Valve Stem Seals

[garrycol]

My RV8 is smoking just after start. It is a 4.6 with old 3.5 Strombergs on it. Has been rebuilt over a few years including the heads - probably only covered 500km since rebuild - the crankcase breathers have not been connected up as yet so are open to atmosphere.

When you start the engine it runs fine and has no smoke - after about a minute it starts to smoke quite badly - oil smoke not fuel. Then as it warms up and gets to operating temperature all smoke disappears.

Does this sound like leaking valve stem seals? If so it is possible to replace the valve stem seals with engine and heads in place - if so how is it done.

Thanks

Garry

[garrycol]

Just some additional information.

Changed the spark plugs today - all show soot from running rich - the ignition at the moment is EDIS 8 running on default mode so only 10 degrees BTDC is available and I live at the top of a long hill so without ignition advance going up the hill under a bit of load and no advance a bit of unburnt fuel sooting the plugs a bit is to be expected - though with it also burning oil after start I would have expected burnt oil deposits. Cylinders 3,4, 8 where just a little wet but not much in it.

After the plug change I started up and no smoke at all, where yesterday it was like fog. Quite inconsistent.

Any thoughts would be appreciated.

Garry

[DaveEFI]

Have you checked the crankcase ventilation is clear? Take off the oil filler cap, and check there is a slight 'suck' there.

[garrycol]

I have the drivers side connected to the inlet manifold but not the passenger side which is just open to atmosphere (need to fix that before too long). With the engine running there is a little suction on the side open to the atmosphere. That is a similar arrangement to an injected 4.6 where the inlet manifold sucks in the fumes from the drivers rocker while the inlet is in the inlet side just upstream from the throttle body where it takes in filtered air. This differs from the 3.5 engine and carb setup (that I have on the 4.6) where ports under the carbs suck in engine fumes from each rocker but the air inlet for the crankcase ventilation is at the back of the block and has a fuel style filter to keep the nasties out of the crankcase.

Cheers

Garry

[Ian Anderson]

Answer to initial question can you do valve seals without removing heads.

Answer is yes.

Remove spark plug, feed in some rope when the piston is at BDC and turn engine up to compress said rope against valves. You can then remove collets and springs without dropping valve into cylinder.
After that the valve seals are visible.

Never done it myself but heard it has been done numerous times.

But before I did anything like this I would put another 1000 km on the engine and have done an oil change to normal oil to clear out assembly and running in oil.

Ian

[garrycol]

But before I did anything like this I would put another 1000 km on the engine and have done an oil change to normal oil to clear out assembly and running in oil.

Ian

Thanks Ian - when it first started blowing smoke I did drop the running in oil and put in normal oil just in case it was the running in oil was the problem. While the engine does clear itself after a bit of driving and it warms up, I cannot take it on the road as it is as the smoke is too think - like a fog. It is a danger to other road users and because of the pollution hazard the authorities will pull it off the road. What gets me is that like today when I started it there was no smoke at all, yet yesterday it smoked out the neighbourhood.

Thanks for the tip on the valve seals but how do you compress the springs to get the collets out etc.

Cheers

Garry

[Ian Anderson]

Have you got an oil pressure gauge! Perhaps the oil bypass relief valve sticking and pressure too high pushing the oil to where it should not be!

Perhaps flowing to much to the rockers and flooding above the valve seals, and then once the oil warms it drains away fast enough not to flood up there?

Just conjecture of course.

Ian

[stevieturbo]

Answer to initial question can you do valve seals without removing heads.

Answer is yes.

Remove spark plug, feed in some rope when the piston is at BDC and turn engine up to compress said rope against valves. You can then remove collets and springs without dropping valve into cylinder.
After that the valve seals are visible.

Never done it myself but heard it has been done numerous times.

I have done the above...and it takes a surprising amount of rope ! lol But it does work

[GDCobra]

I have done the above...and it takes a surprising amount of rope ! lol But it does work

May be worth taking the drain plug out of the sump and making sure the rope isn’t coming out of there.
That would indicate a more serious issue!

Seriously though, that’s a god d tip, I’ve heard of a similar practice with compressed air but the rope sounds simpler.

[stevieturbo]

I have done the above...and it takes a surprising amount of rope ! lol But it does work

May be worth taking the drain plug out of the sump and making sure the rope isn’t coming out of there.
That would indicate a more serious issue!

Seriously though, that’s a god d tip, I’ve heard of a similar practice with compressed air but the rope sounds simpler.

Compressed air is good in theory, but the biggest problem is getting the collets unseated, which can often take a little tap on the retainer with a socket/hammer. If you do not have enough air pressure, or when you tap the valve opens and you lose all air pressure....it would be extremely difficult to unseat the collets to allow you to use a tool to remove them.
At least with rope, it gives you a solid base against the valve.

I just use thinnish blue nylon rope, have the piston a bit down the bore, shove a lot in, and then rotate so the piston locks up tight against the valves.
It means no matter what happens the valves will never drop anywhere bad. If you lost the air seal for any reason with compressed air, the valve could drop.

[garrycol]

Thanks for all those comments - no oil gauge at the moment just the light so not sure of actual pressure. This a project that is slowly coming together so a lot of things are jury rigged or not installed just yet.

Progress has stalled due to this problem and a couple of other things that have cropped up.

Starting to get jack of it and am thinking about putting the old 3.5 back in and doing a basic pull down of the 4.6 then putting on an engine run frame and doing the injection as originally intended and when all sorted putting that back in - at least with the 3.5 I can use the vehicle as this project has been going for 6 years.

Thanks to everyone who has commented.

Garry

[garrycol]

For the last three days there has not been any smoke at all - very confusing.

[DaveEFI]

At such low miles, it might still be bedding in. My check for valve seals is to rev it quite high then snap the throttle closed. The maximum vacuum is then more likely to pull oil in down the stems. Or, of course, as I said before, crankcase pressure.

[GDCobra]

I have done the above...and it takes a surprising amount of rope ! lol But it does work

May be worth taking the drain plug out of the sump and making sure the rope isn’t coming out of there.
That would indicate a more serious issue!

Seriously though, that’s a god d tip, I’ve heard of a similar practice with compressed air but the rope sounds simpler.

Compressed air is good in theory, but the biggest problem is getting the collets unseated, which can often take a little tap on the retainer with a socket/hammer. If you do not have enough air pressure, or when you tap the valve opens and you lose all air pressure....it would be extremely difficult to unseat the collets to allow you to use a tool to remove them.
At least with rope, it gives you a solid base against the valve.

I just use thinnish blue nylon rope, have the piston a bit down the bore, shove a lot in, and then rotate so the piston locks up tight against the valves.
It means no matter what happens the valves will never drop anywhere bad. If you lost the air seal for any reason with compressed air, the valve could drop.

I agree having something semi-solid in the bore is better than that compressible air.
I've never done it either way myself so I'm not speaking from experience but if it did use air I think I'd take the piston to TDC or thereabouts so that if a valve did drop it would not go far and presumably still stick out of the guide.
Mind you I guess I'd always be expecting to have to whip the head off anyhow. I'll like the idea of this rope method.

[GDCobra]

At such low miles, it might still be bedding in. My check for valve seals is to rev it quite high then snap the throttle closed. The maximum vacuum is then more likely to pull oil in down the stems. Or, of course, as I said before, crankcase pressure.

Agree with that, give it some time it may sort itself out. What's the worst that could happen?