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Garage => Mechanicals => Topic started by: HPC on 23 January 2023, 04:39 PM

Title: W116 6.9 (6632) engine rebuild
Post by: HPC on 23 January 2023, 04:39 PM
Hi Everyone,

Some advice and/or parts needed please. My 6.9 #6632 is need of an engine rebuild... I bought it as a project, in decent condition with 71k mi on the clock, except for an engine with blown head gasket/ possible overheating issue.  After removing the heads we discovered the valves are worn past factory specs, excessive for the miles. Which puts doubt on the integrity of the block (and the accuracy of the odometer).  How robust are the engines? Any way to tell if the block (and bearings) are still good without opening up, or move on and try to source a complete running engine?

To rebuild the heads - intake valves are NLA from MB classic center - any other sources to try?

Thanks
Manie
Title: Re: W116 6.9 (6632) engine rebuild
Post by: daantjie on 23 January 2023, 05:10 PM
It would be unusual for a 6.9 engine to have suffered such a fate but of course anything is possible.  Any idiot can ignore an engine temp gauge and run an overheated engine to failure of course.  As a rule the 6.9 engine is very robust and probably the most overbuilt engine Benz has ever made.

Having said all that, if indeed the motor has been severely overheated we must assume that it is now compromised and thus personally I would not try and drag a dead horse over the finish line.  You can usually find used 6.9 motors on ebay and such.  Likely some forum members here might have a spare motor kicking around.

You can usually find NOS parts on ebay.  There is a seller in Canada selling NOS valves for the 6.9 if you still want to go down that route.

Cheers
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 23 January 2023, 05:23 PM
Thank you Daantjie.  I am a bit weary of purchasing an engine out of a car, not knowing if it runs or not, I don't want to end up with 2 non-runners  :o   But if my block is OK, then doing a rebuild on the heads should is workable, if I can locate valves. I do have some part already like full gasket set, chain, guides, etc.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 23 January 2023, 07:00 PM
When you say valves are beyond spec are we talking valve stem dimensions OR we talking valve face/valve seat?

In order to assess how worn this motor is, what are the rocker arm pads like? No 7 and 8 usually have a story to tell.

By now most of these motors clap out the valves guides if they have been neglected...........is the wear in the valves more to do with wear on the guides?

What is then running clearance in the camshaft bearing towers?  Take 2 measurments of both.

What do the cyl bores look like?.scouring?..excessive lip at the  top.  partic No5?

What condit were the head gaskets? Blown around No 5?

I look fwd to your findings.

Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 23 January 2023, 08:49 PM
Valve stem dimensions... my mechanic says valves and guides needs replacing.

Not sure on the camshaft bearing towers

The cyl bores look OK, no scouring or lip.

I could not see any particular point of failure on the gaskets. I'm attaching pics that I have during dismantling, maybe you can spot something.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 23 January 2023, 08:55 PM
Here are some pics of the right side camshaft and rocker pads
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 23 January 2023, 10:00 PM
All looks pretty good to me..
cam lobes AOK 
cam bearings LOOK OK.

WHAT ABOUT ROCKER ARM TO CAM LOBE?

BUT.......how rich has this thing been running?.and not for a little while either?!!

So valves and springs huh?  with all due respect from 10000 miles a way I'd say not a problem.
They will have to be dismantled of course but to write them off arbitrarily  is a bit premature.
The springs can be measured for length/crush etc . and compression strength. I reckon they will scrub up ok.

The valves should be removed and clearance with the guide carefully measured. If the guide is worn -as these are prone to do-, the valve- once removed of springs etc- will wobble in the guide.
Take an observation of the valve stem at its end/tip and inserting the valve stem partially, see how wobble/play/wear you have. ie unswept area
I think you will find if there is anything worn, it wont be the valve but the guide. All pretty simple stuff. 

Love to hear your findings.


Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 23 January 2023, 10:32 PM
OK, so, the history that I have on the car...
1st owner in Oklahoma City had it for 10 years (1979-1989) and 32,000 miles, regular oil changes
2nd owner in Fort Wayne, Indiana, drove it for 3 years (1989-1992) and another 11,000 miles,
  total 43,000 miles with regular oil changes
then a dark period with 2nd owner, with no oil change records available, next oil change on record 10 years later in 2002 at 67,000 miles ( at MB dealer)
after this the car went into storage with 71,000 miles, and got pulled out by the son of the 2nd owner in 2013 who then discovered coolant in the oil.
Something must have happened between 2002-2005-ish and 4,000 miles to cause the issue
Between 2013 and 2022 the engine was periodically started to keep it turning over, with no coolant to get mixed into the oil. Maybe this cause the evidence of rich running, and maybe excessive wear?

When I got it, it would fire up easily (with a small puff out the exhaust) and drive a short distance to move it.

I found the radiator and coolant cavities filled with oil, thinking heads reconditioned and new gaskets would get it back on the road..

I may be in way deeper than expected...
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 23 January 2023, 11:11 PM
nice looking bus.
Yes.a bit of an interesting history.
Id say there is nothing major to this point with the motor.
The head galleries look fine.no major corrosion.
Anyway, I look fwd to your responses to my questions at 10pm.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 23 January 2023, 11:15 PM
Thank you for your observations, makes me feel more positive again.
I will take another look at the heads and valves and report back accordingly :)
Title: Re: W116 6.9 (6632) engine rebuild
Post by: daantjie on 24 January 2023, 01:50 AM
On a side note looking at the green puddle in the valley that is the wrong type of antifreeze for a Benz.

Once you button it up flush completely and refill with Zerex G-05 (Valvoline) diluted 50/50 with distilled water.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: raueda1 on 24 January 2023, 10:25 AM
This project is stroll down memory lane. ::)   Agree with Randys01 assessment (but lesten to him, not me, he's far more knowledgeable).  My question is, how far do you want to take it?  Engine needs head gaskets, not doubt.  And it's half taken apart.  You could do a head rebuild job, new gaskets and call it a day.  OTOH, you could pull the engine and do a more thorough job, such as replace all the chain guides, maybe crankshaft seals, replace the old and probably brittle wiring harness, rehone cylinders, inspect pistons etc.  I discovered that my engine had been rebuilt (+1 pistons) but chain gears hadn't been replace and were quite worn so those got replaced.  And do a nice repaint/restoration of the engine compartment while you're at it.  That's the rabbit hole I got sucked down, but in the end I'm glad I did.  Cheers,

ps - be sure to replace the valve springs in the right orientation.  They have an up and down that is not at all obvious!
Title: Re: W116 6.9 (6632) engine rebuild
Post by: daantjie on 24 January 2023, 12:30 PM
As well, if you do not need to pass smog testing, then now is the time to yank all that smog garbage off the motor and block off all the ports.  Once the engine is assembled it's a lot more difficult to plug all the ports. Especially the connection and piping at the throttle body, it's pretty much impossible to pull the recirc piping with the intake in place.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 24 January 2023, 12:41 PM
Quote from: raueda1 on 24 January 2023, 10:25 AMThis project is stroll down memory lane. ::)  Agree with Randys01 assessment (but lesten to him, not me, he's far more knowledgeable).  My question is, how far do you want to take it?  Engine needs head gaskets, not doubt.  And it's half taken apart.  You could do a head rebuild job, new gaskets and call it a day.  OTOH, you could pull the engine and do a more thorough job, such as replace all the chain guides, maybe crankshaft seals, replace the old and probably brittle wiring harness, rehone cylinders, inspect pistons etc.  I discovered that my engine had been rebuilt (+1 pistons) but chain gears hadn't been replace and were quite worn so those got replaced.  And do a nice repaint/restoration of the engine compartment while you're at it.  That's the rabbit hole I got sucked down, but in the end I'm glad I did.  Cheers,

ps - be sure to replace the valve springs in the right orientation.  They have an up and down that is not at all obvious!

Thanks for the advice, this is quite the big rabbit hole! 

I planned on doing the chain and guides along with the head job, gaskets, the rubber parts on the intake manifold and vacuum lines. 

The wiring harness is bit stiff towards the front of the engine but not bad.
There is some surface rust under the brake master and on the other side that needs treatment. not a complete repaint, a touch up of the affected areas.
I didn't think it would need new valves - but I will recheck that on the weekend and get a second opinion.
And the crankshaft seals I have heard needs doing at some point too...

I would also need to do the brakes, suspension and steering. So need to be careful how deep down the hole I go ;D

I need more hands to help
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 24 January 2023, 12:42 PM
Quote from: daantjie on 24 January 2023, 12:30 PMAs well, if you do not need to pass smog testing, then now is the time to yank all that smog garbage off the motor and block off all the ports.  Once the engine is assembled it's a lot more difficult to plug all the ports. Especially the connection and piping at the throttle body, it's pretty much impossible to pull the recirc piping with the intake in place.

Yes the smog stuff will not find its way back into the engine bay...
Title: Re: W116 6.9 (6632) engine rebuild
Post by: rumb on 24 January 2023, 01:46 PM

Yes the smog stuff will not find its way back into the engine bay...
[/quote]

As despicable and worthless as all that smog stuff is, you could completely kill yourself and future owners from ever being able to register or even sell the car.  CA CARB is spreading and many states just plain will never allow these cars on the road if they are missing components.

Even if your state can get by I would think heavily about removing it.  I recently sold 2 vehicles because they were missing smog components and I didnt want to get stuck with the thousands of dollars it would take to put back on them.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Rolo on 25 January 2023, 12:47 PM
I bought +1 pistons and rings from Mahle.  I ordered directly from Germany and they only have blueprints for +1 in Euro spec.  So you'll have to switch to premium gas on US spec motors.  The F1 shop made the pistons for me.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: raueda1 on 25 January 2023, 03:22 PM
Quote from: Rolo on 25 January 2023, 12:47 PMI bought +1 pistons and rings from Mahle.  I ordered directly from Germany and they only have blueprints for +1 in Euro spec.  So you'll have to switch to premium gas on US spec motors.  The F1 shop made the pistons for me.
FWIW, my +1 euro pistons were supposedly 8.6:1 compression not 8.8.  I learned this from some MB rebuild manual, can't recall which.   Regardless, I use premium.  However, I have used lesser gas a couple times and never had knocking problems and my timing is advanced significantly
Quote from: rumb on 24 January 2023, 01:46 PMYes the smog stuff will not find its way back into the engine bay...

As despicable and worthless as all that smog stuff is, you could completely kill yourself and future owners from ever being able to register or even sell the car.  CA CARB is spreading and many states just plain will never allow these cars on the road if they are missing components.

Even if your state can get by I would think heavily about removing it.  I recently sold 2 vehicles because they were missing smog components and I didnt want to get stuck with the thousands of dollars it would take to put back on them.
[/quote]. Interesting point.  Does CA CARB mandate emissions testing regardless of age?  Some states just waive emissions testing altogether after a certain age.  That's the case in both Utah and Connecticut (states of relevance to ME) if 25 years old or over.  Not sure how common this is. 
Title: Re: W116 6.9 (6632) engine rebuild
Post by: rumb on 25 January 2023, 06:01 PM
I have seen some state that CA CARB requires all cars after 1975 to get smog tested. I think 15 or so states copy CA currently.

But to what standard I dont know. CO has same as CA, but my 6.9 was tested at the 1977 tailpipe test standard. This was 4 years ago, so I hope nothing changed.


Since I have a unmolested euro I got a federal EPA exemption. My belief is that all unmolested euro 6.9's (as well as should all other euro w116) would be able to get this. Note the car must be in original config with no smog on it.

This would be rather good news at least for 6.9 as most are euros.


You can read the prior discussion on another forum where i mention the federal form:

https://www.benzworld.org/threads/grey-market-sec-smog.3112100/page-2


In the US it is rapidly getting to the point where people decide what state to live in based on which politicians are in control.

So the question is, do you want to be the person stuck with a car you cant sell or drive 10-20 years from now? The smog stuff is ugly but it really doesnt rob that much power. Its only going to get worse, not better with our old cars.

BTW smog pumps and EGR can all be rigged to be non funtional. Ive heard of ppl gutting the inside of air pumps so they look ok but do nothing. You could do same with EGR put on blanking plate and gutted EGR on top of it.

Title: Re: W116 6.9 (6632) engine rebuild
Post by: Rolo on 25 January 2023, 06:59 PM
Quote from: raueda1 on 25 January 2023, 03:22 PM
Quote from: Rolo on 25 January 2023, 12:47 PMI bought +1 pistons and rings from Mahle.  I ordered directly from Germany and they only have blueprints for +1 in Euro spec.  So you'll have to switch to premium gas on US spec motors.  The F1 shop made the pistons for me.
FWIW, my +1 euro pistons were supposedly 8.6:1 compression not 8.8.  I learned this from some MB rebuild manual, can't recall which.   Regardless, I use premium.  However, I have used lesser gas a couple times and never had knocking problems and my timing is advanced significantly
Quote from: rumb on 24 January 2023, 01:46 PMMahle only offered me one choice for +1 pistons.  Not sure what the comp ratio is, but I've tried midgrade, and it knocks.  Engine is running great according to the analyzer.  It's very strong.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 25 January 2023, 10:34 PM
Quote from: rumb on 24 January 2023, 01:46 PMYes the smog stuff will not find its way back into the engine bay...

As despicable and worthless as all that smog stuff is, you could completely kill yourself and future owners from ever being able to register or even sell the car.  CA CARB is spreading and many states just plain will never allow these cars on the road if they are missing components.

Even if your state can get by I would think heavily about removing it.  I recently sold 2 vehicles because they were missing smog components and I didnt want to get stuck with the thousands of dollars it would take to put back on them.
[/quote]

That makes sense!  I did not think of selling in future.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 30 January 2023, 09:44 PM
When we last left this post I enquired about the rocker pad wear where it rubs on the camshaft.....do you have a couple of examples you can post.? I'd be interested in the rockers from Cyl 1 and 5.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 06 February 2023, 11:53 PM
Hey Randy, I have the heads back, here are pictures from Cyl 1 and 5.  they all look similar. 

You can also see the wear on the valves, out of spec on the stems.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 07 February 2023, 01:29 AM
The original question was whether this motor was beyond repair..we've  looked at a number of what I would call "CRITICAL MARKERS" from the top of the motor. Everything IMHO looks a "go".
eg  Rocker wear seems remarkably good .

You have sent the heads out I presume to be dismantled. Now we can see the valves and they have  measured up under sized.
It's impossible to tell from a photo. how much have they worn?

But the million dollar question is how did the valve guides measure up.?

AND
what about the valve springs?  How did they measure?
 
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 08 February 2023, 12:03 AM
Exhaust 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?

Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 08 February 2023, 01:51 AM
Before going any further how true are the heads?
You can't take much off these before you run into problems of camshaft timing and valley cover  machining.


Meanwhile...examining the pieces.  This is rather odd.......
the inlets are worn worse than the exhaust.?
all valves are as black as pitch.?
it doesn't look like the exhaust valves have sat on their seat (s) for a looong time.???n

You have committed to a course of substantial overhaul.
1.you have new valve guides? The old ones are clearly worn as per normal.
2 new exhaust valves  on the way
3 inlet valves which are clearly well out of spec but no new ones on the horizon.?

What are the valve seats like?. They are going to have to be recut and faced anyway.

New valve stem seals of course.

You are going to have to consider new valve lifters.

moving to the lower part of the motor....how stripped down are you prepared to go?


 
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 08 February 2023, 02:09 AM
I have a theory about this motor. I'm just puttin' it out there.
After peering into these photos for some time and taking into account what has been reported I am hily suspicious that this motor has spent a lot lot lot  of its life running rich.

I'd wager a bet ... $5.00 !... that this explains the excessive wear on the inlet valves which  have been continually  running wet and thus deprived of lubrication. The combustion chambers are far too black as are the piston tops. By the time the whole  lot is burnt off the exhaust valves are black too BUT not excessively worn.
Maybe someone fiddled with the WUR so that it ran rich to compensate for the blown head gasket. dunno

But it raises the spectre of block wear could be similarly affected.

Time to take some accurate bore measuremnets unless the pistons are coming out in which case,.all will be revealed.!
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 08 February 2023, 06:44 AM
Running rich can be due to the last 8 years just starting the engine occasionally with fresh oil and no coolant to keep it going. The PO did mention having to do some work on the fuel system at some point due to not running well.

Considering the amount of wear... continue with a full rebuild (with some parts NLA), or stop here and look for a good running motor? Even if I can get the heads all new, you can't ignore the block.

I have sourced some parts for the motor already, but these may be better used on a motor in a better condition to start with.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 08 February 2023, 09:00 PM
The next motor is going to be an unknown. At least this one you know/are getting to know. 
Do an evaluation of the bore wear..check block deck height for trueness...........a straight edge will do.
Evaluate piston crowns.
Cylinder lip wear..the usual.
Are you taking the sump off?

On balance the motor has done nominal miles......I think i'd be forging ahead with what I know. Another motor would of course require everything you've done so far.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 09 February 2023, 05:53 PM
From what I can see the block deck is straight, I am a little concerned about the gap between piston and cylinder wall.

I need to find a decent machine shop in the Dallas area. I am a little reluctant to dive deeper in to the block, but I suppose it would be best to take off the sump to inspect from underneath.  The block is still in the car.  I can get the heads redone - still searching for those intake valves..  the rest of the parts for the heads seems to be available.

You are right, another motor is another unknown, unless I find a good running one with good history.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: daantjie on 09 February 2023, 06:10 PM
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.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 09 February 2023, 09:37 PM
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.




Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 12 February 2023, 04:06 PM
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..

Title: Re: W116 6.9 (6632) engine rebuild
Post by: rumb on 12 February 2023, 05:14 PM
Im more concerned with the extensive corrosion on side walls. Those cylinders are toast. Time for next size pistons.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: daantjie on 12 February 2023, 06:00 PM
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.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: rumb on 12 February 2023, 07:02 PM
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.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 12 February 2023, 11:49 PM
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.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 13 February 2023, 02:20 AM
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. ::) 
Title: Re: W116 6.9 (6632) engine rebuild
Post by: raueda1 on 13 February 2023, 03:24 PM
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. 
Title: Re: W116 6.9 (6632) engine rebuild
Post by: raueda1 on 13 February 2023, 03:37 PM
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  ::) . 
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 13 February 2023, 09:20 PM
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!
Title: Re: W116 6.9 (6632) engine rebuild
Post by: daantjie on 13 February 2023, 10:02 PM
For 6.9 parts check out

oldbenz.co

They're in Canada but I'm sure they'll ship to US.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: daantjie on 13 February 2023, 11:03 PM
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

Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 14 February 2023, 12:53 AM
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.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 14 February 2023, 12:57 AM
 
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 :)
Title: Re: W116 6.9 (6632) engine rebuild
Post by: raueda1 on 14 February 2023, 02:13 AM
Quote from: HPC on 14 February 2023, 12:57 AM
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 :)
Dude, I keep telling you I got a set of good used valves.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 14 February 2023, 08:20 AM
Im so sorry I misread your post :o
Thats awesome. I'll send PM.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 15 February 2023, 11:12 PM
Update on bore inspections..
stuck an iphone and light in each one to take pics in all directions.  a carbon buildup ring/discoloration on top of each bore. No 7 is the worst, the grey area is probably where water sat on top of the piston for a while, you can feel the roughness with fingernail. the rest feels ok. the diagonal dark line possibly where it leaked in from the head gasket.

Randy, there was no wet and dry involved in cleaning, just pb blaster and a shop rag. mostly to get the carbon off piston and the ring on the top of the bore.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 18 February 2023, 10:44 PM
So it's a matter of how much can we sand away the water damage in no7. The tracking I reckon you can get out with wet n dry.

However we hit a show stopper with the actual corrosion. This is typical of what you have described. Do you know, it doesn't take long.? For all the oil that is supposedly left on a bore after the piston has swept by, they corrode in a matter of months.
And not what's clear is why the gasket went in the 1st place.  and No7?.it's usually no 8.

Well we've arrived at the crossroads my friend.

In the perfect world we would pull her all down and back to Tours............7/10 thousand dollars.
Rebore..  no 1 o/s pistons /rings/bearings bla bla.
 
The problem here is that you cannot restore one cylinder without doing them all.
 So the way ahead is to restore No7 as best as possible and accept that she'll be as good as gold even with that blemish on the bore.
If it's done properly, you won't know.
I doubt that there will be any measurable drop in compression.
 I doubt that it will blow any smoke.
I doubt that it will use any more discernible oil.

So long as that corrosion is sanded back to the bore diam . ie the corrosion has not thrown a teeny weeny crust.

In your contemplation  just remember that another motor you might chance upon has probably the same issue...a benign leaking head gasket.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 21 February 2023, 02:39 PM
The corrosion spot is a valley not a peak... the engine is able to turn freely.

When I examined the head again, there is some corrosion on the head that formed a peak that could have caused the leak into the cylinder.  I still have not seen definitive proof of where the oil and coolant have mixed. I will get the  heads pressure tested to rule that out.

The PO provided me with compression test numbers if that is worth anything.
1 - 155
2 - 150
3 - 150
4 - 150
5 - 145
6 - 150
7 - 150
8 - 155
Title: Re: W116 6.9 (6632) engine rebuild
Post by: daantjie on 21 February 2023, 03:18 PM
Those compression numbers are not bad but not great either.  I would say at this juncture you need to ask yourself what you want out of the car.  Just a fun occasional cruiser, which most of these are now, or a very reliable daily driver.  Likely a 6.9 is not the best choice as a daily for mulitple reasons, so really if you want a Sunday cruiser, then it makes no sense to drop big coin on this motor.

If I were you and just wanted a fun type fair day driver, then just do the bare minimum to get it buttoned up again, maybe just hone the cylinders and get the heads done and call it a day.  The bottom end on these motors is very stout so unlikely you would need to do bearings I would think.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Gpapaniko on 22 February 2023, 05:42 AM
The fact that the compression ratios are roughly the same across the whole block is a good outcome.  I have much greater variability in compression across my 6 cylinder block and it serves me well as a Sunday cruiser.  I have more work to do on on vacuum leaks and the fuels system before I even consider doing the engine even if it is up to 400k kms.  If I keep the car for ever and do about 3000 to 4000ks per year, i will not add 100k kms to the motor. I agree with daantjie that align you strategy with the use case for car and the more time you have to enjoy the better value the purchase.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 22 February 2023, 06:20 PM
OK.compressions are pretty good.
Considering one or more is supposed to have a compression leak some where, it isn't showing up is it?
As matter of intertest the manual states that an 8.8:1 CR Euro motor pumps out 147 to 176 psi...so you are well with in range.
So there is no reason to abandon the  motor on this aspect.
If you have not scoured the bores, why is there so much evidence of cross hatching but in a random pattern?
By 100 K miles, the factory finish is pretty well gone.............?

By way of intertest I pulled the head off a Nissan Navara recently that had a blown head gasket......oh dear the head had to be thrown away but the point of interest is the water had sat in one of the cylinder for not a long time but it had a series of wave like marks in the bore.  From a cost effective point of view there was only one way to go. Clean her up using every trick in the book.. nail her up and away we go. Not a problem..cripes it stood every chance of blowing smoke but nary a drop.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: rumb on 22 February 2023, 07:34 PM
I've seen cross hatch on bores of MB engines over 100K several times.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 23 February 2023, 11:51 AM
My plan is not for a daily driver - I have a W124 400E for that. I would like to be able to do a little road trip now and again... 3000mi annually should cover it... 
The car shows 71k miles on the odo and I verified it is the original engine number. No evidence of it being opened before, so those must be the factory honing marks.
Should I take the oil pan off to inspect the bottom?
Is there a good way to flush out the oil and coolant cavities to remove any leftover sludge?
Title: Re: W116 6.9 (6632) engine rebuild
Post by: raueda1 on 23 February 2023, 05:50 PM
Quote from: HPC on 23 February 2023, 11:51 AMMy plan is not for a daily driver - I have a W124 400E for that. I would like to be able to do a little road trip now and again... 3000mi annually should cover it... 
The car shows 71k miles on the odo and I verified it is the original engine number. No evidence of it being opened before, so those must be the factory honing marks.
Should I take the oil pan off to inspect the bottom?
Is there a good way to flush out the oil and coolant cavities to remove any leftover sludge?
Not sure how to flush oiling system without actually running the engine.  Probably somebody else knows.  But something to think about is this - By the time you've undone everything enough to remove the pan you've done the worst part of  the work needed to pull it entirely.  And much of that is accessible from the top of the engine compartment.  If it were me I'd just pull it and clean up some other stuff too. And pulling it will greatly speed up a lot of other stuff that becomes easy if engine is out of the car.  Obviously I'm assuming that you access to big hoist etc.  Cheers,
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 24 February 2023, 05:11 PM
.Dave's pretty well covered it. Use compressed air to blow out the various holes,pull down and clean what you can get to.eg oil filter/oil resevoir/oil lines./oil cooler.

Flush/ purge/ heater/radiator hoses/therm etc

poss send radiator to specialistt for clean out.

When the engine is all back together leave the cam boxes off........new oil and filter..remove plugs/pull the coil etc and with plenty of rags at the ready crank the motor until you have oil pressure and can see all the old grungy oil coming out of the cam area. Do this a couple of times.  Mop up. These are a wet motor and the camboxes fill with oil quick smart.
After this purging exercise, close up .and run at idle for 10 minutes.
Drop the oil and filter and reload with new filter and oil.
In the meantime use your favourite coolant cleaner as per manuf reccos.

Make sure the engine is well oiled with an oil can used liberally over the valve gear.

Special note: hydraulic valve lifters. These are due for clean up. Remove from cyl head and crush them to expunge the oil within. They will need to be reloaded with fresh oil. This is a job no one ever does and perhaps best left to the workshop. You may of course choose to replace them all with new  ones.
You now have one very clean engine.
Title: Re: W116 6.9 (6632) engine rebuild
Post by: Randys01 on 06 March 2023, 07:09 AM
so what's happening?
Title: Re: W116 6.9 (6632) engine rebuild
Post by: HPC on 10 March 2023, 01:17 PM
Update!
Found a good euro motor base - thanks Rumb! Bores and heads seem to check out good. 
I think this is a much better base to start from.
guess it is time to get my old block out of the car...
Title: Re: W116 6.9 (6632) engine rebuild
Post by: rumb on 10 March 2023, 04:29 PM
My spare engine turned out to be in great shape! Valves and guides and bores all within spec. Glad it found a new home!

BTW this engine was out of 1976 with VIN serial number of 162.