XUD7 head gaskets

[nametooshort]

Good morning folks.

I think soon I will have some time to borrow my friend's car while they aint here, so that will give me a couple of weeks of not needing to use my 305 wagon as my daily driver. I am going to do a few things on it, and one of the things I wanted to do was the head gasket.

The reason is that this car is so damn useful, I would rather actually spend a scheduled week of maintenance, just as a precaution, rather then risk something serious going wrong when I actually need this car.

Its done about 170k miles, and I think its still got it's original head gasket. I know original factory XUD7 gaskets are said to pop reasonably consistently around 110-150k miles, so mine (assuming it's not been replaced already, which I think is the case) is well overdue to pop. It seems from what I gather so far, some head gaskets are better then others, and this 110-150k lifespan is only applicable to factory gaskets, whereas some modern replacements are much better?

Also I am getting a little oil seeping down the rear of the block, coming from the rear/timing belt end, but not from any of the oil seals, or the cam cover I think, so the only thing I can really think of is that it's seeping out of the block/head joint (which is after all not unheard of, right?).

So I was thinking of taking the head off, fly-cutting it until it's straight if it's bent, and fitting a decent gasket. I have a few questions:

1) Is it true that all headgaskets are not created equal, and some are much better then others? Like, original factory/ new-old-stock genuine PugCit gaskets from that period are inferior to more modern aftermarket gaskets? If so, which is the best gasket to get?

2) On XUD heads, are valves recessed enough to allow you to flycut the head without removing the valves? Or not? I know it's a bit of a redneck thing to do, but on some cylinder heads the valves, although in theory have to be removed for machining, can in fact be left in, since they sit deeper into the head then the head's mating surface, so their heads end up being like 0.5mm or more blow deck, which means skimming 0.1mm is perfectly OK with valves left in. Then again on some engines this is not the case. Anybody knows if it has whirl chamber inserts, and if so, how hard are they? My friends flycutting machine is old and don't like hard metals, its ok with aluminum and juuust about OK with iron, but if it hits hardened inserts it has a session and usually throws it's head. I have to use a big milling bit to machine heads with crap quality castings (with hard patches) or with very hard inserts.

3) Do I guess correctly, that after 25 yrs and 170k miles, it WILL need machining, no point even wondering about that.

4) Do I really have to remove the head before I know what gasket I need? I know the 'official' way is to take the head off, measure protrusion, and then pick the correct gasket. But, in practice, is that really necessary? Somebody mentioned that this process is over-complicated, and a lot of brands just sell 'one size fits all' gaskets, but then somebody else said this is very important to do correctly. Who was correct? How do I pick which gasket to buy, and can I buy one BEFORE taking everything apart?

5) Is there anything I am likely to need apart from a head gasket kit? I already changed the cam belt like less then 200 miles ago.

Thanks!

[spider]

I have to run off so I will be brief and just answer a couple of questions:

I went to the expense of a genuine one for my 205TD (that was a 1.7, well 1.8 but tis an XUD7T) , partly as I did it on the street and I did not want to do it again with people constantly asking me what I was doing etc etc. It was still fine about 70 odd thousand miles after when I sold it too.

It should be straight unless its been cooked. You could just change the gasket and chance it but if it goes again then that's the chance you take. A straight edge may help determine if its truly flat or not.

You can see the notches to determine the thickness before you take anything apart. Although it might be considered bad practise I've always fitted the thickest one available, no one had ever complained.

Apart from major disaster they do tend to fail quite slowly though rather than all of a sudden...

[citronut]

i think it depends on how the engine is looked after to how long the gasket will last, and if the car has been used without the cooling fans working any time in its life,

i always use Elring, Payen or Melior and the thickest of these brands,

as Andy says you can see the notches on the original gasket in situe at the gear box end of the head,

some people say to use the solid metal gasket, of which i have no knowledge of/never tried,

you should NOT fly cut these heads unless you intend to remove the ricaros/inserts,

the reason being the fly cutting wheel will pick steel swarf which will tear/scor he aly head face,

i belive even milling there is a special cutting bit for cutting mixed metal surface's like these heads,

also its best to have the head skimed even if it only requires just a very light go over,

but the more you have off the more likely you will need to sink the valves into the head/there seats,
as there depth is critical otherwise they contact the pistons,

so the least you have skimed the less work you need to do to the valve, then also the less time involved re/shimming the valve clearances,

regards malcolm

[CitroJim]

I'd very much agree with the foregoing. The BoL gives a good account of sizing head gaskets by measuring piston protrusion with a DTI but generally if you use the thickest you'll be fine. It may lower the compression ratio a smidgin but that will be of no consequence on an NA engine...

By 'Ricardos' Malcolm means the pre-chambers. These are called Ricardos on account of their design. they're Ricardo Comets...

Definitely have a light 'clean up' skim.

[nametooshort]

Thanks for all the info. I still don't understand a few things tho.

From various things I picked up from talking to people, I was under the impression that there were two 'types' of head gasket:

-The original style gasket, as made by PugCit at the time when there engines were made, and copied by various aftermaket/cheepy pattern part manufacturers.

-The 'other' style, which was made later as a revision of the original (not a copy) by some aftermarket manufacturer, and has since been copied by some other pattern manufacturers.

The 'other' style apparently being vastly superior to the PugCit gasket, because the PugCit (and copies) style gasket has a finite lifespan, and will pop at 110-150k miles, EVEN if it's looked after and not abused, because of some design miscalculation or something. Like, its not a case of 'it will pop if overheats' or something, but a case of 'it will pop just because its a bad design'. Whereas the 'other' style gasket does not pop on it's own for no reason.

This is just what I seemed to notice people talking about, I have no idea whether this is true or not (which is what I am hoping you guys can tell me).

So is the usual practice to press the pre-chambers out and then mill the head and then press them back in, or can you just be lazy and using the aforementioned special mixed-metal milling bit, just mill it as it is?

About the valves. Does anybody know (at least approximately) how much you can skim (assuming you are starting with a stock head, and using the biggest gasket available) without touching the valves at all?