Timing Housing - gasket or no gasket ?

[les87GTE]

As we all know there was a change with the timing housing/oil pump requiring/not requiring a gasket after engine number 20E 0347985. My question is - what changed? Did the timing housing change in size (albeit fractions of a millimetre) or did the gears change in order to compensate for the lack of a gasket. If the housing changed - which housing part numbers require a gasket and which one's don't? Reason for asking is that my engine number suggests that I don't need a gasket but the housing number is not the one listed for my car on the parts microfiche (1987 2.0E GTE Exclusive Coupé). So should it or shouldn't it have a gasket. The timing housing listed is 638100 / GM 90008592 but the housing fitted is GM 90090599 (not mentioned on the microfiche) or is it the gears? Are the gears at +0.2mm the difference, and if so, to suit which housings? Complicated I know but, if anyone has any idea which goes with which I would much appreciate it.

Steve.

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[H-400]

Hi Steve, to be sure you'v got to check how far the gears stick out of the oil pump house. Pré '85 engines need a gasket and the gears stick out 0mm-0,1mm. Engies from '85 need only sealing compound and stick out 0mm-0,65mm. So the gears of both timing houses are the same, it is the depth that is a bit different. To check:

Fig 1.18

Very rare: Some timing houses have a 02 stamped into the pump house Fig 1.20 but they need gears with oversize dimensions. In more than 35 years I never saw such a timing house.

[GTEPETE]

Herman, do you know if  there a supply of new 2.0 or Frontera 2.4 front timing covers in Europe, both have been NLS in the UK for a number of years...Luckily I have 2 nearly new 2.4 ones but was thinking of the future...

[H-400]

They are very hard to find, even in Germany. And "new old stock" will cost you your right arm. The only thing that worns out is the inside of the oil pump, to solve that problem you need oversize gears that fit in a bigger milled oilpump house. But untill now I'v never heard about that solution.

[cam.in.head]

yeah the books mention it but ive never seen it either. think it was larger diameter shafts rather than actual gears but not too sure .

as for the wear that occurs on the actual housings .in the real world and even with a scored housing they are usually fine, the only result of a worn housing is lower pressure at idle only( same as a worn endplate or leaking releif valve.)any other issues with pressure not going to 4.5 or 5 bar upon higher revs  are down to the releif valve spring ( hence release pressure).

a very good pump in a very good engine running 20w/50 can easily manage 2 bar at idle when hot .

[les87GTE]

Herman - thanks again for your input regarding the timing housing issue. I can confirm that my housing does NOT have a 2 stamped on it but I'm still curious as to which car/engine it was originally intended for. I have, however, recently acquired a new pair of gears for the oil pump said to fit all CIH engines. Sadly, the drive gear is the one with a slightly larger shaft, as mentioned above by cam.in.head, and does NOT fit into the oil pump housing that I have. Do you know what car/engine this would fit and would it be a 'crime' for me to have it engineered smaller to suit my needs or should I sell it on? The driven gear appears to be exactly the same as my original in all dimensions.

cam.in.head - my oil pressure does exactly as you describe above. At idle (as soon as revs drop below 1000rpm) the light comes on and whilst driven oil pressure climbs to 3 - 5 bar depending on speed etc. Oil used is VR1 20w50, timing housing is known to be pretty good with minimal scoring and end plate with release valve is brand new.

[cam.in.head]

ok then. if your housing is good and the cover and releif valve is all good then you are losing some pressure when the pump is producing the least amount of pressure ( ie low revs)so this can point to a few areas.

gasket fitted to cover when it shouldnt have one.

worn gears.

worn crankshaft shells.

worn camshaft bearings.

missing or blown out blanking plug in oil gallery in the rocker feed.this is an approximately 8mm dia plug on the very top of the head between a couple of the rocker arms. ive only known this to happen once but that proves it can and the result was very low idle pressure.

wrong grade oil.20w/50 (thinner oils can obviously be used but will result in a lower idle pressure.)

with regards to your new gears id say its easierto have the gear shaft machined down than having the bush bored out.?

so if it were me id check the head first and then the gears.

[les87GTE]

Thanks again cam.in.head. All good information and will be checked out in the next two weeks (work commitments, sadly) and we'll see how I get on.