Extra thick head gasket for Mondeo Ecoboost?

[kerplunk]

I had the cylinder head for my Mondeo Ecoboost 2.0l turbo engine skimmed today and the engineer said he had to take off 24 thou/0.6mm to get it flat which seems quite a lot. So I've been looking at extra thick head gaskets to avoid problems with valve to piston clearance and raised compression.

The standard gasket is 1.25mm thick so I'd be looking at one around 1.8mm. Sounds simple enough but I'm wondering what the downsides are if any? Is it going to be more likely to blow? Do I need to torque the head down more? So far I've only found one manufacturer - Cometic - who appear to make them in loads of different thicknesses. I've heard of Cometic but no idea how well they're regarded. Should I be looking for a replacement head instead?

Edited by kerplunk on Wednesday 10th October 21:20

[kerplunk]

stevieturbo said:

Cometic are fine.

What are manufacturers instructions regarding head gasket thickness after head machining like that ?

Do you mean Ford? I enquired at a Ford dealer, who enquired to Ford, if there was a service limit on skimming these heads - they sent back an engine spec sheet which had only one possibly relevent bit:

Cylinder Head
Maximum mating face distortion (crosswise) - 0.1mm

But I don't know how to interpret that.

Edited by kerplunk on Wednesday 10th October 21:22

[kerplunk]

Sardonicus said:

Are you sure Ford dont offer a selection of head gasket thickness's to allow for differing piston protrusion across production runs and in service head machining etc ? like as been the way with diesel engines for years not familiar with working on this engine so am only surmising

I've no idea I'll have to ask. Someone at a company who do performance stuff for Focus STs (same engine) told me it was 1.25mm standard and that seems to be borne out by looking at suppliers of head gaskets who list my engine.

[kerplunk]

Thanks for the face-slap Mignon - this is what I came here for because whilst a rank amateur like me trying to limit my losses might HOPE things are simple I'm at least savvy enough to know that's often not the case and getting good advice is imperative if I'm to avoid throwing good money after bad (and that's the absolute imperative here).

I've had a lot to learn - when the recovery truck delivered the car to my house the first thing I did was take the plastic engine cover off and that was the first time I'd laid eyes on my engine since I bought the thing nearly 5 years ago. Over the last 5 weeks I've taken the head off to assess the damage (1 x piston chipped and a scored bore, and coolant in the other 3 cylinders) and the weekend before last I took the block out. My roadmap going foward was to get the head sorted first (in case there's anything wrong with it!) and then either go for new pistons and rebore, or buy a new short block from Ford (my favoured option). And that brings me to this point.

So anyway - calculating head gasket thickness seems like an interesting new thing to learn about but is there any point if the top of the head is bent by 0.6?

Is it not fubar? (I think I know the answer to that already)

Edited by kerplunk on Thursday 11th October 10:34

Edited by kerplunk on Thursday 11th October 11:36

[kerplunk]

Penelope Stopit said:

Mignon said:

stevieturbo said:

Can't say I've ever heard of anyone trying to straighten a head, so not sure if that comment is in jest or not ?

Think about it. What causes a head to warp? I'm not talking about just the obvious but at a molecular level what is a "warp" in a piece of metal? In which fields of metalwork do we encounter such things, what is done about it and what is the technical term for that?

30 years ago when faced with a really badly warped head (20 thou or so) I worked all this out from first principles and then rather than machine the head true I straightened it first and then skimmed the last thou or two off to get a perfect gasket surface. It has been an invaluable thought exercise in redeeming heads that might otherwise have been past using again.

Great information once again here, I have recently been wondering what the outcome of skimming and re-using a head would be due to the warp still being there

The penny drops!

[kerplunk]

227bhp said:

Mignon said:

Think about it. What causes a head to warp? I'm not talking about just the obvious but at a molecular level what is a "warp" in a piece of metal? In which fields of metalwork do we encounter such things, what is done about it and what is the technical term for that?

30 years ago when faced with a really badly warped head (20 thou or so) I worked all this out from first principles and then rather than machine the head true I straightened it first and then skimmed the last thou or two off to get a perfect gasket surface. It has been an invaluable thought exercise in redeeming heads that might otherwise have been past using again.

Unequal application of heat, but how are you going to replicate that in the opposite?
Off the top of my head (duh) all I can think of initially is putting it in a bloody huge press or attempting to apply heat to certain areas of it to get it to pull back the other way, but neither seem easily viable.

Surely you just apply pressure and stick it in a microwave oven (only kidding about the microwave)

[kerplunk]

Mignon> It's academic now but I'm curious how much straightening a badly warped cylinder head would cost ball park and who does it?

(You never know - a cylinder head may come my way)

[kerplunk]

Mignon said:

kerplunk said:

Mignon> It's academic now but I'm curious how much straightening a badly warped cylinder head would cost ball park

Nil. Ball park. Could run you as high as 10p for electric.

kerplunk said:

and who does it?

You do.

Feck, now that's annoying - I wouldn't even have had to pay for a hair-do (not that she's bold or anything - we just don't co-habit)

[kerplunk]

Mignon said:

kerplunk said:

Feck, now that's annoying - I wouldn't even have had to pay for a hair-do (not that she's bold or anything - we just don't co-habit)

Well you can still do it and then get the head skimmed a second time because the gasket face will then be convex instead of concave as it was. That way you'll end up with cams that aren't bent in their journals, valves that actually still seat on their inserts and all 4 combustion chambers the same size instead of 2 small ones at the ends and two big ones in the middle. Then it actually will have had 0.6 mm skimmed off it and you will really need a 0.6 mm thicker gasket which you don't at the moment. I'm still waiting for you to work out what gasket you do need as it stands. It's pretty basic trigonometry.

No you've got me. I've thought about it but given what you've pointed out about the combustion chambers I can only conclude that no gasket of any size could put it right without having different compression and piston to valve clearance on the outer cylinders to the innner 2. So unless it's a trick question I'm beat.

I may give your suggestion a go (thanks for that - there's still hope!) but I've been pricing up a remanufactured complete engine today and finding the gap between that and the short block + refurbed head option not as large as I thought - I'm tempted, but I need to think about it.

[kerplunk]

Mignon said:

kerplunk said:

No you've got me. I've thought about it but given what you've pointed out about the combustion chambers I can only conclude that no gasket of any size could put it right without having different compression and piston to valve clearance on the outer cylinders to the innner 2. So unless it's a trick question I'm beat.

No that's all true but there's the best compromise gasket thickness which involves working out what has actually happened to the chamber volumes, or alternatively how much has been skimmed off each part of the head. That will never be anywhere close to the maximum amount which got skimmed off just the very ends of the head.

0.3? Yes I just split the difference, sorry. My mind's been on other calculations (costs) the results of which mean I'm now inclined to give your suggestion to straighten the head and skim it again a try (unless a 2nd-hand engine comes up, but they're like hen's teeth).

[kerplunk]

Mignon said:

kerplunk said:

0.3? Yes I just split the difference, sorry.

You're probably not far off with your random guess. I'll write a technical article on it if I can muster the enthusiasm. In the meantime I suggest you lay the cams in their journals and see how much they rock. Push one end down and use feeler gauges to measure the gap at the other end. Then do the oven trick and see what happens and let us know.

Thanks, I'd already decided I was going to measure it (this time!) but I hadn't thought of using the cams.

[kerplunk]

kerplunk said:

Mignon said:

kerplunk said:

0.3? Yes I just split the difference, sorry.

You're probably not far off with your random guess. I'll write a technical article on it if I can muster the enthusiasm. In the meantime I suggest you lay the cams in their journals and see how much they rock. Push one end down and use feeler gauges to measure the gap at the other end. Then do the oven trick and see what happens and let us know.

Thanks, I'd already decided I was going to measure it (this time!) but I hadn't thought of using the cams.

A valve spring compressor has been sorted so might happen this weekend. If it'll fit in my oven that is - there's a small pivot rod for one of the timing chain sliders that protrudes 15mm on one side that may spoil the party - I've tugged at it a bit but seems pretty solid. Might go in at an angle but I need to test that.

Any instructions for how to sit it in the oven?

Do I need a flat surface for it to sit on?

Upside down perhaps (there's dowels in the top though)?

Turn it over half way through maybe? (that's a joke)

[kerplunk]

oh by the way - a correction. I picked up the head from the machine shop yesterday and the amount taken off in the skim was 28 thou, not 24 as I previously stated.

[kerplunk]

It fits!



And we're off...

[kerplunk]

The oven's been off for 4 hours now and it's still too hot to touch. Obviously I'm very keen to measure the effect but I guess it'll be tomorrow now.

[kerplunk]

Just did a quick test using the camshafts. First impression is that nothing has happened - the exhaust camshaft still has an obvious rock to it when you press on the ends - feels the same as it did before the oven treatment to me (the inlet camshaft had no movement beforehand and still doesn't)

[kerplunk]

Mignon said:

Overheated cylinder heads don't just bend uniformly like they were put in a press. The heat comes from the combustion chambers and the bottom of the head tends to distort more than the top. The head changes overall shape more than it bends. If you had a camshaft that was still true in its bearings then by definition the top didn't distort much. Put a straight edge across the gasket face and see what that looks like now.

It's consistent with what the engineer who did the skim said - the warp was deepest on the exhaust side.

Could the fact the exhaust side was facing the oven door have made a difference to the temperature do you think? I did it that way because of the protruding pivot rod but I might be able to get it in the other way around with a bit of shoving, and give it another go?

[kerplunk]

227bhp said:

It's because you didn't baste it
Seriously though, how did you measure the temp?

I used to have cheap probe connected to a digital read out for doing stuff like that, put probe in oven, read out on worktop, thin connecting 'cable' was simply trapped in the door.

I didn't measure the temp - I turned the knob to midway between the 200 & 220 marks. I'll pick up a thermometer today and have a pizza for me tea (after I've given the oven a good clean).

[kerplunk]

I should also have a decent straight edge for measuring the gasket face later too, I've been looking at it with an ordinary steel ruler and the result is inconclusive so I shan't say anything yet.

[kerplunk]

Ok so the gasket face is flat as a flat thing - can't get a rizla in anywhere.

So that's that, but now the oven temperature - I bought a multi-meter with a temp probe today ( here) and it appears that, despite erring on the high side, the oven probably still wasn't heating the cylinder head up to 200C. What I found was that with the oven temperature knob in the same position as the Sunday roasting, the temperature constantly varied +/-5C-ish as the halogen clicked on and off and only hit 200-202C at the peak before sinking back to 190-192C at the low point, so my best guess is the head never got higher than 195-ish.

So unless someone tells me it's a bad idea I plan to have another go tomorrow.

ps. the pizza was fine.

Edited by kerplunk on Tuesday 23 October 23:12