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    Engine rebuild update

    By way of an update from some of my previous postings, I thought I would share the key details from my engine rebuild. It started back in the first lockdown last March, when the timing seemed good to deal with the top end of my engine. Working with my trusted mechanics John and Chris at Old Forge Motors in Harrogate, I sourced all the necessary parts and they did the skilled stuff! Heads skimmed and polished, new valve gear, new timing chain kit using the German type. All good when put back together and it ran well throughout the summer and autumn, but with the oil pressure dropping slowly but surely. After various tests the inevitable conclusion had to be reached: the bottom end of the engine also needed addressing.

    Hindsight is a wonderful thing and it would have been better to do the whole job in one go. But this way it provided us with another project during the winter and the associated lock-down. As before, I sourced the parts and Old Forge did most of the heavy lifting – literally this time as the engine had to come out. Drake Engine Re-manufacturers in Bradford (W. Yorks) did the rebore and sourced the bearings, pistons and rings at +40 thou, plus they balanced the crankshaft together with all the associated parts through to the clutch plate. Ah, the crankshaft. It turned out that mine was already at +60 thou so I had to find another. Paul McLaughlin at Stag Classics (Alton, Hants) came up trumps with a reground and toughened one he had out the back, complete with bearings. The jackshaft and water pump were fully checked and retained as they are both in good working order. A new (County) oil pump was fitted with the replacement spring.

    Finally, I decided to ditch the Strombergs and fit Chris Spain’s Stagweber 38 conversion with the optional active breather system to better replicate the Stromberg crankcase vacuum set-up. I’ve been back on the road for about 6 weeks now and all is running really well. An initial oil leak was tracked down to hardened ‘half moon’ black end plugs under one of the rocker covers, so all four replaced and something we missed first time round. It runs smoother, with more power, and better economy although yet to be fully measured. The Stagweber conversion is a definite improvement, with better pick-up, idling and choke operation as well as better performance. Have just changed the oil and filter after 750 miles as a precaution – lots of new metal in there! Cost? Don’t ask, but less than I have been quoted before by a couple of the Stag specialists and it should be good for another 150,000 miles and see me out! Old Forge work on classic cars of all sorts and have rebuilt several Stag engines over the years. Parts came from various sources including James Paddock, Robsport, LD Parts, and Rimmers. Wherever possible I went for better quality options, e.g. timing chains and head gaskets.

    Paul

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    Mk 2 1975 TV8 Mimosa

    #2
    Nice to hear you cracked it in the end Paul I had a similar experience as you mine was running hot when I bought it so I removed the heads ( they came off easy) and refitted, it ran loverly for the rest of the summer until the mot ran out and I fitted an oil pressure gauge and it had 0 on tick over, so bit the bullet and like you had everything done inc the work on the heads,

    Comment


      #3
      When I changed my timing chain, I was told by the supplier that their experience of people coming back was that the German chains tended not to stretch but when they go old would snap with no warning, whereas the UK chains would stretch then make a distinctive noise and so you new you had to change it before any major damage occurred..

      Have other people hear this and is it true?

      Dave

      Comment


        #4
        I’ve heard that one before, but dismissed it as never heard of chains breaking, unless caused by seizure of another part.
        Last edited by KOY 23; 9 June 2021, 21:35.

        Comment


          #5
          A few years ago I did a forum poll about timing chain failures ( put timing chain poll in the search box, it is a few down the list showing as Which broke first?)

          Basically the chain snapping without warning is unusual, somewhere between 2/3 and 3/4 of breakages (depending whether you include the Dolomite or not) were caused by the jackshaft seizing first. A good quality chain may even shear the jackshaft dowel without breaking the chain and cause much less damage. The only certainty is that cheaper chains will stretch and cause even faster wear on the butter soft crank sprockets that are available these days.
          All that metal that is lost from the sprockets has to go somewhere. It isn't all caught by the filter as some goes through the bypass valve which is why I now favour magnetic sump plugs.

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

          Comment


            #6
            Where can you get a magnetic sump plug I would like to fit one

            Comment


              #7
              Interesting Neil. My chains and sprockets weren't too bad but were over the 25,000 mile mark so decided to change them along with the other work. However, knowing about the butter sprocket issue, we decided on balance to retain the old sprockets as they were in good nick. I like the sound of the magnetic sump plug, will look one out. Paul
              Mk 2 1975 TV8 Mimosa

              Comment


                #8
                I would also like to buy a magnetic sump plug. Any recommendations as to where to buy one? Thanks M

                Comment


                  #9
                  Originally posted by Bakdraft007 View Post
                  When I changed my timing chain, I was told by the supplier that their experience of people coming back was that the German chains tended not to stretch but when they go old would snap with no warning, whereas the UK chains would stretch then make a distinctive noise and so you new you had to change it before any major damage occurred..

                  Have other people hear this and is it true?

                  Dave
                  That old chestnut! Question 1 is what are "UK" chains?

                  I posted this in 2011 when I was learning Stag!

                  Originally posted by dasadrew View Post

                  ROLON is the trademark owned by the Indian chain manufacturer L.G.Balakrishnan & Bros Ltd. (LGB)

                  Renold is - as far as I know - the original UK manufacturer of the Stag chain gear.

                  Renold and LGB have now formed a joint venture to sell chains with the LGB trademark "ROLON". Whether these are made by Renold or LGB I don't know. I guess they continue to be made in India.

                  As for the German chains being risky as they are pre-stretched, this is a quote from the Renold/LGB ROLON site:

                  Preloading of the chain: Rolon chain is preloaded in special fixtures. This enhances resistance against initial elongation and fatigue.

                  The IWIS story is simpler. German company founded in 1916 and still in the hands of the founder's descendants.
                  The answer isn't 42, it's 1/137

                  Comment


                    #10
                    I was very aware of 'that old chestnut' re the German v 'British' timing chains. I read stuff on here and talked to area SOC owners and decided to go the IWIS route. I drive my Stag quite robustly and cover around 3,000 - 5,000 miles a year. Assuming an expected 25,000 minimum lifespan for the chains, it's going to take me around 5 - 8 years to really know the answer. I might be in a motorised bath-chair before the chains give up!
                    Mk 2 1975 TV8 Mimosa

                    Comment


                      #11
                      Paul, "German chains" is a very unspecific term. If you use the genuine German BMW chains made by IWIS I don't see any reason why these should fail. BMW even doesn' have an istruction for replacing the chains during the car live
                      More important is Neil's hint concerning the butter soft sprockets. I have already posted the IWIS hardening specs here in Jan 2020. Just follow their advice in order to avoid wear.
                      And another weak point ist the "rubber" layer on the tensioners. Modern systems are covered with a glass fiber filled plastic. (a topic for SOCTFL?)

                      Klaus

                      IWIS Härtevorschrift - hardening specs.jpg
                      Last edited by Klaus Schlueter; 10 June 2021, 16:15.

                      Comment


                        #12
                        Originally posted by markmark2 View Post
                        I would also like to buy a magnetic sump plug. Any recommendations as to where to buy one? Thanks M
                        Not sure how long it will stay magnetic, but you can make your current plug magnetic. Tools I've done usually stay magnetic for at least a year, so it should be enough to get to the next oil change.

                        This isn't going to be in any OSHA or Health and Safety approved "how to" book you come across, but it works great on magnetizing ferrous metal screwdrivers or other tools. I can also see screwdrivers are much easier to work with than any sump plug.
                        1. You're on your own with this. If you think you are going to blow up, you probably will, so stop. If you're afraid of electrickery, stop. If your wife just reupped your life insurance, she'll say keep going, but you should probably stop. Otherwise, march on.
                        2. Be careful - wear safety goggles.
                        3. Get a 12v car battery. Must be in good working order and at least showing 12 volts
                        4. grab a ~2' piece of stranded wire. Can be #12, #14 whatever you have really. Trim off ~1/4" of the insulation from each end
                        5. tightly coil the wire around the sump plug, leaving around 6-8" tags on each end. You will have coils wrapped over coils
                        6. very briefly touching one tag end to the + and - terminals. You can hold one end on the - terminal and brush the other tag end across the + terminal. DO NOT HOLD BOTH ENDS ON THE TERMINALS
                        7. Three or four quick brushes across the terminal is all that it should take to magnetize the plug
                        Expect it to spark, so that is why I say brush the end across the terminal. Be forewarned that the wire will most definitely heat up. Did I mention BRUSHING the end across the terminal? The biggest problem I can foresee is the tiny size of the sump plug. You can always just use smaller gauged wire I suppose.
                        Last edited by RNF; 10 June 2021, 18:47.
                        John

                        Comment


                          #13
                          Magnetic sump plugs for Stags used to be available on eBay, with the correct tapered thread. I bought one about 20 years ago and it is still strongly magnetic.
                          Dave
                          1974 Mk2, ZF Auto, 3.45 Diff, Datsun Driveshafts. Stag owner/maintainer since 1989.

                          Comment


                            #14
                            Originally posted by flying farmer View Post
                            A few years ago I did a forum poll about timing chain failures ( put timing chain poll in the search box, it is a few down the list showing as Which broke first?)

                            Basically the chain snapping without warning is unusual, somewhere between 2/3 and 3/4 of breakages (depending whether you include the Dolomite or not) were caused by the jackshaft seizing first. A good quality chain may even shear the jackshaft dowel without breaking the chain and cause much less damage. The only certainty is that cheaper chains will stretch and cause even faster wear on the butter soft crank sprockets that are available these days.
                            All that metal that is lost from the sprockets has to go somewhere. It isn't all caught by the filter as some goes through the bypass valve which is why I now favour magnetic sump plugs.

                            Neil
                            There seems to be a general agreement that the crankshaft sprockets are the problem here. All the horror pictures are of crank sprockets with major tooth loss. As Neil wisely says "butter soft crank sprockets". My own experience is that it is only the crank sprockets that wear visibly. On my last front end rebuild I was shocked how close I had come to disaster (after 60K miles). All other components were fine. Including tensioners, guides, chains and camshaft sprockets. I changed them anyway!

                            So I suppose the question is, why can't we get camshaft sprockets made out of a harder material? I am not in the auto supply world, but is anyone familiar with how you get these parts made in small batches? I am sure there would be plenty of takers including me. I would be happy to organise it.

                            Mike

                            Comment


                              #15
                              Maybe speak with the club tooling fund?
                              Header tanks - you can't beat a bit of bling.

                              Comment

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