual recommends about 15-20 inch pounds i have been able to tighten way behond that Quote Link to comment Share on other sites More sharing options...
Prof. Monkey Posted July 24, 2006 Author Share Posted July 24, 2006 Correct, the stock fasteners have a shoulder on them that contacts the head surface when the oil seepage washer is fully compressed, but maybe he didn't use the OE fasteners? I did use the OE fasteners.... All I want is some intact covers! Quote Link to comment Share on other sites More sharing options...
supradibbs Posted July 24, 2006 Share Posted July 24, 2006 I did use the OE fasteners.... All I want is some intact covers! yes and am trying to sort it darren but you cant just assume its my responsiabilty to do so with looking at them first,i have said if am in some way liable then i will pay without issue i have pmd you my address please return it too me so i can have my fabricator inspect it Quote Link to comment Share on other sites More sharing options...
Digsy Posted July 24, 2006 Share Posted July 24, 2006 Right - here's the full description. I'm assuming that the Supra camcover fixings are the same because all the isolated camcover fixings I've ever seen are the same and no one has posted up a pic of the Supra one yet. Isolated camcovers are not bolted rigidly to anything. The float in between two peices of rubber - one supporting it from the bottom and one holding it down from the top. The bottom isolator is the camcover seal. The top is a rubber bush or washer under the head of the camcover bolt. Therefore when you do up the camcover bolt, allthe contacts the camcover casting is rubber, see? The camcover is sandwiched in between. The problem is that if you used a normal bolt to close this joint, then you could go on and on and on tightening it until either the camcover touched the head (which defeats the object of having an isolated cover) or something broke. What you actually want is to limit the amount of compression you put into the rubber mechanically, so you can give the production line worker a spanner and say "just do that bolt up to 8Nm" rather than "do that bolt up until the seal starts to compress, but not too much or something might break". Say the "relaxed" stack of seal, camvover and washer is 20mm tall, then the camcover fixing will have a shoulder on it (as Chris mentioned) maybe 18mm tall, so when you do the bolt up the whole seal and washer will compress by 2mm in total and then go solid. If you try to tighten it furthert then you will strip the thread or break the bolt rather then crack the camcover. Quote Link to comment Share on other sites More sharing options...
Prof. Monkey Posted July 24, 2006 Author Share Posted July 24, 2006 Say the "relaxed" stack of seal, camvover and washer is 20mm tall, then the camcover fixing will have a shoulder on it (as Chris mentioned) maybe 18mm tall, so when you do the bolt up the whole seal and washer will compress by 2mm in total and then go solid. If you try to tighten it furthert then you will strip the thread or break the bolt rather then crack the camcover. Agreed! That is what normally happens, bolts are not prepared for large torsional forces and can crack. Quote Link to comment Share on other sites More sharing options...
Prof. Monkey Posted July 26, 2006 Author Share Posted July 26, 2006 Got the cam covers off, had a look at the damage, wondered, what you guys think? The pencil is there to show where the shaft is that the plastic cover screw into.... These where what were filled.. Quote Link to comment Share on other sites More sharing options...
TLicense Posted July 26, 2006 Share Posted July 26, 2006 Just a note, the fasteners for the cam cover should be torqued to 5.4Nm which is very little. In fact it's not a lot tighter than finger tight, and most general use torque wrenches don't go as far down as this. Other than that, that cam cover is knackered, you're going to need a new one. Quote Link to comment Share on other sites More sharing options...
TLicense Posted July 26, 2006 Share Posted July 26, 2006 Can someone post a picture ot a standard camcover fixing, please? Ta-da..... Quote Link to comment Share on other sites More sharing options...
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