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would it be a bad thing to change the oil rail without changing the head gasket? the engine has been assembled and torqued down but has never been started

I thought the head bolts screwed into the oil rail?

john TF wrote:I thought the head bolts screwed into the oil rail?

Yes, that is why you fit a strengthened oil rail to maintain the head clamping load.
I would consider that there would be no problem in doing a straight swop as long as the head bolts are measured/replaced to ensure that they are not stretched.
Geoff F.

The head bolts are stretch bolts. nErgo they can not be re-used.

i was going to replace the bolts. but I have now decided that gaskets are cheap on the scale of things so ill replace the lot

Debs wrote:The head bolts are stretch bolts. nErgo they can not be re-used.

All bolts are stretch bolts!..they stretch within the elastic limit of the material they're made from to provide the necessary clamping force.

MGR give a check dimension to enable them to be checked to see if they have been 'overstretched'. If they are still within the check length then they will still be 'elastic' and they can be re-used.

I'm perfectly aware of what happens to a fastener when torque is applied TYVM.

While it is possible to measure the bolts to ascertain whether they are within (what is an extremely fine) tolerance, I would warrant that it is highly unlikely for the average home mechanic to have the means so to do.

Given that (the liklihood of getting it wrong), it would be false ecommomy to merely assume they could be re-used.

Hence my advice (as a professional engine builder) not to re-use.

I would agree if the head bolts are being removed the integratiy of the gasket has been compromised and will need replacing as the pressure would be released. I also would replace all the bolts as mentioned above just for sanity as I wouldn't have a way to test to within the tolerances.

Whatever you say.

TYVM? (Sorry I don't talk text or acronyms, I find English better)

TYVM is not an acronym, it is an abbreviation for Thank You Very Much.

Your snide reply does you no favours, it merely serves to make you appear a bit of a tit.

Sorry it came across wrong, I was accepting your superior engine building knowledge. (But I did rebuild my first car engine in 1968)

Abbreviations are a blight on the use of our language imho!

Oh and there's no need to get personal but I do like tits.

As the average jo-public parts buyer is very likely to buy off a certain supposedly auction site the chances of them actually getting inferior quality or even out of spec and too long bolts is very high the originals would unless seriously over heated still probably be better than a lot of new bolts on the market. Also the number of times the bolts have been undone and re-torqued must have soem bearing on their use and reuse ........................................... but then WDIK .

Debs wrote:TYVM is not an acronym, it is an abbreviation for Thank You Very Much.

Your snide reply does you no favours, it merely serves to make you appear a bit of a tit.

You're wrong on that one I'm afraid...TYVM is an acronym of Thank You Very Much...

"An acronym is an abbreviation formed from the initial components in a phrase or a word. Usually these components are individual letters or parts of words or names"

Sorry but that is not true despite what wikipedia might have to say.

Indeed the current misguided ideas about the word 'acronym' that are so prevelent across the interweb seem to be as a result of a (rather distateful) creeping Americanisation of the English language.

From the Oxford English Dictionary: Word formed from the initial letters (or initial group of letters) of other words.

Examples would be:

'WASP' White Anglo Saxon Protestan
'LIAR' London Institute of Academic Research
'CALL' Computer Assisted Languag Learning'
'RAPTOR' Reconaissance Airborne Pod for TORnado


TYVM is clearly not a word ergo it is clearly not an acronym. It is in fact an abreviation formed as an initialisation.

A subtle difference I agree, but a difference none the less.
`

Soooo.... getting back to the topic of the thread - can the oil rail be changed without disturbing the head gasket? Because the stretch bolts go through to the oil rail, you would inevitably have to "de-torque" the cylinder head in order to release the oil rail. Which I know isn't the same as lifting the head off, but one wonders whether it would be a false economy at that stage not to change the cylinder head gasket?

The up-rated fuel rail is part of an upgrade with the MLS head gasket - so it would seem sensible, if you've not done so already, to change the gasket to this type (assuming appropriate liner heights)

If you de-torque a head you will get some 'shuffle'. This shouldn't be a poblem on an MLS gasket (and by the way the Chinese N-Series is the one to use).

However, on an elastomeric gasket you run a risk of damaging the sealant tracks. Thus it would be false economy not to lift the head and replace the gasket.

Rob, as a new owner with a lot to understand, your comment "with the MLS head gasket . . . . change the gasket to this type (assuming appropriate liner heights)" ~ isn't this gasket suitable for all engines and if not why not please ? How, where & when does "appropriate liner heights" apply ?

The reason I ask is, my recently acquired car came off the production-line Dec '96 (registered '97) and was fitted with an MLS gasket, along with new oil-rail and stretch-bolts, about 4,000 miles ago by the previous owner ~ work carried out by a reputable firm and the job handled by an ex- MG mechanic . . . . . including head skimmed, some valves re-cut, pressure tested etc. I should add the car hadn't suffered HGF but the job was done by the PO as a precaution. Is there a reason I should doubt the gasket wasn't suitable ?

Thanks in anticipation.

Paul,

For the MLS gasket to work properly you need a liner 'stand proud' of 4 thou. If the liners do not stand proud then the MLS gasket will not seal properly and you would need to use the elastomeric gasket.

If the car has done 4000 miles and all is well, I wouldn't worry.

Hi Paul,

As Debs says, MLS (Multi-layer shim) gaskets depend on a small amount of stand-proud of the liner from the deck of the cylinder block (which should be around 2-4 thousandth of an inch, and shouldn't vary more than 2 thou from liner to liner). These parameters all need checking prior to fitting. Earlier K-series often left the factory with the liners flush with the deck height of the cylinder head - which was completely within tolerance the design specification, but not much use for fitting the MLS gasket. Engines with "level" liners are more reliable with the elastomeric Payen gasket (which has an upgraded design these days and therefore better now than the original).

I guess your question is more "have I bought myself a pile of trouble?" To which I think Debs' answer is quite right: suck it and see. Chances are it will be absolutely fine

further discussion on HGF on page 2 of this topic