Viewing 31 posts - 1 through 31 (of 31 total)
  • Engine rebuilding (yet more amateur mechanic content)
  • molgrips
    Free Member

    How difficult is it to say change piston rings once you've got the engine out? What else would one do if one was dismantling the engine? Big end bearings? Crankshaft bearings? Valve re-seating?

    sobriety
    Free Member

    If i was doing it, after the hassle of getting the engine out, i'd be wanting to change/upgrade as much as i could physically afford!

    molgrips
    Free Member

    So what would be on your list then?

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    andylaightscat
    Free Member

    what engine is it?

    molgrips
    Free Member

    VW 1.9 TD (AAZ engine code). I don't think the compression is particularly bad, I just fancy opening up an engine and restoring it at least once in my life. Next second car we get probably won't be a junker, so this might be my last chance 🙂

    (go on, call me stupid and tell me it's a waste of time)

    thisisnotaspoon
    Free Member

    your stupid and its a waste of time

    what needs doing, if it still works I'd leave it be untill it won't start.

    molgrips
    Free Member

    if it still works I'd leave it be untill it won't start

    Thanks for that. However I personally am still somewhat interested in dismantling my engine. You don't need to know why..!

    timraven
    Full Member

    If you replace the rings even with the same size you'll need to de-glaze the bores, not difficult but you'll need tools. Replace any bearings and seals you can find. Regrind head and reseat valves.
    Clean everything meticulously then clean it again as you put it back.
    If you really want to go to town balance and match the manifolds to improve air flow (power)

    Brainflex
    Full Member

    If your gonna rering it you need to do the mains and big end bearings. Get the valve seats recut. Obviously new timing gear and waterpump and your done. Fit a new clutch when you put it back in.

    TandemJeremy
    Free Member

    I have only done motorcycle engines. I would say there is little point in changing piston rings – if things are worn enough to need new rings a rebore is probably in order.

    Bottom end bearings are really a specialist job to do assuming they are shell bearings – need a regrind of the crank and very accurate measuring

    Valve grinding is fine for the amateur to do.

    If you really fancy rebuilding and engine I would get an old small 4 stroke motorcycle engine and do that. CG 125 – something like that

    coffeeking
    Free Member

    Yeah it depends how easy it is to get it out. On my first car I could strip it down to its bear essentials in about 3 hours, so I'd do only a few bits and pieces until the next thing died. With one of my currect cars its an 8 hour job (12 if you ask toyota) just to get the engine out of the bay before you start work!

    Rings- delicate job but with the right tools not too bad. I'd be doing bearings and seals as tim says, and probably for perfection I'd re-seat the valves, re-adjust them, port and polish the manifolds (not as easy as just taking a grinder to bits that look wrong, read up on it first anywhere but the internet). Of course you'd want to hone the bores for new rings, and possibly skim the head if it's in need. Always nice to flush out the coolant and oil ways. Personally if I had my engine out again it'd be stripped down to individual pieces, cleaned and degreased and i'd do some more fun stuff like powdercoating/ceramic coating the block.

    Just depends how far you want to go. And I disagree with TJ on this one, bottom end bearings are fine for an amateur with knowledge of what to look for, and modern-ish engines will wear rings WAY before the bores, thats how they're designed, but boring it out to the next standard size up is not too pricey anyway if you find it needs doing.

    Milkie
    Free Member

    Sell it, get a proper engine. Petrol V-Power 😀

    Skankin_giant
    Free Member

    your better off starting on something simple, A series engines are pretty straghty forward, push rods are so much nicer to work with 😀 , or start on something like a old lawn mower engine (4 stroke one would be good) so you got a basic idea on whats going on, you can pick one of the up for a £10

    molgrips
    Free Member

    I'd rather do it on an engine I actually use so I actually get some benefit from my efforts.

    Don't piston rings need to be matched to pistons then?

    As for porting and polishing, I thought that was a specialist job.. What's involved? Is it literally just polishing the surfaces that the air flows over with a dremel or something?

    What about balancing? If the gubbins are all out could I take it somewhere and get it balance, then do the known governer mods to release more rpm?

    therevokid
    Free Member

    Rings aren't matched to pistons unless your refitting the old ones
    then you would make sure rings went back on the same pistons.

    I wouldn't worry about balancing – it's a diesel right ? the peak
    rpm's aren't really high enough to feel the benefit. (mine's a TDI btw).

    Given the fuel pressures and torque figures for diesel cylinder heads
    I'd leave it alone (personal choice though !)

    Milkie
    Free Member

    As skankin says, you need to understand the basics, and an A-series engine is very easy, although if its in a mini its a pain because you need minute hands to reach around things.

    I taught myself on a mini, using this book.

    Very good book for the A-series engine, explains everything, and I mean everything!

    If it was me, I wouldn't touch an engine, that I would actually use/rely on, unless I had sucessfully dismanteled another engine and got that back up and running.

    timraven
    Full Member

    You can replace rings easily, no they don't need to be matched to pistons. You will need to check bore wear as TJ says, but new rings will improve things if there is minor wear. To replace ends is also easy but if the crank is worn it's a specialist job as is the head regrind. You will need micrometers to measure the wear and an accurate manual to give you the tolerances. After that the risk is yours to take and as long as you're in no hurry then give it a go.
    Nothing like the first time an engine you've built runs 🙂

    If you're near Bath, I'll happily give advice. I was in the trade for 27 yrs, own business for 10.

    takisawa2
    Full Member

    You'll be fetching the head off obviously. Your not going to be doing much with it still on. Pop the sump off & take a pressure washer to it & the pick up pipe & oil strainer. I'd leave the crank in though, unless your going to get the journals re-ground. Usually if the crank is coming out you'd be taking the opportunity to get a re-bore. You should be able to do the crankshaft oil seals with it in place also. Pop off the big end shells & take the pistons out. There used to be a company called Cords who did piston rings for putting back in older engines, but we're talking 20yrs ago now, when I was tinkering with Ford Pinto engines in my Capri. New big end shells. As regards the bores there used to be a tool called a Glazebuster, basically a big flap wheel for mounting in a drill to de-glaze bores. Not sure if they are still available. Most of your work will be cleaning & scraping off gasket surfaces. Give the head a good de-coke & re-grind the valves. Basically changing any gaskets & oil seals you come across. Not sure about VW TDi engines but a skimmed head might be needed. Remember things like big end bolts etc might need replacing as a matter of course.
    Your biggest hassle…handling the engine while you do all this. A garage floor is not a nice place to be for hours on end. Plenty of bags & labels for recording which pot valves etc came from is useful.

    BoardinBob
    Full Member

    For polishing the ports, you don't want a mirror polish. The surfaces still need to be rough enough to create turbulence in the air flow.

    coffeeking
    Free Member

    Of course a D is different to an A series or a petrol lawnmower so IMO that'd be a bit of a waste of time, and since this is a car you dont rely on my personal thought would be "dive in" carefully and in a mechanically sympathetic way. Take digi photos of everything you do, the locations of parts, and put your bolts either in bags or (my preference) cut a piece of card to the shape of the face the bolts/nuts came from and put holes in it in the right places, pop the bolts through and tape them down.

    Buy a decent torque wrench.
    Buy a decent set of spanners (ring and open ended)
    Buy a decent set of sockets (6 sided, not "spline" type if you can, this REALLY helps with not rounding old nuts/bolts)
    Along with the tools mentioned above for measurement and fit adjustment.

    therevokid has a point, porting and polishing wont make much difference to a low reving TD, but I found it theraputic at the end of the job 🙂

    Be prepared to break things. And ultimately – dont be cheap! It took me the best part of a weekend to take the engine out and change the clutch, gearbox and cam belt of this:

    And when I put it all back together, spent another weekend cleaning the bay, replacing little bits etc and re-assembling I found the water pump was leaking and needed replacing – another major job that would have been so much easier if I'd done it while it was out 🙁

    molgrips
    Free Member

    the peak rpm's aren't really high enough to feel the benefit.

    Not unless you do the governer mod 🙂 The engine will pull up to 6krpm apparently, according to the weirdos who do these things to these engines.

    I appreciate the benefit of practising first, but I'm not gonna go out and buy a car I don't want, strip the engine, then sell it again.. Once I've had any engine apart I probably won't want to do it again 🙂

    I'm in Cardiff timraven – there's a place here that works on engine bits I can go to for head grinds etc.

    unless your refitting the old ones then you would make sure rings went back on the same pistons.

    Does that mean that you need new pistons and rings at the same time? That would make more sense.

    BoardinBob
    Full Member

    Out of curiousity, how many miles has the engine covered?

    mrmichaelwright
    Free Member

    i dread to think how little torque a PD engine outputs at 6K rpm 😆

    coffeeking
    Free Member

    mol – if you're getting new pistons you should fit new rings (out of sense, more than anything). If you're not replacing the pistons, new rings will go on the old pistons fine. The point is the rings bed to the bore, you just dont want them swapping between cyls thats all. Always note which cyl parts came from, and the orientation, before re-assembling. Usually the crank and rods were balanced together, sometimes (like mine above) the crank, rods and pistons were matched and dynamically balanced at the factory.

    hora
    Free Member

    Good luck molgrips. I personally admire tinkerers. How else are you supposed to learn? I reckon belts- cambelt change.

    molgrips
    Free Member

    handling the engine while you do all this

    I was thinking of buying or hiring an engine stand and putting the bits on my bench…

    Out of curiousity, how many miles has the engine covered?

    180k

    i dread to think how little torque a PD engine outputs at 6K rpm

    It's a TD not a PD – the old indirect injection engine which is fully mechanical and apparently very good for working on/modding according to the hardcore following online. It's also subtly different to drive than a modern D – more free revving, a bit more like a petrol, and it doesn't have a hardcore diesel clatter noise either.

    Not sure if I'll do it but I do rather want to change the gearbox which is possible in the car but I might like to go the whole hog just for the hell of it.

    Why do bores need de-glazing?

    Thanks for the encouragement anyway. I've faffed with the car so much that I feel a bit attached to it in a kind of begrudging fatherly way.

    mrmichaelwright
    Free Member

    ah, reading back i see it is indeed not a PD

    i stand corrected

    squeeze a 2.0TDI 140PS (or even 170) into it, lovely engine and you'll have a proper wolf in sheeps clothing 8)

    Skankin_giant
    Free Member

    Yes a A series or lawn mower would be diffrent but all engines have pistons valves etc, well accept Wankals and 2 strokes, but skill will be gained from taking apart anything and restoring it,
    but if your confident enough to jump straight in go for it, i found boxes for each part works well, and photos are good

    molgrips
    Free Member

    squeeze a 2.0TDI 140PS (or even 170) into it

    No need – the 1.9 AAZ is good for 230bhp which, when in an early 80s rabbit (aka mk1 golf) in the US where they think anything small is rubbish, really is a wolf in sheep's clothing when it does 0-60 in under 7 seconds.

    coffeeking
    Free Member

    Why do bores need de-glazing?

    Over time your rings wear a fixed pattern into the bore, and vice versa. It becomes nicely polished and a lovely close fit, and arguably the oil no-longer remains there as easily as it should – it gets scraped off too easily. With new rings you need to either get those rings to bed into the old shape of the bore (takes a long time, if at it happens at all, can cause problems) or you hone the cyl to get the two to wear together rapidly, giving a better seal and more power.

    Now open the can of worms that is "do I bed the rings/bearings carefully or do I rag the engine to seat them properly"….. Either way you'll want to change your oil up to a couple of times in the first 1k miles, so put in the cheapest correct grade dino oil you can find.

    molgrips
    Free Member

    I should've done this when the engine was running on veggie oil – that would have been intersting.

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