XUD Different Cylinder Heads

[Pug_XUD_KeenAmateur]

mostly just curious really, and drawn a blank googling the slightly different engine numbers....

...that PSA have made at least two slightly different cylinder head castings, for no particular reason?

The dirty oily one is my spare engine from a 'M' 306, there's so little clearance between the raised part immediately left of the cylinder head bolt that I can't get my Injector socket in there to pull out No.4 Injector

The clean one is my fitted engine in my 'N' 405, no such issue with access for the Injector socket

Both engines are 1905cc na's

Engine numbers provided but of course they could be a Red Herring coz they relate to the Blocks rather than the Heads

[CitroJim]

Differences as far as I'm aware are limited to three things: early ones have square exhaust ports; later ones have round ports and the final ones deleted the timing hole on cylinder 4. The timing hole had a screw in it that looked a bit like an extra head bolt.

All heads as far as I believe are interchangable.

[CitroJim]

Except between XUD9 and 11 of course.... They're not so easy to swap around!

[spider]

Mine had the timing hole / plug in the head but had the later Lucas pump so it was not really needed. I can't remember the year it went awol I'd guess 93 or so. The later "no need" pump I think started about 1990.

This may be irrelevant information...

Oh the 1.8's the head design changed in 1991 a bit as (apparently) they would crack a bit, the design was modified to prevent this. Mainly a change of webbing I think. I can find specifics. Mine had the earlier one from what I can recall though without problems. I should point out this is a 1.8 only thing as far as I know.

EDIT... 1.8: TD heads only as far as I know. It was in the water channel area. I'd have to check a BOL or similar to get specifics however.

[CitroJim]

The timing hole seems to have been deleted with the introduction of the Bosch AS3 semi electronic pump so around 1996....

When did the Lucas DPC go semi electronic Andy?

[spider]

The timing hole seems to have been deleted with the introduction of the Bosch AS3 semi electronic pump so around 1996....

When did the Lucas DPC go semi electronic Andy?

Jim, as far as I'm aware (this is likely something you already know!) the use of the 'timing plug' was removed when the later pump did away with the need to have two DTI's (a messy thing at the best of times)

Pumps: Mid 1996 for both pumps although the 'gotcha' here is it depended a bit on the car. For instance *all* 406's have the electronic pump but no 405's do and no 306's do either (XUD / DT units only, DW8 is a different kettle of fish)

This despite 306's being built after the 406 but with the mechanical pump.

I hope that makes sense.

Most electronic ones do away with the fast idle thermovalve assembly (but not all of them)

I'm aware Xantia's were mixed. I'd expect ZX's to follow the 306 pattern and retain the 'mechanical' pump but I'm not 100% sure on that. It would make sense as its the same car.

[Pug_XUD_KeenAmateur]

thanks Jim & Andy, much appreciated as ever

[Peter.N.]

They had different camshafts according to application, the Peugeots had a vacuum pump drive on the r/h end, the hydropnumatic Citroens didn't.

Peter

[CitroJim]

They had different camshafts according to application, the Peugeots had a vacuum pump drive on the r/h end, the hydropnumatic Citroens didn't.

Later ones did so that the EGR and fast idle actuators could be 'powered' from vacuum via the vacuum pump as used on the Pugs to supply the brake servo. The cams are easily swappable Peter... The heads are 'ready' too with a blanking plate covering the necessary bits...

Cams were different between Turbo and Non-Turbo too... The Turbo cam was a bit softer.. Not metallurgically but profile-wise!

[Peter.N.]

Thanks Jim, never got involved with any late ones, even my 2.1s only went up to '96.

Peter

[spider]

Not metallurgically but profile-wise!

"cam-o-three" ?