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MG MGF Technical - Manifold misalignment

Whilst fitting a VVC inlet manifold to a VVC head the machined mating face was out of alignment on the LH side needing some 3-5mm of the sholder removing from the head before the manifold would sit flush with the head face! This was quite unexpected and could be a source of problems if refitting a new or replacement manifold to a head or vice versa especially if the head /engine is in the car and vision is obstructed. The potential problems could be poor running and even stripped threads if care is not taken. This could also apply to the fitting of the VVC inlet to a 1.8i. If any one wants pictures let me know.

Yes please - and so will Dieter! :o)

This is the second time you've reported problems with this casting Mike - what is going on? Certainly explains the variation in performance you sometimes see with VVC engines!
Rob Bell

Mismatch between manifold and head on 1.8i is greater, especially when you remember that the VVC inlet port is 3mm higher on average than the MPi casting. There is often a small mismatch between the upper and lower manifold halves too. I haven't seen the problem that Mike reports but it is niot something that should be seen as too much of a surprise.

Roger Parker

This interests me as an area where a standard engine need not necessarily be 'modified' as such, but with careful attention to alignments, significant power gains can be found...

Rog, I hadn't appreciated that this applies as much to the plastic manifold (as I assumed that an injection moulded plastic part would be more accurate than a cast metal part that is then machined?)

Worth my investigating a bit further perhaps?
Rob Bell

Rog, this misalignment was not between port apertures but the machined inlet face of the head, in the top left corner,the milling tool has stopped short leaving excess material on the face preventing the inlet manifold stud holes from fully aligning, hope that makes it a bit clearer.
This has occured whilst replacing one VVC head for another and reusing the existing manifold, I would not expect to see this and hence the warning for others.
Will forward pictures ASAP.

Rob,Rog,Dieter/MOD, you have mail.

not so fast, me is already beyond fifty !
Dieter Koennecke

Thanks Mike :o)
Rob Bell

Forgive me, but is that really a lot of diffrence (where to where are we concerned about?) looking at the measurement from the centre of the bolt to the centre of the hole? how is the flange at 10cm used?

Last night I was pondering how you could tell a misalignment, and I came up with some sort of dye, flushed thru the exaust, with the aim after to 'polish' away any metal with dye on the mating face- am I so far off i'm talking a diffrent language?
Will Munns

Will, there is no need for concern, this note was mainly for those people who like to remove and swap parts about and in this case even though we were swapping like for like we found a problem with the replacement parts. HTH

Hi Mike,
The reason I ask is because I am planning on having a play with a midget, a 216 and plenty of spare time...
when you gas flow a head do you worry about the mating surfce in the exaust, or are you just interested in the low pressure side of the engine?
Will Munns

Lads,this is my inlet manfold face you are discussing, this is from a Jan 1997 VVC, which was returned to Rover after 3 weeks of ownership due to a broken VVC unit, my local Newcastle based dealer could not fix it, so Rover sent a complete "special" complete cylinder head for them to fit. I now realise that special means defective in Rover speak.
My frustration is that I reported misfires and coolant leaks to Rover, no fault found was the reply at 12000,24000,36000 and 48000 services.We have even pressure tested the cooling system for you!! I know the truth now, thanks a bunch Rover.
Mike is going to get the car for every service from now on, the 280 mile round trip is worth getting the job done properly.
Anyone else had this problem? This started with a little oil (or so I thought) in the water,I now know this must have been fuel.

Forewarded from an email Rog sent 8 hours ago:

VVC head on my bench, from a 1999 engine, measures 14.05mm.

----cut end ----

I think this should be kind of rated value.
Of course more then Mike spotted.

Dieter Koennecke

This thread was discussed between 20/08/2002 and 21/08/2002

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