Jake Posted January 10, 2006 Share Posted January 10, 2006 I always thought that our cylinder head bols were 'Torque To Yield' and not reuseable, right? The reason I'm asking is that in Toyota's Supra Engine Repair Manual it says : Using caliper, measure cylinder head bolt diameter 2.0" (50 mm) down from bottom of bolt head. Replace cylinder head bolt if diameter is less than .421" (10.70 mm). Does this mean I can safely reuse my existing head bolts and save myself £165 or is that an unwise gamble? This engine rebuilding lark is a dear old game and £165 is not a saving to be sniffed at but obviously it would be a disaster if the bolts later failed. Any thoughts? Quote Link to comment Share on other sites More sharing options...
Miguel Posted January 10, 2006 Share Posted January 10, 2006 Always replace ..the gamble is not worth it ...specialy with what hapened to both you lumps and heat. Quote Link to comment Share on other sites More sharing options...
bromy Posted January 10, 2006 Share Posted January 10, 2006 I would have thought they are asking for a measurement to see if the bolts have stretched, but you dont really need any more problems jake so i would buy new Quote Link to comment Share on other sites More sharing options...
Jake Posted January 10, 2006 Author Share Posted January 10, 2006 Ah bollocks, I knew you guys were going to say that OK then, it seems that ARP head bolts are similarly priced to Toyota ones. Should I go for the undercut ones or are the vanilla ones more than enough? I've found a place that stocks them Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 10, 2006 Share Posted January 10, 2006 vanilla Quote Link to comment Share on other sites More sharing options...
Jake Posted January 10, 2006 Author Share Posted January 10, 2006 Thank you gentlemen. Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 10, 2006 Share Posted January 10, 2006 From what I know of the ARP bolts, they can be torqued to a point where they provide the same clamp load as the stock bolts but without yeilding. This makes them reusable but beware: Torque tightening is a much less accurate way of spefiying a bolt's preload - which is the all -important thing on critcal fasteners like main and rod caps and head bolts. When torque tightening, the final preloda depends on many factors such as cleanliness, fit and straighness of the bolt, how the torque is applied, etc. With yeild tightening the final preload only depends on the material properties of the fastener and these can be directly quality tested by the manufacturer. If the ARP bolts only give the same preload via a less accurate tightening method then I struggle to see the real world benefit. If they give more preload than stiock then I'd be worried about head warping and valve seating. Quote Link to comment Share on other sites More sharing options...
Jake Posted January 10, 2006 Author Share Posted January 10, 2006 From what I know of the ARP bolts, they can be torqued to a point where they provide the same clamp load as the stock bolts but without yeilding. This makes them reusable but beware: Torque tightening is a much less accurate way of spefiying a bolt's preload - which is the all -important thing on critcal fasteners like main and rod caps and head bolts. When torque tightening, the final preloda depends on many factors such as cleanliness, fit and straighness of the bolt, how the torque is applied, etc. With yeild tightening the final preload only depends on the material properties of the fastener and these can be directly quality tested by the manufacturer. If the ARP bolts only give the same preload via a less accurate tightening method then I struggle to see the real world benefit. If they give more preload than stiock then I'd be worried about head warping and valve seating. Well yeah but having "Stock head bolts" in my Sig's list of mods isn't going to impress anyone, is it! Quote Link to comment Share on other sites More sharing options...
Ian C Posted January 10, 2006 Share Posted January 10, 2006 Mystery thread lock removed -Ian PS it wasn't me Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 10, 2006 Share Posted January 10, 2006 Mystery thread lock removed -Ian PS it wasn't me "Thread lock". PMSL. Geddit? Geddit? Hehehehehehhhhhhh*cough* Quote Link to comment Share on other sites More sharing options...
paul mac Posted January 10, 2006 Share Posted January 10, 2006 Jake i used ARP's when i had my head off and would recommend them, i know its hard to get excited by bolts but they are lovely, i got a really good price off MVP as well, give Dusty a shout Quote Link to comment Share on other sites More sharing options...
Jake Posted January 10, 2006 Author Share Posted January 10, 2006 Cheers Paul. Right, ARP it is then. They're cheaper than the Toyota ones too Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 10, 2006 Share Posted January 10, 2006 [good humour - honestly] Always glad to see a sound engineering argument get shot down in flames in the name of bling. I dunno. Fourteen years in the automotive engine design game and I still can't convince anyone. Maybe I should have been an artist. [/good humour - honestly] Quote Link to comment Share on other sites More sharing options...
Jake Posted January 10, 2006 Author Share Posted January 10, 2006 Sorry Darren, I do respect your experience and knowledge but nearly all the big power Supras in the UK and the states use ARP bolts in preference to the stock ones so I don't think they are going to cause a problem. Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 10, 2006 Share Posted January 10, 2006 No probs, Jake. Quote Link to comment Share on other sites More sharing options...
Ian C Posted January 10, 2006 Share Posted January 10, 2006 And anyway, lighting can't strike thrice -Ian Quote Link to comment Share on other sites More sharing options...
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