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New Con Rod bolts and nuts when rebuilding the engine ?

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    New Con Rod bolts and nuts when rebuilding the engine ?

    Hello guys,
    I have been recommended to replace all bolts and nuts of the con rods before re-assembling the engine.
    Apparently this is always necessary and prescripted when rebuilding modern engines, but does this rule "stick" also to classic cars engines and in particular for our Stag V8 ?
    Thanks in advance for a short advice.
    Best regards
    Dave

    #2
    Dave.
    Others may disagree, but as they are not "Stretch" bolts, I have never felt the need to replace them, unless there is a problem such as a badly worn big end. As far as I know, none of the ones I re used have ever failed.
    Mike.

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      #3
      it depends on how bad the engine was before stripdown, also the mileage.

      Small ends can be replaced, these will stop the small end tinkling noise.

      More important though, if the old bearing shells were shagged out then there is a possibility that the conrod ends have gone oval.

      I bought a refurb set from Faversham classics when I was doing Giles' engine rebuild
      Stags and Range Rover Classics - I must be a loony

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        #4
        It comes under the category of " good engineering practice". If you have spent a fortune on machine shop rebore, crank regrind, new pistons etc why risk a bolt failure. You don't know if these bolts have been over torqued and stretched at some time
        John
        1978 Stag Brooklands Green

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          #5
          don't know if they do them but if you replace and ARP are available go for them

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            #6
            I have read of uprated bolts being available but that they are so tight to fit the big ends need re-machining back to round after fitting.

            As mentioned above they are not stretch bolts so don't need to be replaced. However, when rebuilding one engine I found one rod bolt didn't feel right as it approached full torque. It felt like it was stretching so I binned it and replaced it with a second hand one from a spare set of rods I had in stock.

            I suppose it would be possible to measure the entire set for length before fitting to the engine. I would have thought they would all be within a reasonable range of length, an odd one would suggest over tightening at some point.

            Neil
            Neil
            TV8, efi, fast road cams and home built manifolds. 246bhp 220lbft torque

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              #7
              Yes agree . For the cost of a new set compared to the cost of your rebuild its a small price to pay for the reassurance. When I rebuild an engine I all ways use, where possible, ARP fasteners. It is definitely good practice.

              ARP 2000 range are possible the best for the rods, i used them on mine even thought the rods came with ARP 8740 bolts as standard, it raised the safety margin 25%.

              Not 100% sure but the ARP maybe these (two set) https://arp-bolts.com/kits/arpkit-de...?RecordID=1239 If not there not the right ones theres bound to be some that are correct fittment.

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                #8
                Sorry, slightly off topic, how much would a set of refurb conrods cost ?

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                  #9
                  Call Trevor at Faversham classics
                  Stags and Range Rover Classics - I must be a loony

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                    #10
                    thanks Richard, will do.

                    Didn't you get recon conrods for your friends Stag ?

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                      #11
                      Originally posted by flying farmer View Post
                      I have read of uprated bolts being available but that they are so tight to fit the big ends need re-machining back to round

                      Neil
                      I have a set of new bolts, I changed one and it was very very tight. I read here that bolt failure was unusual and decided to not change the rest. I pulled the bolt in with the nut but needed to go way over recommended torque to get it in, and still I was worried if it was all the way settled. If I have a failed bolt it will probably be the one I changed... Now if you have a press it will be another matter.
                      Last edited by Ian928; 31st July 2020, 14:17.
                      Kirsti & Ian in Norway
                      1973 Stag Mk2 (ex-USA), Mallard Blue, TV8 engine, Manual O/D

                      Comment


                        #12
                        I bought a set of Conrod bolts & nuts but only used one to replace a stretched thread. The refurb of the little end bush in the rod was less straightforward...required super accuracy honing I found & the machinery to do that isn’t common.
                        There are 2 secrets to staying on top :- 1. Don't give everything away.
                        2.

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                          #13
                          A word of caution - some of my con-rod bolts looked a little scuffed so I thought I replace with new however when I can to torque the new ones up they were spreading and giving way as the specified torque was reached. I put the originals back on - no problem. New is good if the quality is as or better than OE!

                          Peter

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