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W116 6.9 (6632) engine rebuild

Started by HPC, 23 January 2023, 04:39 PM

daantjie

Quote from: HPC on 09 February 2023, 05:53 PMI need to find a decent machine shop in the Dallas area.

See if you can contact member "jtucker".  He's in Dallas and I think he has a very good tech working on his 6.9.
Daniel
1977 450 SEL 6.9 - Astralsilber

Randys01

Ok.  If the motor is still in the car  then leave it there and let's treat this a top overhaul only.
The gap between the piston and the bore is the only real way of getting a handle on the likely condition of the block
et al.
So..
clean them up as much as possible.bores/pistons
1) are there any signs of scoring..discolouration of the bores?
2}is there any noticeable lip  at the the top of cly and piston
- ie what does the unswept area look like? check no 8 in partic.

3} do any of the pistons  look manky when viewed from above
- ie no dings
4} do any pistons show signs of obvious wobble in the bores?

All good?
 
So let's measure a couple of bores.

you will need a micrometer for this level of clearance
- i have found a vernier useless

Measure the diam on the unswept area...then compare with  a sample from the swept.  Do it again but at  90 degree.

Compare your unswept value measurement with the manual for quality control purposes.

From looking at the photos it's hard to say but I can't see anything that rings any  bells thus far.





HPC

Here are some pictures of piston and cylinders. 7 has a bit of unevenness, rest looks all good.  (i did not rotate the motor)

I need to get better measuring tools... I get 106.98 for the inside of cylinders 7 and 8. Cyl is stamped 1+ and piston 106.998 - which mean bore must have been 107.014-107.018
there is a noticeable gap between piston and cyl wall. a 0.4mm feeler gauge can go into the gap, you can also wiggle the piston a little bit up and down and left and right.

Correct me if I am wrong,
bore size when new is 107.00 to 107.02, repair stage is 107.50 to 107.52
piston clearance when new is 0.015 to 0.025 with a wear limit of 0.08

does this mean I have too much wear?

0.008 to 0.010 of wear is expected per 100,000 miles? not sure if this is in/mm..


rumb

Im more concerned with the extensive corrosion on side walls. Those cylinders are toast. Time for next size pistons.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS

daantjie

Maybe honing them will take care of rust?  Not sure just asking. 

I'm leaning more and more towards my initial advice of finding a known good used engine. 

You can easily go down a deep rabbit hole with doing a complete tear down and rebuild.  Remember this ain't no garden variety old Detroit mill where parts are cheap and plentiful.
Daniel
1977 450 SEL 6.9 - Astralsilber

rumb

I went back and reviewed all the pictures so far. The cam journal and lobes have wear/scratches/pitting. The Cylinder wall has pitting.  I might think that all that coolant in the oil for years was not kind to the engine. 

At this point it is best to take that engine to a shop and have them check everything.


If it ever comes to it I have a spare 6.9 engine.  I heard it run once briefly. I would need to finish removing the intake -2-3 broken bolts --- to fully inspect if needed.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS

HPC

It is crazy to think that the motor was running when I got the car, ran when parked...

I did find the guy who worked on jtucker's car, that engine was rebuilt in 2016 I believe,  since then some parts are NLA (like the intake valves). He looked at the heads and also suggested a shop should take it on...
Even Metric Motors in California is hesitant due to lack of parts availability.

So, I guess a good used running motor will be next best thing.

Randys01

Looks as tho she taken some water in thru no8 and 7 cyls. Seems to  be typical of these motors.
There is some corrosion on the bores. no8 looks worst.
If you look at the  top unswept area of the bores they look fine longitudinally and at 90Deg.

So really the area of some concern is the corrosion on bore 8 and how deep is it.
Now you won't find this in the Rolls Royce Workshop Guide to Perfection for Brand new Motors but a bore can stand a bit of wear and a bit of marking on the walls.
I can see someone has had a bit of a go with  some coarse wet n dry to clean them up a bit. It's hard to tell but it looks like one of the striations has reached the depth of the corrosion. Some of this is no more than discolouration...some of it has eaten into the bore.

Can you feel it with your fingernail when its dry?  can you feel it thru a film of oil.?

This is the only potential show stopper I've seen so far. If you can massage these nuances out, you're on your way to a safe and cost effective rebuild.  Anybody can send the motor away and spend 15K on it. If you rebore then its WW3.pistons..rings..gudgeons.bearings oh dear!!

So my philosophy with this project has been to fix what needs fixing as distinct from what would be nice to fix. ::) 

raueda1

Quote from: HPC on 08 February 2023, 12:03 AMExhaust valve stem ~10.92  spec 10.93-10.95
Intake valve stem ~8.87  spec 8.95-8.97

Not sure about the valve guide wear amount, but the play in the old guide is much more when comparing to a new guide. Even the new guide has noticeable play.

Waiting for the new exhaust valves to arrive, still searching for new intake valves...

Springs measure about 49.40 and 45.10mm

If I can find intake valves I can have the heads rebuilt. The big question is with this much wear on the heads, wil the block need to be rebuilt as well?

Wow, this is turning into quite a project.  Others are far more knowledgeable than I am as far as evaluating your engine.  Still, it occurs to me that whether you rebuild or find a new engine, you're still going to end up pulling the engine.  So why not just go for it, pull the engine and take out the pistons?  Then you can properly inspect everything and, if OK, try honing the cylinders.  Nothing to lose.  The cylinder corrosion may only superficial.  Good luck and cheers,

Also, I cleaned and remeasured my set of intake valves.  All measure within spec along the whole shaft. 
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

raueda1

Quote from: Randys01 on 13 February 2023, 02:20 AMLooks as tho she taken some water in thru no8 and 7 cyls. Seems to  be typical of these motors.
There is some corrosion on the bores. no8 looks worst.
If you look at the  top unswept area of the bores they look fine longitudinally and at 90Deg.

So really the area of some concern is the corrosion on bore 8 and how deep is it.
Now you won't find this in the Rolls Royce Workshop Guide to Perfection for Brand new Motors but a bore can stand a bit of wear and a bit of marking on the walls.
I can see someone has had a bit of a go with  some coarse wet n dry to clean them up a bit. It's hard to tell but it looks like one of the striations has reached the depth of the corrosion. Some of this is no more than discolouration...some of it has eaten into the bore.

Can you feel it with your fingernail when its dry?  can you feel it thru a film of oil.?

This is the only potential show stopper I've seen so far. If you can massage these nuances out, you're on your way to a safe and cost effective rebuild.  Anybody can send the motor away and spend 15K on it. If you rebore then its WW3.pistons..rings..gudgeons.bearings oh dear!!

So my philosophy with this project has been to fix what needs fixing as distinct from what would be nice to fix. ::)
I second that.  That was my approach when I fixed a bent rod in my engine (bent from hydrolock).  I just replaced the rod, connecting rod bearings and honed the cylinders.  Also a new timing chain and guides. No machining, no lower end, no crank seals (in hindsight leaving the old seals was a mistake).  It was pretty damn cheap since my time is free, and car runs great except when I'm messing with the WUR  ::)
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

HPC

Fix what needs fixing vs fixing what is nice to fix. True!

When taking the time to take things apart, you think it would be good to replace what you can. Like timing chain and guides. That I feel is a must do!  But when valves are worn past limit. Probably needs replacing. If they were still within spec OK - It would be nice to have a new engine, but not needed.

It is not a show car, nor will it be driven 20k miles a month. It will probably only do that in the next 10 years. 

I also don't want to do all this work, if it needs to be redone a few years down the line. Then I would rather do it properly now.

I will inspect the other cylinders more closely and clean as much I can. Do I coat the cylinder walls with anything special to protect while it is open?  I do need to turn the engine to clean and inspect all cylinders.

Still on the lookout for a decent set of intake valves/ heads, and or a decent motor. I should post a WTB in the sale section.

Thanks for all the input!

daantjie

For 6.9 parts check out

oldbenz.co

They're in Canada but I'm sure they'll ship to US.
Daniel
1977 450 SEL 6.9 - Astralsilber

daantjie

Here is a very timely video for you.  I actually enjoy this guy's channel, lots of old school tips:

https://m.youtube.com/watch?v=qQJ6LCOSvmI

Daniel
1977 450 SEL 6.9 - Astralsilber

HPC

Quote from: daantjie on 13 February 2023, 11:03 PMHere is a very timely video for you.  I actually enjoy this guy's channel, lots of old school tips:

https://m.youtube.com/watch?v=qQJ6LCOSvmI



Very interesting, thank you. I knew the markings in the cylinder was from factory honing, never realised they helped keep a layer of oil for lubrication.

HPC

 
Quote from: daantjie on 13 February 2023, 10:02 PMFor 6.9 parts check out

oldbenz.co

They're in Canada but I'm sure they'll ship to US.


I did speak to Arsen, he may have had some valves but no luck. He does have an almost complete motor :) We should be able to get it to Texas :)