Almost done with this rebuild!

I kept looking at the valve stem seals that were installed - all 8 of them, and they didn't look new. I am just installing the valves after lapping them, and I decided to pull one off. Good gracious, definitely old and nasty.

I see several notes that only the intake valves have seals... um. Ok. But my exhaust valves had seals on them. Are the intake valves really the only ones that get seals? The engine rebuild manual says nothing about valve stem seals :eyeroll:

Cheers!

For closure (for now), I'm going with no seals on the exhaust valves simply because I can't fit the seals onto the guides and because I don't want them to stick up higher than the intake valves. The exhaust guides are too wide to fit the seals onto and don't have a cut-down section like the intakes do.

I'll let you know if it smokes, probably in 2021 haha. This is such a slow projwct, but it's all brand new to me.

Volvo uses both intake and exhaust valve guide seals on the red block motors.
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john

Is there some documentation for this? Even the BB FAQ implies that only the intake valve stems get seals.

Personal experience has found valve guide seals on both intake and exhaust. I have the tools to replace the valve guide seals while the head is installed on the engine and the engine is in the car, and I have done it.

When you buy a red block head gasket set you will find it comes with eight valve guide seals, not four.
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john

This debate may run and run!!!
For myself, I will probably continue using seals on inlets to avoid blue smoke, coke formation and poor emissions. For the exhausts, I don't really see the function, although I would use them if specifically required by the manufacturer.
It could be argued that the small amount of oil which gets past seals aids lubrication, and that the exhaust stems need to be without seals to get any oil at all !!

All best wishes for 2021 to all Volvophiles😊😊!!

Ian F

Hi,

I’m a little late spotting this post about intake valve seals.
I was thinking that an upper head gasket set only comes with four seals, for a two valve four banger?

I agree that they are not warranted to be on exhaust valves.
The reason they are used on intake stem guides is because of vacuum around the intake valve stem.
This is especially true when the throttle valve is suddenly closed up or even partially closed down rather quickly. The engine spins on while Driving in town and up and down hills.

This will cause the vacuum to continue on into the combustion chamber.
This also pulls oil up past the piston rings when the intake valve opens. Cars can smoke more when shifting as we all know.
Oil burning is contributed more to the piston rings and then it’s valve guides.
Also comes down to the amounts of circumferences!
The pistons are always working four times more to keep the oil down, where the intake valves are only one fourth of those cycle numbers.

I have often thought that the leaning of the cylinders over to one side slightly and having the intakes on the upper side, would help reduce oil exposure, besides, giving up more room for access to the intakes hidden components!

A vacuum cannot happen to the exhaust valves as the intake is never open to influence the exhaust valves because, they, the exhaust valves, open only on the other side of the combustion cycle.

The exhaust manifold causes more of a chance of the exhaust valves ports to be slightly pressurized. This is due to other cylinders firing and back pressure that builds up in the pipes and mufflers.

It stands to reason, with the reasoning above that the likelihood of the exhaust valves being hotter the seal would not last nearly as long.
The intake valves run cooler due to incoming air and fuel mixture flowing by.

Like you said, you don’t want a valve to stick due to lack of lubrication and have it start leaking. This is when the burning a seat ring or valve tulip.

This brings on a “True Heartache” with the way we love our Volvos.
Happy New Year to all!
Just working on being more of an vintage classic, than a has been!
(:-)

Phil

Some documentation - like the Haynes manual - implies it. The Volvo documentation is explicit: only the intake valves have the seals on the valvestems.

I did some more digging, even the 16V versions, the B204F and B234F, only have the seals on the inlet valves - albeit a different type, the same as the 850's 5 cylinder engines use.
This one seems to be of a different material (teflon?) and can also be found on the exhaust valves of later Volvo engines.

If you look trough forums, there's no concensus to the usage of seals on the exhaust valvestems. Some claiming it to be beneficial, others useless.
In one of the other Volvo forums there was someone who had installed seals on the outlet valves but found after 100k miles that they had lost their function. The heat of the exhaust valves had made the rubber hard and they had even come loose.

This confusion is the reason why I am so adamant that you check with the engine manufacturer first. Unless it's some well known and well documented design flaw that time unveiled and fixed - go with their design.

I see the same thing, so perhaps do a double and triple check? Lets do some digging...

Not that they know everything, but when in doubt, I also double check with parts suppliers. E.g. this one states explicitly: "Volvo 200, 300, 700, 900 with B200- or B230- Engine: The outlet valves have no stem seals, required quantity 4 pcs for one engine."

That probably means that at some point in the past your B230FT already had work done and someone installed the seals on all valves.

I can understand the confusion, if the rebuild manual doesn't specifically state them, it is easy to assume they go on all valves.

If I look at the overhaul procedures in the Haynes manual (200-series), it also doesn't state the number of seals used, but it does show a drawing pointing out the differences between an early type and a later type seal.
That drawing shows an inlet and outlet valve with the inlet valve clearly identified. Only this valve has the seal in the drawing.

Back to the source, Volvo. The drawing below shows part #17 to be 1306630, the valve stem seal. If you scroll down to part# 17, it lists all compatible engines ending with the word "intake".

As a general observation: valve stem oil seals are often used only on inlet valves to control the oil being drawn into the combustion chambers, and hence causing blue smoke and poor emissions. Exhaust valves don't draw oil into the combustion chamber as the chamber is at high pressure when the valve is open.
Ian F

That was the justification I came up with for it last night.

Also, the height and shape of the intake and exhaust valve guides make it seem like only the intakes are designed to accept a seal. The exhaust guides are taller - when the intake seals are installed, the top of the seal is equal to the top of thr exhaust valve guide. The intake guide is tapered so the seal will fit on. It is difficult to get a seal on the exhaust guides.

That may be a general rule, but in the end always check the engine requirements to be sure. There are many designs that do require valve stem seals on the outlet valves too, and Volvo engines that superseded the red blocks are no exception.

Intake creates vacuum, Exhaust creates pressure. Only need the seals on the intake. Keeps. the oil from being sucked from the valve cover side of the engine.

Agreed!!

Ian F