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Changing Main Bearings

Discussion in 'Rover P6 Engine 4 cylinder' started by Brian-Northampton, Jun 22, 2009.

  1. Brian-Northampton

    Brian-Northampton Administrator


    As the subject says, I'd like some help and info on changing the main bearings on the 4 pot.

    Actually, you could say this is an appeal to Harvey to share his experience in a bit more detail but to quote from a previous thread that for some reason was under 'electrical' - probably because of oil pressure, Harvey said:

    I was chatting to Hermione149 this evening and we can't get our head around the rear mains, because the crank is surely held firmly by the gearbox - how do you create enough wiggle room to remove/insert the bearings?

    So, please Harvey, for the benefit of us all, to contradict the Haynes book of Lies and the workshop manual, and make my life easier this winter when I HAVE to tackle the job, can you give me the "janet and john" version as a novice mechanic.

    If I get enough information, and enough nerve to bite the bullet and tackle the job, I'll photograph it and put it in members projects AND P6 News! that's a promise.

  2. harveyp6

    harveyp6 Well-Known Member

    There really isn't much more to it than I've already said, the crank drops by enough with the belts slackened and the mains caps slackened as well. There's enough movement in either the first motion shaft (manual gearbox) or the converter to allow the upper shells to be pushed around the crank, moving towards the locating notch on the shell. If you get a lolly stick and cut off the rounded ends to 90 degrees you can give the end of the shell a tap with that if needed to get it moving.
    Personally I remove all the mains caps at the same time, as they are all marked, but slackening and removing one at a time would just eliminate any chance of a mix up. Ends have to be done one at a time as otherwise they foul on the crank.

    Ive done them on 2000/2200's for the reason I said, and on V8's to bump up the oil pressure and stop rear main seal (rope) leaks when replacing those.

    The only thing I would say is that it is the kind of job that won't tolerate not doing it correctly, but it is something that can be done, and done with relative ease if you have the confidence and competence to do it properly, but I have seen engines wrecked by people who thought they had both, but as it happens, sadly it turned out they had neither.....
  3. Brian-Northampton

    Brian-Northampton Administrator

    Thanks Harvey,

    I'm preparing myself well in advance. If I can't visualise what I need to do in my mind first, I'm not going to tackle it! I like your lolly stick tool, very good.

    How long do you reckon it takes. Well, how long would it take you to do the big ends and mains? Then I'll probably multiply that by 5 for me as I'll check, double check, photograph, read the manual.........etc etc to make sure I do it right. After all, I feel like an apprentice without having anyone looking over my shoulder :D

  4. harveyp6

    harveyp6 Well-Known Member

    If I were you I'd forget about putting time constraints on the job, just work through it in a methodical manner, and when it's done (properly) it's finished. Any time I might say would be meaningless to you, and would then just make you think you were doing it too quickly/taking too long. You won't be able to order the shells until you have one of each out anyway, so you know if it's had a regrind.

    You should get both sets of shells, a strainer gasket, and I'd fit a new bottom tensioner at the same time, and make sure the bottom chain guide isn't broken.
  5. Brian-Northampton

    Brian-Northampton Administrator

    Thanks Harvey,

    Time is just a guide, I'll take my time over the job certainly, just wondered if it'll take several weekends at my slow but steady (checking and check again) pace thats all.
    Nothing on my engine has had a regrind, it's all as from the factory. I'm the only one ever to have taken the cylinder head off - that's about as major as it's been. the car has been in my family since new, so I've got the history.
    I've bought a set of Big End std bearings so far, I'll look into the strainer gasket (got a conversion set somewhere, would it be in that?) and bottom tensioner/guide.

    All thoughts are very very welcome.

  6. sdibbers

    sdibbers Well-Known Member

    Sorry to jump on someone elses post. But I've been reading the manual about changing main shells. It mentions that you should not reuse the main abd big cap nuts when doing this, what do you reccomend for this?


  7. harveyp6

    harveyp6 Well-Known Member

    Mains caps are retained by bolts, not studs and nuts, and you'll probably find that most manuals suggest renewing the big end nuts, but it's just a matter of them covering themselves in case something happens. You could put a dab of Loctite on them if you were worried, but I never did, and never experienced any problems.
  8. harveyp6

    harveyp6 Well-Known Member

    You should be able to do it in a day, so give yourself a weekend and you should be fine. IIRC I used to charge about 4 hours labour plus the parts to renew ends and mains on a 2000/2200.

    It should be.
  9. richarduk

    richarduk Guest

    My engine has done 5k miles with the original bolts used in the rebuild. Did not occur to me to use new ones. I guess we'll know in 20 years how they have stood up or if the engine suffers a catastrophic failure. :)

    The only bolts I know of that must be replaced are on engines like the Ford CVH where 'stretch' bolts are used.
  10. DaveHerns

    DaveHerns New Member

    I would just add to use a good torque wrench
  11. Brian-Northampton

    Brian-Northampton Administrator

    Has anyone found a good source (and cheap) place to buy main bearings?

    I've had a quote from ClassicEnginesAndSpares.co.uk for £75 inc vat and P&P but was hoping for something a bit better than that.

    I know wadhams have them for £125, but they are an expensive supplier. They want £100 for big end bearings, I got mine for £25.

  12. The Rovering Member

    The Rovering Member Well-Known Member

    Rich Moon told me they have become very expensive though I did manage to buy 2 sets of standard size 2200 bearings for around £40 from ebay though 2 bearings are missing from one set. I wanted standard as I have a new crankshaft to go in which was also £40 from Steve Walker (complete with bronze bush) & new standard pistons/rings for £40 from him too, bargain. Over & undersized bearings for not-a-lot seem to crop up on fleabay now & again.
  13. Brian-Northampton

    Brian-Northampton Administrator

    Hi Gary,

    Yes, they do crop up now and again on eBay - which is how I got my AE big end bearings for £24. However, they never crop up when you need them do they?

    I've phoned around, and £75 (all in) seems to be a reasonable price. I bought them in the end from FW Thorntons in Shrewsbury (01743 357081) and they seemed to have plenty in stock, and the chap was very knowledgeable. I found them both through Google, and recommendation while phoning around.

    Still, at least one of my bearing sets was a bargain!

    I've emailed Ian Wilson for the tensioners/guides.

    Based on Harvey's knowledge, I'll do it in the next few weeks rather than wait until the Winter - I'd hate to tempt fate!!!

    I trust you'll all watch this space for my trials, swearing, cries for help, numpty questions or even watch the video of the victory dance (I AM KIDDING :wink: )

  14. j_radcliffe

    j_radcliffe Member

    The big end cap nuts are an oddball thread. The thread is I believe from memory 16 tpi, which is not a normal size for that diameter nut. When I did my piston rings I did buy new nuts. If you decide to use the old nuts take great car not to lose them, as they are not something that your local parts store would have. I even tried a place which specialises in british fasteners here in Lyons NY, but he could not help. I ended up buying some for Pierre in (London I believe).

    Now that I know that mains can be replaced with the motor in the car, I will do that over winter I think along with the bigends.

  15. Brian-Northampton

    Brian-Northampton Administrator

    Here's an interesting one.

    I know that there are two types of main bearings. Known as "early" and "late" (how original :wink: )

    The difference is in the centre main bearing which does not have an oil groove in the earlys.

    Now, My Workshop manual says that this change happened from Engines suffix G onwards. (page 74A and 93A)

    My Workshop manual was (as most of them are) printed in August 1967, with no mention of any reprints.

    My P6 is a 1971 2000 TC with an Engine number of 41541585F - suffix F suggests early bearings.

    How can a manual produced in 1967 know about engines from suffix G onwards when F was still in use in 1971 ???????

    Can it be that suffix's from SCs and TCs changed at different times, and if so, do they still mean the same thing in this case?

    Now I'm wondering if I've ordered the right bearings....... grrrr.

    Your help and thoughts, as always, much appreciated.

  16. Brian-Northampton

    Brian-Northampton Administrator

    I just wanted to add to this conundrum, the well know bit about the change to the 4 cyl head gasket. To quote from the workshop manual:

    Again a reference to suffix 'G'. I have a suffix 'F', and also have the cast boss on the cylinder block indicating a later - reduced height block.

    Which leads me to believe that the suffix 'G' being quoted in the workshop manual is related to SC cars only and TC cars have a different set of suffix letters meaning totally different things.

    Does anyone have any information on what the suffix letters denoted, and for what car derivative?? Perhaps James Taylor covered it in his book, if anyone has a copy??

    I'm getting very confused,
  17. sdibbers

    sdibbers Well-Known Member

    I've wondered about this too. I have a suffix B engine but also with the cast boss. :?
  18. j_radcliffe

    j_radcliffe Member

    Looking in my Parts manuals they list two different head gaskets for the SC model, 549698 up to suffix F, and 549983 for post suffix F. The TC parts book just lists 549983, the later type gasket, so that would imply that they only had the later type head gasket. There is only one listing for a cylinder block for the TC, that being 550269, which is listed in the SC parts book as the post suffix F block.

    Taylor's book does not yield any useful information about the suffix. However if you have a TC with an engine number starting 400, 401, or 405 then the block you have was originally an SC block. If your engine number starts 415 then it is TC 10:1 CR, and if it is 416 then it is 9:1. Mine is 10:1 with a 5 stamped over a 6!

  19. Brian-Northampton

    Brian-Northampton Administrator


    I'm reading the manuals to make sure I'm prepared.

    On page 91A of operation A2-5 "Pistons and Connecting Rod, Overhaul" on point number 10 it says:

    Is this a necessary test to perform? or only if a full overhaul has been done. Judging by what they are saying, it sounds like there will be a few thou difference between bearings and to juggle them around to get the best fit across the four!

    There is an almost identical statement on page 93A, Operation A2-6 "Crankshaft and main bearings, overhaul" regarding the mains.

    BTW bigmoose (Dave) who joined the forum last week telling us about his P6 in the "Diagnosing Noise in a 2000TC Engine" only lives about 40 minutes away and is coming round next Saturday (4th July) to give me a hand changing the bearings (two novices to check and double check are better than one!). That's another win for the forum bringing us all together! It would never happen otherwise!

    Many thanks,
  20. harveyp6

    harveyp6 Well-Known Member

    You could get the same result by using Plastiguage,it's just a running clearance, and if you had no problems before, I see no reasons why you should have them after changing the shells.If you were to check, and move the shells around you would just be optimising everything before you start up, once you've run it it will all alter anyway. Remember that you are working with a worn not a new or reground crank, so there will be more running clearance because of that. Just make sure that when all the new bearings are fitted and torqued up that the engine turns over nicely.

    Buy yourself some "Graphogen" to coat the bearing faces on both of the big end shells, and the lower mains. (Trying to put any on the upper mains as you slide them over is more trouble than it's worth.) If not all the shells have oil holes, remember to get the ones that do in the correct places.

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