timing chain tensioner - Aus 450SE

[s class]

I have here pompy's 450SE.  Its an Aus spec car, and the compliance plate is date stamped 01-1976.

The previous owner claims to have fitted a new timing chain.  I don't know whether the tensioner was renewed or not.  Anyhow, the tensioner currently on the car is a euro spec one - secured by two bolts, not three like the U.S. one.  What seems odd is that the cylinder head has the extra bolt hole, and port related to the air injection system, as on U.S. spec cars, and I'm wondering if the tensioner is correct?  The car does not have an air pump, and apparently not an egr either.  Ideas?

[TJ 450]

If there is no air injection, then there shouldn't be any problem using the Euro tensioner. My spare Euro engine has the same setup. I think PB was saying that all replacement heads have the provision for air injection, but there are plugs in the exhaust ports.

It would be the same deal with pre-ADR 27A compliant engines such as this.

Tim

[Big_Richard]

*optional* plugs for the exhaust ports when fitted to non exhaust gas afterburner models

[s class]

Thanks guys.  I gather you are saying that 1/76 is pre-ADR 27A rules.  Does this mean that the engine has euro-spec compression, or does it still have the reduced compression pistons?

[TJ 450]

Yes, July '76 was when 27a was introduced, if I remember correctly.

AFAIK though, they are still low compression, as I have set of pistons from a pre-'76 D-Jet motor and they appear identical, so there is a bit of confusion regarding this. I presume this car has D-Jet injection?

Tim

[s class]

No, the car is K-jet, which suprised me slightly in light of the 1/76 marking. 

[TJ 450]

Wow, perhaps this is the elusive in-between model? I was always under the impression that the changeover to K-Jet coincided with the introduction of ADR 27A, but I have not seen any hard evidence to support this.

Tim

[s class]

pompy maintains that this car was first registered in South Africa and never made its way to Aus.  The reasoning is that, although the factory was not officially supplying 450's in South Africa, if the first owner was influential and wealthy enough, he might have persuaded the factory to redirect a vehicle intended for the Aus market.  As far as I know, the W140 I had arrived under similar circumstances. 

Personaly, I think the car was delivered in Aus, and was exported very soon after.  The original South African rego documents list the date of first registration as 01-01-76.  By my understanding of these things, that date is a default entry in the traffic system meaning that the exact date is unknown - only the year is known.  Both of my 6.9's are private imports, and accordingly their rego documents are dates 01-01-7x.  Perhaps in defense of pompys view, the first registration number of the car, was in an old numbering system that went defunct in ?1977? I don't know exactly. 

[WGB]

Wow, perhaps this is the elusive in-between model? I was always under the impression that the changeover to K-Jet coincided with the introduction of ADR 27A, but I have not seen any hard evidence to support this.

Tim

I always thought K Jet production - worldwide - started in later 1975 for the 1976 model year which would have started about August 1975.

Bill

[s class]

I must make a correction - in the daylight I now see the compliance plate is dated 4/76.  Sorry. 

[TJ 450]

Here's a link to a page detailing ADR 27A, when it was implemented and what changes were needed to comply.

http://autospeed.com/cms/title_Emissions-Regulations-Part-One/A_2677/article.html

I would speculate then, that only D-Jet cars were sold here until after July 1st 1976. Coincidentally, my 6.9 was built in July 1976.

Tim

[s class]

Preparations complete for splitting the timing chain. 

Hope you like the psychadelic 1972 curtains used as rags....

[s class]

It appears the chain guides in this car may not be orginal, though I think the replacement was not recent.  The guides show perhaps 100 000km wear (mileage on car is 300 000), and are not totally brown.  I'm replacing the upper ones again as a precaution since they are not expensive.  The lower ones we may leave (since replacement requires removal of the timing case, damper, water pump, SLS pump etc etc. 

[WGB]

I assume you are changing the liner on the tensioner slipper as this is usually made of inferior material and looks like it will break up long before the others.

Bill

[s class]

Bill, yes, we are addressing the tensioner rail.  The liner does show signs of surface break-up.  Now one has two options, :

a) replace the entire rail
b) replace the lining only.

MB South Africa's official line is they refuse to sell linings only because apparently there have been so many comebacks due to liners coming loose resulting in destroyed engines.  This ruling applies to all MB engines here, not only M117's.  However, I discovered that if instead of asking for a "tensioner rail lining", but rather ordering by the part number, you do get supplied the lining. 

On my 450SL, I replaced the lining only, and really cannot see why this should be a problem, providing it is installed correctly.  I think some of the problems may come about because people try to unhook the old lining, and install the new one with the rail still in the engine.  I removed mine and did it on the bench. 

I have put pompy's options to him, and he has elected to change the whole tensioner rail.