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I'm intending to change the head gasket on my 1989 Fiesta 1.1 (OHV) this weekend - the most complicated job i've done so far, so i'm a bit nervous! I was under the impression that the head bolts should be changed whenever their removed, since they stretch as they are torqued up. However, reading the Haynes manual there's no mention of changing them - should I or not? Also, is it worth doing anything else, like changing the valve stem oil seals, whilst the head is off? And finally, is it possible to tell if the head needs skimming without any special measuring tools? Cheers for any help!
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owen
One of the easiest engines to start on if you've not done the job before.
The head bolts on this engine do not need replacing - it's an older design and does not use stretch bolts.
Unless you've done a compression check and are convinced the valves are Ok, while the head's off it's worth grinding the valves in and replacing the valve stem oil seals. I assume it's done a fair mileage, and I've found on these restoring the compression with a valve grind works wonders.
The question is why are you changing the gasket? I assume you've reason to believe the head's warped. It may be possible to check the head using a straight edge and feeler gauges, but it isn't easy. These cast iron heads are less prone to warping than alloy heads, but if it's been really 'cooked' it may be. For a minimum cost job on an old car you may get away with a gasket replacement alone, but it can't be guaranteeed, and you may be taking the head off again to get the head skimmed.
If you're going to take the valves out, probably worth getting it checked at a machine shop and skimmed if necessary. It can't be done on an assembled head.
Regards
John S
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Cheers for your help John - the reason for the gasket change is loads of mayonnaise in the rocker cover when I serviced it a couple of weeks ago, and the coolant level going down. I don't think it's too bad, as the performance is still reasonable (i'm not sure how reasonable - my other car's a lotus elan, so comparisons are difficult!). I've also done a compression test - can't remember the figures, but one cylinder is only about 60% of the other 3. So, on this basis, i reckon it's only a slight leak which should be cured by a new gasket alone. However, if on the basis of this info you reckon that i'd be as best to grind the valves in as well, then i probably will, as i don't intend to have the head off twice. The car's only done 74k but it's worth about 50p, so i don't want to spend a fortune on it, but if it'll run ok for another year or two i'll be happy.
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Owen,
If only one cylinder is down on pressure then it is unlikely to be the head gasket that is the problem. The two possibles are either that the piston ring has gone, or the valve seals are leaking. An easy test to try is to put a teaspoon of oil into the cylinder that is down on compression (through the spark plug hole) and test it again. If the compression returns to normal, then the piston ring is leaking. If the compression doesn't improve then the valve seals are leaking.
Hope this helps
Nick
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Owen. The Valencia OHV engine is *very* suceptible to condensation.
Losing a bit of water isn't a major problem - maybe you have a leaking cooling system?
I reckon you'ld be suffering major overheating problems if you had a gasket leak.
If it runs ok with one piston at lowish compression I would just leave it and run it 'till it physically stops which might be a very long while away.
If you do do the gasket I worked on a 1.3 OHV engine and it was a doddle. Make sure you check the head for cracks - often round the valve seats.
It sound like an oldish car. Don't do too much work on it.
--
These are my own opinions, and not necessarily those of all Toads.
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owen
Nick C is right. Unless there's a major gasket leak, it won't show on a compression test, and that 'low' cylinder probably has burned out valves, so I'd certainly grind the valves in when the head is off.
Equally, toad is right to say these engines are prone to condensation, but if the water loss and condensation are a new phenomenon, given how easy and cheap is is to do a 'head job' I'd give it a go, despite the age of the car. It is likely to make it run much better.
Regards
John S
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If I remember correctly it is very unusual for head gaskets to fail on the ohv 1.1. It is based on a very old design of engine where I beleive every thing is made of cast iron, so you dont quite get the same "battery" effect that you get with cast iron block/alloy heads. It can rust internally eventually though. Also there are very thick walls between bits, ie the water jacket holes in the head are miles away from the bores etc...
Coolant leak - check the heater matrix - these do fail - especially in winter!
Mayonaise - Has it just been used for short runs? These old engines were always prone to this as not a lot happens mechanically at the top of the engine.
If you do remove the head be sure to keep the push rods in the same order (push into a length of cardboard) and be very careful when replacing the rocker shaft, make sure the push rods are correctly seated. Also ensure there is oil in the pushrod cups as it can take a while to splash into these on first restart.
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Needless to say you will tighten the nuts in the correct sequence. Use a torque wrench if you can, but on old-fashioned engines you can gat away with just a good heave on a standard length spanner or lever.
It is always very important to re-chech the tightness after a few hundred miles running, as head gaskets flatten slightly in use, and you can end up with loose bolts and a new leak. It is tedious I know if you have to dismantle things just to get at the bolts.
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