Contour Enthusiasts Group Archives Forums Modifications Zetec Maintenance Contour/Mondeo Zetec engines different?

About the PM, I still have several PM's I've sent that are unread when I know they have read and replied, no names here(cough..Bnoon,cough cough). Just the way it goes, Terry is usually pretty busy coming up with great new gadgets for us contour owners so we can't complain. About the head swap, I am almost POSITIVE it will be the cure to your power woes, just make sure you do a thorough inspection of all components and for God sake use new Head bolts!!

Terry is usually quick to respond to the PMs I have sent to him.

Work in progress - results to be advised.

Some interruptions for holiday aside, we're in the middle of swapping the heads.

It was unexpected to find that the Contour and Mondeo pistons are quite different:
The Contour engine piston tops have machined cut outs for the valves – 2 “D” shaped ones for the exhaust valves and one angled trough for the 2 inlet valves. And the centre of the piston heads is raised so that, at top dead centre, it's about 2mm above the top of the block. The Mondeo ones are completely flat and are very slightly above (too small to measure) level with the top of the block at TDC.

On the basis that we're doing this change because the heads are different, I have to say that the heads do look remarkably similar side by side on the bench. I haven't facilities for detailed measurement but the only notable visual difference is in the inlet valves: Mondeo inlet valves faces (the part you see looking at the valve from the piston) are flat with a small aprox 10mm diameter concave zone in the centre; Contour ones are concave over almost the complete area of the face. The exhaust valves of both engines are the same and similar style to the Mondeo inlet valves.

Whether this is of any significance I don't know. Does it suggest that the compression ratio difference is due to the pistons being different?
Any contributions gratefully received.

Assuming that the Euro spec Zetec is a higher comp. ratio (which I am absolutley positive it is) it seems like the US spec pistons would actually raise the ratio since the bowl is so much higher than the Euro spec pistons. When looking at the heads look at the surface of the combustion chamber bowls around the valves do the Euro spec valves seem to be seated deeper in the head(ie abit more shrouded)?

All I can think re the piston head design is that perhaps the raised section in the middle of the piston kind of compensates the volume of the divets that have been scooped out of the piston to clear the valves. But apart from that I'm equally
I looked long and hard at the combustion chambers around the valves etc and the two just look the same.
I did notice some slight differences in the size and shape of the oilways running up from the head gasket mating surface - so slight that they can't really have any functional effect. But would suggest that the two heads didn't start life as exactly the same casting.
We're carrying on with the swap and I hope to have the engine running tommorrow.

Keep me posted as I will be interchanging many components in spare head for Euro race spec parts in the coming months and was wondering about compatibility issues(its always the random 1mm differences that bite you in the rear).

Well it works!
The Mondeo head fits fine on the Contour engine and everything went back together with no hitches. Some of the hydraulic valve lifters rattled for a while when the engine first started because the oil had leaked out of them whilst the head wasn't being used. After a few minutes they stopped making any noise.
The big question is whether the performance is up to the Mondeo engine. As we don't have a dyno tester here to be able to produce hard figures for before and after, we have to rely on road testing. We ran the car for a couple of hours yesterday and it feels good. I'm not sure to be able to say it's as fast as the Mondeo engined car but hope to borrow one of those GTec testers to do some comparative acceleration runs. To be advised.
As I haven't changed any of the parts within the heads – I mean the Mondeo head we just fitted has all the original Mondeo parts in it – I can't offer advise on whether the changes you want to do will be compatible. As I said before the two heads look the same apart from slight differences in the shape of the face of the valve head.

On a side note, you did use new head bolts for the switch right?