Mud-club
Chat & Social => The Bar - General Chat => Topic started by: gtomo2 on August 30, 2006, 11:06:55
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My replacement head arrived yesturday and i have never changed one before. its the left bank as you look at the engine (n/s). so not a lot of stuff in the way. So if anybody not doing much over the weekend and fancys giving me a hand plaese. as i dont know what i am doing.. Its on a disco 1991 3.5 efi. i am on the road til friday so anybody wanting to help me give me ring on 07894 691369. Thanks. Oh will provide tea/coffee and chocloate bickys (may even push for jaffa cakes) :wink:
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What he meant to say was its the left bank as you look at the engine from the grille and that means the offside one, or otherwise known as drivers side ;) lol
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i'd help you as im only around the corner (as you know!) but i dont have a clue either :D
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I'd help, but I'm a bit busy this weekend.... and I don't know if I can put up the misses moaning again :wink:
Ian
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im only around the corner and i see heads changed and it dont look to hard but i bet it is
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If only I wasn't up to my kneck I'd say bring it over. It;s not too hard but make sure you follow the torquing up procedure. Use a good quality thread lock/lubricant on the bolts (not copper grease as soem numpty did on mine :shock: ). Don't mix up any pushrods, stick them through a bit of cardboard to keep them in order.
Use the composite gasket if you want reliability, it will lower compression though so is it a new or a recon head? you can check how much has been skimmed, on the front of that head is a square luh with a hole in the end, if it's close to the gasket surface than the outside edge it's been skimed by the difference in the 2 apparently. You want fairly even copmression on both sides of the engine.
you should change the valley gasket too.
Can't think of owt else but if you get truly in the [PooPoo] I'm not too far away, just busy as a badger for the next 2 weeks.
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I've done this job and it's not that bad if you take it steady and follow the manual - I'm no engineering genius that's for sure!
Be aware that some valley gaskets have a right and a wrong way round - get it wrong and it's water in the ol time. I'd use a composite valley gasket as well as composite head gasket.
Totally agree about keeping pushrods in cardboard to make sure they go back as they came out.
I managed to shear a rocker arm bolt but it drifted out easily enough. That was plain stupidity on my part because I was tired!
I'm sure you'll be fine. Everyone had to do this sort of job for the first time once!
Mike
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Thanks for the adivce i will take it in and got a full gasket set so will change the vally one as well. just need to buy a book on in now and pray the weather holds. its a second hand head dont think its been skimmed as it looks dirty around the cyl head valve area.
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Graeme i can sort you that disc its got all that info on it!
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If the head is second hand are you sure it's flat? I had my heads skimmed when I did this job as I didn't want to be doing it again in 2 months! Cost me 20 quid a head I think.
You can download the workshop manual for a V8 from a Polish site. Just google Land rover workshop manual V8 - it should work.
Mike
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Graeme i can sort you that disc its got all that info on it!
Thanks mate i may just need that yes please
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Ok mate pm me your address and you shall have it
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Had a good look at the head today with matty and his dad (and a big thanks for the use of the garage). and thought better of it will have to do the job correctly so will have to get the head skimmed first. so we fitted the new springs instead and after shearing a few bolts off and having to redo so mounts and ditch the rear anti roll bar its starting to look good (just still sounds like a tank :roll: ) But at least i did it in the dry and not outside. Only thing that went wrong i forgot to tighten the n/s/r wheel nuts back up and wondered what the knocking nosie was coming from the back thought oh great thats the propshaft gone. but no only loose nuts (story of my life :wink: ) so one quck nut tighten later and she is ok 8) .
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no problam mate if you need to know where the bloke is to skim the head let me know e can tell you were he is
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discos
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Why are you changing the head???
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the studs have broke and no fread in them
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Studs have broke... how much of the broken stud is still protruding from the head?? I.e. have they snapped flush with the head, or are they still protruding slightly?? If so how far, more or less than the exhuast manifold??
Ian
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well what i can see the back ones have come out and there is no fread in some of them but the overs not got a clue
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there are four studs missing two have stripped out the thread one is snapped half way inside the head and one is snappedd flush with the head.
But i dont have the kit to drill them out and re thread them plus got a new seconed hand head with the car.
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there are four studs missing two have stripped out the thread one is snapped half way inside the head and one is snappedd flush with the head.
But i dont have the kit to drill them out and re thread them plus got a new seconed hand head with the car.
Shame the two have snapped inside the head....
The striped ones could be re-drilled and helicoiled very easily, but the snapped two would be slightly harder.
If they'd snapped protruding from the head, then you can usually get them out by welding a bolt to the broken section... the heat of the welding usually helps them out.
You could probably drill the two snapped ones quite easily... would usually be easier than removing the head. The problem though is access... you need to make sure you drill straight - which is a bit awkward with the head still on the engine/in the car... at least if you want to make sure you do it properly.
Ian
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ian you prob got all the kit o do in though lol
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Shame the two have snapped inside the head....
The striped ones could be re-drilled and helicoiled very easily, but the snapped two would be slightly harder.
If they'd snapped protruding from the head, then you can usually get them out by welding a bolt to the broken section... the heat of the welding usually helps them out.
You could probably drill the two snapped ones quite easily... would usually be easier than removing the head. The problem though is access... you need to make sure you drill straight - which is a bit awkward with the head still on the engine/in the car... at least if you want to make sure you do it properly.
Ian
They are on the easy toget at side of the engine. but just never done it before plus not having the kit. plus like you say dam hard to drill stright when the head is at a angle. and alloy is so easy to drill through which would be my luck
:roll:
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and ou have bought the gasket set
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and thought better of it will have to do the job correctly so will have to get the head skimmed first
Sort of....
But do you know if the other head (the one your leaving on) has every been skimmed?? You could end up with a different compression ratio on each head, which isn't the best.
Or, has the new head you've got ever been skimmed?? Again, you could end up with the same problem, but in reverse.
IMHO, all I'd do is check the new head is flat - which you can do yourself with a flat edge and go from there. (as long as the face is in good condition)
If you want to do it properly, you need to take both current heads off and measure the piston/cylinder volumes, and then measure the volumes of all 3 of the heads... and calculate the Compression Ratio.
Ian
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this sounds like a garage job lol :D
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this sounds like a garage job lol :D
Wasn't it a garage that advised just to have the one head skimmed?? :wink: :roll:
Ian
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this sounds like a garage job lol :D
Wasn't it a garage that advised just to have the one head skimmed?? :wink: :roll:
Ian
Yes but he did point out to me the down fall of just getting the one head done and not knowin if the original head's had been skimmed before. or if the replacment had been skimmed as we had a good luck at ti but coukd not see if it had been skimmed before
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Yes but he did point out to me the down fall of just getting the one head done and not knowin if the original head's had been skimmed before. or if the replacment had been skimmed as we had a good luck at ti but coukd not see if it had been skimmed before
Sorry was just having a (joking) dig at Matt :wink: ...
I really wouldn't bother gettting the head skimmed, all I do is check it's flat, and then just presume that it's never been skimmed, and that the one on the engine at the moment is original - and hasn't been skimmed.
And just bolt it all togther.....
Or you could take some volume measurements..... but depends what your after.
Ian
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ian got that td5 built yet :D it will be fine
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My TD5 is still 'in the build' process....
It will be fine
... :roll:
Matt, what do you think the effects of a high compression ratio (i.e. you skim too much of the head) would be???
Ian
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if the head has not been skimed and it dont look like it has because when a head is skimed the edges are sharp but the head he has gont the eadges are not sharp so it might not of been skimed the only way to solve it it take both heads off
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if the head has not been skimed and it dont look like it has because when a head is skimed the edges are sharp but the head he has gont the eadges are not sharp so it might not of been skimed the only way to solve it it take both heads off
Depends if it's properly finished.....
I know of some one who used to sell recon engines.... They were freshly painted, so must have been rebuilt.
Not. All he did was repaint them, never stripped them down or rebuilt them.
Ian
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yer true so whats they way to do it then
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Properly...
Take both heads off, and meaure the volumes of the head and the cylinder/piston.
Do the calcs and compare the two results.
Ian
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and if on is bigger get the biggest one skimed
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and if on is bigger get the biggest one skimed
You'd skim the one with the lowest compression ratio (so both became even) which is actually the one that has the largest volume measurement.
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you can check how much has been skimmed, on the front of that head is a square lug with a hole in the end, if it's closer to the gasket surface than the outside edge it's been skimed by the difference in the 2 apparently. .
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you can check how much has been skimmed, on the front of that head is a square lug with a hole in the end, if it's closer to the gasket surface than the outside edge it's been skimed by the difference in the 2 apparently. .
Cant find that lug or more likly i just could not see it. :roll: will have to have a good look and feel of the head today and have a think about which route to take. weather to put the new head on or get the orignal one drilled out and re threaded
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It's a small square lug, obviously on the finished surface of the head, less than an inch square with a hole in the front (or rear) face. You should be able to see it in-situ on the driver's side head, though not get the callipers on it to measure.
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It's a small square lug, obviously on the finished surface of the head, less than an inch square with a hole in the front (or rear) face. You should be able to see it in-situ on the driver's side head, though not get the callipers on it to measure.
I doubt you'd really tell much if you can't measure it... even then you would need to be very accurate with the measuring.
What you could do is get the old head off...
Measure the volume, and meaure the volume of the new head...
If they are the same, just bolt the new head on... if different skim the new head to match. Unless the new head is already skimmed too far.
Ian
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I just knew this would not be a ten min job. Thanks everyone for the help so far. Sorry if sound thick just never done this sort of job before. changed heads on old cast blocks (talbot sunbeams etc). just not had any experance with alloy heads and dont fancy having to do it twice when i muck it up the first time. :wink: :roll:
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Do you need the Disco everyday???
The other option, is to keep your existing head.
If you can get the head off and over to me, I can get it repaired at work.
Means you can keep your existing head and not worry about CR problems etc etc.
Regards
Ian
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I'd be very tempted to take that offer up, provided you get the head off without it twisting then put it back as you found it. Trust me, if the first time you do the job it all goes relatively smoothly, you'll not think twice about tackling it again some time.
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What you could do is get the old head off...
Measure the volume, and measure the volume of the new head...
Ian
I think you need to explain how we would go about this though. One of the problems with measuring the combustion chamber in the head is that the head is often skimmed because it has warped, so it can be skimmed more at the ends than in the middle (they even get made this way) so whilst it's very accurate (provided you are dilegent in the measuring) because you can work out exact figures for each cylinder, the information alone isn't always enough.
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If you can get the head off and over to me, I can get it repaired at work.
Means you can keep your existing head and not worry about CR problems etc etc.
Regards
Ian
If you need a lift over with it mate just give a shout!
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If you can get the head off and over to me, I can get it repaired at work.
Means you can keep your existing head and not worry about CR problems etc etc.
Regards
Ian
If you need a lift over with it mate just give a shout!
Thanks for that just may be taking the head off and giving it to Ian as it may be safer than me drilling throught the head and out the other side. Will let everybody know over the weekend. it will depand on me geting the works van for a few days
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Just to add another spanner in the works...
This cylinder head…. been doing a bit more thinking – and I've probably just been a bit pedantic:
First off, a warped head will not directly affect the CR. All you are doing is measuring (with liquid) the volume of one (or more – see below) of the head chambers.
When you measure the CR, unless you're building a blue printed race spec affair, you'd only measure one head chamber and one piston/cylinder (so a warped head wouldn't show up)
Only if you wanted everything to be absolutely perfect you'd bother measuring every head camber and every cylinder –and then calculating the average.
Before you even started this though, you'd check that the head wasn't warped (well, more than an acceptable tolerance) by having it slightly skimmed, or just with a flat edge and a set of feeler gauges. And then, even if you did measure every head chamber, you'd still only be taking an average.
Though, if we are talking race spec engines, and thus you wanted every chamber to be the same you'd just do a bit of machining :wink: ... the main thing is that the head face it flat (well within tolerence)
If we take your engine to be completely standard and running standard CR then….
Then unless the new head is massively skimmed, or from some super low compression ratio engine, then you shouldn't really have any issues.
If your engine was brand new (and hadn't done 'x' amount of miles) then it would be worth checking, but in this application and usage if the CR differs between banks it really isn't going to make that much difference. Not when you consider loses that already affect a 'used' engine.
As mentioned before, you could just measure the height of the head itself… although not the most accurate method; it would give you a basic idea.
When the head is off (easier access) just measure it's height, and then measure (in the same place) on the new head. You do need to fairly accurate to do this though (well to get a reading that's even worth taking) – we are not talking cm and inches here!!
In saying that, I will still happily repair your current head... will even give it a wash and crack test if needed!!! :wink:
Ian