Rover V8 engine smoking
Discussion
This is on a car I recently purchased. The engine was rebuilt 200 miles ago don't know what was done to it as all I have is a copy of the bill for over £2k so should have been pretty comprehensive. Anyway the car starts great has great power very smooth no noises etc. Start up from cold and no smoke whatsoever it only starts smoking (blue smoke) after its warmed up for a good ten minutes. There is no realy noticeable smoke while driving but leave it idling for a few minutes and it gradually gets worse and worse give it a rev and loads of smoke take it for a spin and it clears but comes back as soon as it's left idling.
My thoughts were valve stem seals but I would have expected it to smoke on start up as well and it doesn't. Tried with breather off and no difference.
The engine is a 3500 circa 1986 with Edelbroke inlet and Holly four barrel carb.
Pulled all the plugs and they are a medium sandy colour on the tips and a light sandy off white colour on the ceramic centre that was after a run. Leave it idling for a while until its smoking badly and a couple were a black sooty colour but not wet.
Would appreciate your views on this.
Chris
My thoughts were valve stem seals but I would have expected it to smoke on start up as well and it doesn't. Tried with breather off and no difference.
The engine is a 3500 circa 1986 with Edelbroke inlet and Holly four barrel carb.
Pulled all the plugs and they are a medium sandy colour on the tips and a light sandy off white colour on the ceramic centre that was after a run. Leave it idling for a while until its smoking badly and a couple were a black sooty colour but not wet.
Would appreciate your views on this.
Chris
Yes reconnected it and no difference plus the pipe was clear with no oil deposits just a bit of moisture which is to be expected with this set up.
I suppose it could be and inlet manifold gasket pulling in oil from the valley area under vacuum, I've not done a compression check yet but will do next weekend but really don't think it is piston or ring related but worth checking.
I suppose it could be and inlet manifold gasket pulling in oil from the valley area under vacuum, I've not done a compression check yet but will do next weekend but really don't think it is piston or ring related but worth checking.
Bennachie said:
Interesting to read this.............
My friend has a rover v8, relatively recently rebuilt, which exhibits identical issues to this one.
No oil smoke unless it sits and idles, then when revved it throws out smoke.
It too has an edelbrock etc. etc. It too has no PCV but a breather hose from the rocker cover to the filter. Cruicially, in my opinion, there are TWO breather hoses (one from each rocker cover) which are tee'd into the filter - this I think is the issue as the engine is not 'breathing'; there is no 'in and out' parts to the system. The original set up for the carburettor v8s was to have a pair of SU or Strombergs, which were constant vacuum carbs connected to the rockers and a third 'inlet' breather to the rear of the vee on the driver's side. The 'inlet' has been blanked off so the closed loop does not breathe. I suspect that the crankcase is being pressurised and oil is finding its way past the oil control rings under high vacuum at tickover.
The 'long descent on overrun' followed by the open throttle at the bottom produces no smoke and so it is suspected that the stem oil seals are ok.
Apparently the engine was run on a catch tank and a vent to atmosphere immediately after rebuild but the fumes from the open vent caused foul smells in the car.
I am looking to fit a PCV to one rocker and a filtered inlet to the other.
The problem is exacerbated by not being involved at the time of the rebuild and therefor not knowing exactly what was done during the rebuild - unhelpfully the owner has little mechanical knowledge and cannot help and does not remember what was done -'It was taken out, rebuilt and put back in'
Compression is fine and the thing goes well........apart from smoking after a long idle (more than 3 o 4 minutes)
I only have one breather on the drivers side rocker cover the other has the oil filler cap and a small capped breather on the back. I would be very interested in your findings with this issue I have asked a few people now and everyone is saying it's high vacuum related but where it is pulling in the oil from could either be valve stems, piston rings or valley gasket. My friend has a rover v8, relatively recently rebuilt, which exhibits identical issues to this one.
No oil smoke unless it sits and idles, then when revved it throws out smoke.
It too has an edelbrock etc. etc. It too has no PCV but a breather hose from the rocker cover to the filter. Cruicially, in my opinion, there are TWO breather hoses (one from each rocker cover) which are tee'd into the filter - this I think is the issue as the engine is not 'breathing'; there is no 'in and out' parts to the system. The original set up for the carburettor v8s was to have a pair of SU or Strombergs, which were constant vacuum carbs connected to the rockers and a third 'inlet' breather to the rear of the vee on the driver's side. The 'inlet' has been blanked off so the closed loop does not breathe. I suspect that the crankcase is being pressurised and oil is finding its way past the oil control rings under high vacuum at tickover.
The 'long descent on overrun' followed by the open throttle at the bottom produces no smoke and so it is suspected that the stem oil seals are ok.
Apparently the engine was run on a catch tank and a vent to atmosphere immediately after rebuild but the fumes from the open vent caused foul smells in the car.
I am looking to fit a PCV to one rocker and a filtered inlet to the other.
The problem is exacerbated by not being involved at the time of the rebuild and therefor not knowing exactly what was done during the rebuild - unhelpfully the owner has little mechanical knowledge and cannot help and does not remember what was done -'It was taken out, rebuilt and put back in'
Compression is fine and the thing goes well........apart from smoking after a long idle (more than 3 o 4 minutes)
Chris
Boosted LS1 said:
One other possibility, has it got a servo and do you ever need to top up the brake fluid? I'm just wondering if the seals there could be a bit ropey. I've no idea what colour smoke that could produce though.
Good point but no loss of brake fluid but I will pull the servo pipe and check that there is no oil present.Cheers
Just managed to get hold of the chap that I bought the car off. Apparently the engine was rebuilt due to burning oil he couldn't remember everything that was done but says he knows for sure that the heads had new guides (bronze) and stem seals all bearings were changed but he can't remember if it had new rings and a hone or if they were just checked and deemed to be ok but he is going to contact the engine builder and try and find out. He was told that the smoking was down to excess oil just burning off in the exhaust but I guess this is why he sold the car on not that I am complaining I bought it as a project at a fair price and as seen.
So knowing this information now it's unlikely to be the heads guides or stem seals I guess that leaves rings will do a compression first and if that shows ok I will have to invest in a leak down tester.
Chris
So knowing this information now it's unlikely to be the heads guides or stem seals I guess that leaves rings will do a compression first and if that shows ok I will have to invest in a leak down tester.
Chris
http://www.v8bb.co.uk/viewtopic.php?f=2&t=376e...
I had thought this but removed the exaust last weekend and it was pretty clear.
I have been Google searching and found the above link very similar to my situation rebuilt engine including rockers and shafts. The new rockers were flowing oil from them drowning the valve guides in oil which was then getting sucked into the combustion chamber. I have not run the car without the rockers yet but I did have the rocker covers off the other day and did make a mental note that there seemed to be a lot of oil pooled in the heads. Worth a try I have an old original set of rockers still on the shafts so a quick swap over is no big deal.
Chris
I had thought this but removed the exaust last weekend and it was pretty clear.
I have been Google searching and found the above link very similar to my situation rebuilt engine including rockers and shafts. The new rockers were flowing oil from them drowning the valve guides in oil which was then getting sucked into the combustion chamber. I have not run the car without the rockers yet but I did have the rocker covers off the other day and did make a mental note that there seemed to be a lot of oil pooled in the heads. Worth a try I have an old original set of rockers still on the shafts so a quick swap over is no big deal.
Chris
Edited by chris52 on Tuesday 28th February 20:28
X8Matt said:
I had the same problem on an SBC engine. If the Rover V8 layout is the same you will find that the inlet manifold actually performs three sealing jobs.
Firstly, it allows seals the route from the carbs to the cylinder head.
Secondly, it seals the lifter valley (the gap in the middle of the VEE) from the outside world, stopping oil leaking out.
Thirdly, it seals the lifter valley from the cylinder head
You might think that it is doing the first two jobs correctly, i.e no oil is leaking out and there are no obvious intake air (vacuum) leaks. However, if the manifold isn't quite 100% sealed against either of the cylinder heads, then oil mist can enter the cylinder head directly from the lifter valley. The engine literally sucks oil direct from the lifter valley, and of course will suck most at idle when manifold vacuum is highest. If you have had a new or refitted manifold then I would suspect this is the problem. Took me bloody ages to work this out, and fixing it wasn't straightforward either!
Very interesting and certainly worth investigating, thanks for the input every bit of help is appreciated. Firstly, it allows seals the route from the carbs to the cylinder head.
Secondly, it seals the lifter valley (the gap in the middle of the VEE) from the outside world, stopping oil leaking out.
Thirdly, it seals the lifter valley from the cylinder head
You might think that it is doing the first two jobs correctly, i.e no oil is leaking out and there are no obvious intake air (vacuum) leaks. However, if the manifold isn't quite 100% sealed against either of the cylinder heads, then oil mist can enter the cylinder head directly from the lifter valley. The engine literally sucks oil direct from the lifter valley, and of course will suck most at idle when manifold vacuum is highest. If you have had a new or refitted manifold then I would suspect this is the problem. Took me bloody ages to work this out, and fixing it wasn't straightforward either!
Chris
Bit of an update. Removed the rocker covers and although the rockers were OE they were dripping directly onto the valve springs and tops of the stem seals around 2 drops a second oil was literally pouring down the head and nearly overflowing. So I changed the rockers and shafts and the difference is like night and day only 1 drop every 10 seconds and only a slight flow of oil in the head. Smoke seems to have cleared a lot while just left idling but give it a rev and you still get a plume of blue smoke from the tailpipe only had it running on idle for about 30 minutes with the odd rev up to 3k hopefully this is only a build up of oil and crap that will just burn off over time.
The only thing I can think of is that either the shaft had been replaced with an aftermarket one or the rockers were just worn out.
Chris
The only thing I can think of is that either the shaft had been replaced with an aftermarket one or the rockers were just worn out.
Chris
Steve_D said:
But the only way that 'excess oil from the rocker shaft' can get burnt is if the valve stem seals are duff in which case you have still not 'solved' the problem just reduced it.
Steve
Not necessarily the fact that the valve stems were being drown in oil is hopefully the reason more oil than should be is getting past them. Fingers crossed it's all sorted now.Steve
Chris
Pupp said:
You'll probably have increased your effective oil pressure a tad too 
Excessive clearances on shafts and rockers bedevilled a lot of aftermarket components a few years ago with the rocker chests getting flooded, causing smoking and leaks. Glad it's sorted
Yes jumped up about 5psi on hot idleExcessive clearances on shafts and rockers bedevilled a lot of aftermarket components a few years ago with the rocker chests getting flooded, causing smoking and leaks. Glad it's sorted
Pupp said:
You'll probably have increased your effective oil pressure a tad too
Excessive clearances on shafts and rockers bedevilled a lot of aftermarket components a few years ago with the rocker chests getting flooded, causing smoking and leaks. Glad it's sorted
Yes jumped up about 5psi on hot idleExcessive clearances on shafts and rockers bedevilled a lot of aftermarket components a few years ago with the rocker chests getting flooded, causing smoking and leaks. Glad it's sorted
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