Inlet valve guide part number (for a 1980 450 engine)?

I need a new inlet valve guide but am having trouble finding the correct part number, according to the new "EPC", it is A1160503624 (but is not recognised in MB online parts search), but most other sources say it is A1160504724.

TRW equivalents are 81-2685 and 81-26118, both seem to be available.

Does anyone know which one is correct or the differences between the two?

Hi Jim,

I can't help regarding proofed information abput 450SL but when I changed the valve guides at my 560SL I found out, that you better make sure what's in your engine befor ordering new parts. As I remeber, at least one of your valve guides was loose, so for that problem you must order a valve guide with first or second oversize diameter. As I crawled the net for new parts I saw differences in legth even when the partsnumbers were identical, so I measured them berfore ordering.

In general, these parts are built and made very easy and if leght and inner/outer diameter fits, you will be fine, but there may be differences in the mounting geometry of the valve seals and the position of the fixing ring.

Anyway: You need to check the diameter of the (probably) worn bore in the cylinder head to make sure to get the appropriate new part. There are to repair-oversices available and a little work will be necessary to tune the fit between new thicker valveguide und old worn bore in the cylinderhead. Once you are doing this all the worn inlet guide, check the clearence of all others valves too.

Best regards Martin

PS: Just for information:

That's what how guides perform (old/new)
sternzeit-107.de/de/forum/forum-107/2133...ch-ampelstart#212318

560SL

Outlet Valve Guide:
Lenght: 50,5mm, Inner Diameter 9mm -> Fit: VAG96139B
Outlet Standard A1160505324 (15,034-14,051mm)
Outlet 1. oversize A1160505524 (15,20mm)
Outlet 2. oversize A1160505624 (15,40mm)

Inlet Valve Guide:
Lenght: 47,5mm, Inner Diameter 9mm
Intake Standard A1160504724 (14,034-14,051mm) -> Fit: VAG96144B
Intake 1. oversize A1160504924 (14,20mm)
Intake 2. oversize A1160505024 (14,40mm)

Thanks Martin, my plan is to buy both standard and oversized guides ahead of time so I have a few to try when I start the job. When I changed the valve stem seals last winter I did find one loose one on the inlet valve on cylinder 1.

Depending on the fit I may give the guide a light knurl and glue in place with Loctite 648 as I have no access to liquid nitrogen for a shrink fit.

The valve stem seal job was very successful, I no longer get a puff of smoke at start up, however the spark plug in cylinder 1 has very bad oil contamination and build up after only 1000km. I am hoping this is caused by the loose guide.

It seems like the 450 and 560 have the same inlet guides then as these are the same part numbers I have found.

Vielen Dank, Martin. Mein Plan ist es, sowohl Standard- als auch übergroße Führungen im Voraus zu kaufen, damit ich einige ausprobieren kann, wenn ich mit der Arbeit beginne. Als ich im letzten Winter die Ventilschaftdichtungen ausgetauscht habe, habe ich eine lose am Einlassventil von Zylinder 1 gefunden.

Je nach Passform kann ich der Führung eine leichte Rändelung geben und mit Loctite 648 festkleben, da ich für einen Schrumpfsitz keinen Zugang zu flüssigem Stickstoff habe.

Die Ventilschaftabdichtung war sehr erfolgreich, ich bekomme beim Start keine Rauchwolke mehr, aber die Zündkerze in Zylinder 1 weist eine sehr starke Ölverschmutzung auf und baut sich nach nur 1000 km auf. Ich hoffe, das liegt an der losen Führungen.

Es scheint, dass die 450 und 560 die gleichen Einlassführungen haben, da dies die gleichen Teilenummern sind, die ich gefunden habe.

Hi Jim,

installing new guides is not the problem, but to get the right press fit may be tricky. In the WIS-Documents they discribe a special measuring tool to determine the exact diameter oft he bore.
Don’t use Loctite or knurl it!
For the installation I just heated the cylinderhead with a heat-gun. It takes a little time but it worked perfect. At the beginning of my "study" I also put the new guides in the freezer but this is complete useless. During the installation after a couple of seconds they will have the same temperature as the cylinderhead. WIS says that you need to heat the head up to 80°C, so just heat it up to at least 100°C and it will work fine.
For the installation (an de-installation) I used a set of parts, shown in the pictures. You need to lubricate the threaded rod very well, the force for pressing a new guide into the bore is pretty high and that will stress the tread – the thread in the nut as well.
To prevent the aluminum of the head from damage, I uses copper tubes. You need to replace them after 2-3 procedures, because of deformations. With this hombrew-tool the installation oft he guides was stressful but worked well. To process one guide this will be perfect.

Best regards
Martin

Thanks for the procedure and the pictures.

You will not approve of this, my plan is not to remove the head rather to do the repair in situ, this is why I plan a light knurl and loctite. I will have to push the guide back down over the top of the valve which will still be in place. If it holds, then good, if not I will then remove the head.

Can you tell me which part number you used for your repairs, original, oversize 1 or oversize 2?
What was actually worn on your car, the original guide or the recess in the head?

Hi Jim,

yes, really can't recommend this. After installing a new valveguide you have always to check the clearance between valve stem and the guide and mostly to rework with an expanding reamer. Due to pressfit the guide shrinks a little bit and so, during heatup the valve could stick. Than you have the same problem as before.

I used the original sized guides. At my engine the guides were worn out. The clearance between valve stem an guide was increased tremendously an the engine burned a lot of oil.

Best regards
Martin

Hi Jim,

I forgot an importend thing. After a change of the valve guides normally there is a treatment of the valve seat inserts necessary. Becaue the alignement of the new guide will allways be a littlte different compared to the old one. So the valve won't seal adequate and this cylinder then may suffer under a lack of compression.
Especially if you try to fit the new guide from the top without sufficient guidance during the fittingprocess.

It may become as good as before, but it won't become well.

Best regards
Martin

I spoke to an engine builder, he said, don't knurl or use a new guide, reuse the old guide and glue in place with high temp loctitie. He said it may hold or may not, if not, take the head to him for reaming and an oversize guide.

Hi Jim,

that sounds like a smart compromise. You avoid a lot of new trouble and may solve the main problem.
And if not, you can proceed with the big program.

May the force be with you
Martin

Here are the preliminary results after ~100 miles of driving.

I roughened up the surface of the old guide and reinstalled it with high temperature locktite glue designed for holding bearings and bushes in place.



This is a picture of the spark after 900 miles with the loose guide.



And now after ~100 miles with the guide glued in place. It has a slightly strange colour which I will monitor going forwards. However I feel pretty good about the success so far.

Hi Jim,

great Job! If it won't work for eternity, you can take off the head later anyway.
Better good botch than bad work

Martin

Hi Martin, how did you go about resizing the inside diameter of the new guides that you fitted. The workshop manual says to ream, however I have also seen "ball broaches" and hones being used.

Hi Jim,

I was lucky to borrow an adjustable reamer.
It wasn't much to ream, but it's really important that especially the outlet valves have a little play. Otherwise during warmup the valve shaft expands faster than the valve guide and this will end up in sticking. Your engine starts fine and then after about 30s it will die - if you don't know this failure mode, hard to find.

Cheers Martin