Rolls-Royce and Bentley Forums banner
41 - 60 of 70 Posts

·
Registered
Joined
·
3,442 Posts
Personally, once the heads were off I would have updated the valve stem seals to Posiseals (Enginetech S-2980) and cleaned up the valve seats and examines the valve stems for unusual scuffing within the guides.
 

·
Registered
Joined
·
3,442 Posts
One was replaced with a used one according to the post.
 

·
Registered
Joined
·
41 Posts
Discussion Starter · #44 ·
Has he even taken the heads off ?
I have not disturbed the heads, but have inspected with boroscope.
Personally, once the heads were off I would have updated the valve stem seals to Posiseals (Enginetech S-2980) and cleaned up the valve seats and examines the valve stems for unusual scuffing within the guides.
I haven't experienced any oil burning on this engine (are the oil seals from '85 really cotton and wax valve stem seals?)

But good suggestion, thank you both, will do that (assuming the valves move freely)
 

·
Registered
Joined
·
261 Posts
Can I ask does your car have the rear crank shaft sensor if so how do you put the flex plate /ring gear back in the same place as every other manufacturer has 1 bolt out of line so ringear can only go in one place but not Bentley it seems !!
hi maybe I need to post a new thread as I’m just curious
but what if you don’t put the paint say you have a car with damaged ring gear and need to swop them out how do you time them. I’ve checked the manual and it don’t say. But the four tabs for the crank must align with something or does it just use the rear sensor to know it’s running but the front for reference purposes
 

·
Registered
Joined
·
3,442 Posts
Everything you need to know regarding engine rebuilding is laid out in the workshop manuals.
 

·
Registered
Joined
·
41 Posts
Discussion Starter · #47 · (Edited)
hi maybe I need to post a new thread as I’m just curioushttps://youtu.be/w3psDs-S4C4
but what if you don’t put the paint say you have a car with damaged ring gear and need to swop them out how do you time them. I’ve checked the manual and it don’t say. But the four tabs for the crank must align with something or does it just use the rear sensor to know it’s running but the front for reference purposes
No idea, not lucky enough to have a crank sensor
 

·
Registered
Joined
·
596 Posts
I have not disturbed the heads, but have inspected with boroscope.

I haven't experienced any oil burning on this engine (are the oil seals from '85 really cotton and wax valve stem seals?)

But good suggestion, thank you both, will do that (assuming the valves move freely)
Could be, RR was slow to change things, unless someone already changed them out.
If you remove the rocker cover(s) and see an inner smaller valve spring, they are more then likely still there.
Do as Wraithman says and check the build sheet.

If they are the cotton and wax seals and the car isn't producing blue smoke on deceleration, then they are OK.
However, cars that sit for long periods of time are problematic when it comes to those seals.

The cotton that is always being compressed by the inner spring does a great job of keeping any oil off the guide and stem when the car sits for a long period of time.
Water from condensation and bad storage habits cause the cotton to absorb the water and other impurities in the cotton.
With everything in that area dried out and corrosion at play, you end up with sticky valves.

This problem is reduced considerably with a modern Viton garter seal.
 

·
Registered
Joined
·
41 Posts
Discussion Starter · #50 ·
Well I checked it and then checked it again, all torqued up and happy, I have a distributor that turns again, yay!

Hood Motor vehicle Car Automotive design Automotive exterior
 

·
Registered
Joined
·
596 Posts
The line that is beside TDC is Top Dead Centre, not the lettering.
So where you have it now, it looks to be a about a couple of degrees out, but that's so little I don't think it would matter, it's not a race engine.

I would be interested to see what the compression is on all cylinders when it's all back together.
It would be a perfect time since the intake manifold is off.
 

·
Registered
Joined
·
349 Posts
The line that is beside TDC is Top Dead Centre, not the lettering.
So where you have it now, it looks to be a about a couple of degrees out, but that's so little I don't think it would matter, it's not a race engine.
There are no other way to mount it, so IMHO it looks good. There are no chain to move one teeth left or right ;) . Anyway, I'm curious if the engine will work good after end of montage.
 

·
Registered
Joined
·
41 Posts
Discussion Starter · #53 ·
The line that is beside TDC is Top Dead Centre, not the lettering.
So where you have it now, it looks to be a about a couple of degrees out, but that's so little I don't think it would matter, it's not a race engine.

I would be interested to see what the compression is on all cylinders when it's all back together.
It would be a perfect time since the intake manifold is off.
All cylinders between 110 and 125 psi, sounds reasonable for a 60K mile engine , given that it hasn't run for ~5 years.
 

·
Registered
Joined
·
41 Posts
Discussion Starter · #54 ·
There are no other way to mount it, so IMHO it looks good. There are no chain to move one teeth left or right ;) . Anyway, I'm curious if the engine will work good after end of montage.
yep, A1 is on the rock and the camshaft gear setscrews went in easily. Cylinder pressures look reasonable at 110-125psi, so fingers crossed.

Have to leave it for a few weeks but will post when I try to start it....
 

·
Registered
Joined
·
596 Posts
All cylinders between 110 and 125 psi, sounds reasonable for a 60K mile engine , given that it hasn't run for ~5 years.
We'll see, that seems a bit low to me for a RR V8, Wraithman would know off the top of his head, 125 is not too bad, but 110, my MK VI is 115, and that is considered a low compression engine with its rather large combustion chamber.

Two weeks will be a long wait.

Sorry to be skeptical, but if the valves were stuck enough to bend the push rods, I'm thinking that some were open enough for the piston's to come in contact with at least 2 of them.
A bent valve head that is only slightly bent won't be seen with a borescope, and would show low compression like that, even on an engine that has been sitting for 5 years.
 

·
Registered
Joined
·
41 Posts
Discussion Starter · #56 ·
We'll see, that seems a bit low to me for a RR V8, Wraithman would know off the top of his head, 125 is not too bad, but 110, my MK VI is 115, and that is considered a low compression engine with its rather large combustion chamber.

Two weeks will be a long wait.

Sorry to be skeptical, but if the valves were stuck enough to bend the push rods, I'm thinking that some were open enough for the piston's to come in contact with at least 2 of them.
A bent valve head that is only slightly bent won't be seen with a borescope, and would show low compression like that, even on an engine that has been sitting for 5 years.
You worry too much :)

Only tested with rubber tipped compression tester, couldn't find my screw in adapter. It'll be fine.

Of course, whether it will keep running reliably is another matter entirely, because as many have commented, we don't really know what caused this whole catastrophe in the first place...
 

·
Registered
Joined
·
596 Posts
When it comes to machinery, I like to have specific explanations of what caused the failure.
And I think the cotton and wax seals are to blame _ and sitting for 5 years.
 

·
Registered
Joined
·
41 Posts
Discussion Starter · #58 ·
When it comes to machinery, I like to have specific explanations of what caused the failure.
And I think the cotton and wax seals are to blame _ and sitting for 5 years.
Could be, also I was wondering if maybe the rear brake accumulator over pressured? That would fit the original description.

Did check all the valves and none of them were sticking…
 

·
Registered
Joined
·
596 Posts
So the valves have become unstuck then, but initially the sticking valves caused the push rods to bend.
I suppose that is as good of an explanation as any.
 

·
Registered
Joined
·
3,442 Posts
The brake pump push rods are designed to "fracture" if there is any over pressure issues with the pressure regulator or accumulator.
 
41 - 60 of 70 Posts
Top