smoke at idle

[martin_t]

Hi, I have raised this before, but it is still bugging me!! I am getting a trickle of smoke at idle (Cobra with RV8 3.5 and Holley 390 carb). I can smell it when stood at lights etc. The smoke dissapears when driving (I have had my wife watch me drive up the road and she insists it doesn't smoke under power).

I had bad smoke issues a while ago and this was caused by Valve stem seals and worn valves. I have since then changed the heads to Stage 3 ported heads with bigger valves from V8 Developements. They assured me they would slot straight on with no issues and they seem to be right. The car starts 1st time every time and runs fine, its just this trickle of smoke at idle that is doing my head in!!

Can anyone help or advise?

Thanks

Martin

[mgbv8]

Blue smoke, black smoke or white smoke ??
I assume the smoke is from the exhaust pipe and not from under the bonnet. ie breather issues??

Perry

[Ian Anderson]

What fluid are you having to top up?

That will point us at what is causing the smoke.

Ian

[martin_t]

Hi

The smoke is coming from both exhausts (twin pipes. four into each from the V8).
I guess its blue to white but difficult to tell, it even sometime looks black!!! The exhaust is quite sooty and yet the plugs are a perfect colour and dry.
I am not really topping anything up. I did an oil change at a thousand miles and moved from a basic 20/50 running in oil (Halfords classic) to Valvoline VR1. The car has now done 1600 miles.

Thanks guys

Martin

[sidecar]

Hi Martin,

I do believe that you have posted up this question before on the Cob forum and this forum. Really you need to get to grips with your carb or at least engage the help of someone that knows how to setup a Holley. From what I've read about Holleys they are not too bad to work on, there are many good books on them.

You could also do a leak down test to prove that the rings are OK, I presume that the heads and valve seals are OK as these will have been checked out by V8 Dev.

I'm sure that you are aware that running a rich mixture will eventually damage the bores and the rings.

Have you at least tried adjusting the pilot screws?

Regards,

Pete

[martin_t]

Hi Martin,

I do believe that you have posted up this question before on the Cob forum and this forum. Really you need to get to grips with your carb or at least engage the help of someone that knows how to setup a Holley. From what I've read about Holleys they are not too bad to work on, there are many good books on them.

You could also do a leak down test to prove that the rings are OK, I presume that the heads and valve seals are OK as these will have been checked out by V8 Dev.

I'm sure that you are aware that running a rich mixture will eventually damage the bores and the rings.

Pete

Hi Pete

Yes your right, I have posted before as mentioned, but my main problem is that I can't find anyone round here to set up or sort out the holley (if that is the problem).
Even though the car is running well the trickle of smoke at tick over annoys and worry's me.
Although I built the thing (of which I am quite proud considering my Zero mechanical knowledge before!!) I have pretty much reached the end of my mechanical skill set. I have taken on board what people have said on this forum and the Cobra one, especially about setting up the carb, and I have followed this. To be honest that made no difference.
Yes, the heads and valves etc., were done by V8 Dev, so I guess I have to trust someone and say they MUST be good!!
I did a compression test some time ago and the results seemed fine (according to Jim at JRV8 who I have a lot of respect for).
I am hoping that maybe the rings are not bedded in yet having only done 1500 miles but that is probably clutching at straws!!

So..........thats where I am...............!!

Thanks anyway and I will plod on over the winter to try and find someone who can set up carbs, and also looking for other issues that may be causing my slight smoking at tickover issue.

Cheers

Martin

[davemgb]

Martin,

Smoke at idle but plugs 'perfect colour' sounds odd.

Whether the smoke is oil or fuel the plugs should show something if the problem is serious. How are you checking the colour of the plugs. Ideally you should get the car hot so that the engine is at proper running temperature, any condensation in the oil or exhaust needs to be driven out before hand by driving a good few miles ( +20 ). The tail pipe needs to get too hot to touch otherwise you can't know if it's smoke or steam.

Then check on load condition by running under load and cutting the ignition with the engine out of gear, for idle conditions let it idle for a few minutes after it has been got properly hot on a run.

If you can disconnect the engine breather from it's catch tank or the carb then see if it is visibly breathing, if it chuffs like a steam train then you have a problem but if there is nothing being pushed out then the engine is not breathing out oil to cause the 'smoke'. Unlikely if your compression is good.

Regards,

Dave

[Ian Anderson]

Do you have brake boosters?
Could it be brake fluid being burned at max vacuum? (throttle closed)

Ian

[sidecar]

Hi Pete

Yes your right, I have posted before as mentioned, but my main problem is that I can't find anyone round here to set up or sort out the holley (if that is the problem).
Even though the car is running well the trickle of smoke at tick over annoys and worry's me.
Although I built the thing (of which I am quite proud considering my Zero mechanical knowledge before!!) I have pretty much reached the end of my mechanical skill set. I have taken on board what people have said on this forum and the Cobra one, especially about setting up the carb, and I have followed this. To be honest that made no difference.
Yes, the heads and valves etc., were done by V8 Dev, so I guess I have to trust someone and say they MUST be good!!
I did a compression test some time ago and the results seemed fine (according to Jim at JRV8 who I have a lot of respect for).
I am hoping that maybe the rings are not bedded in yet having only done 1500 miles but that is probably clutching at straws!!

So..........thats where I am...............!!

Thanks anyway and I will plod on over the winter to try and find someone who can set up carbs, and also looking for other issues that may be causing my slight smoking at tickover issue.

Cheers

Martin

Hi Martin,

You can not have "zero mechanical knowledge" because you built your car and the top end of your engine!.

Believe me, it does not take much knowledge to 'out knowledge' some of the people that sell their services as carb or engine experts. (Not all of them are that bad but some are).

I bet if you get a good book on Holleys and read it you could sort your carb out. Your plugs may look OK because the cruise and other circuits are OK, maybe just the idle circuit is rich therefore the plugs clean up when you give the car some stick. Of course I'm assuming that it is a carb issue! Does the engine use any oil?

One thing that I do remember reading in a Vizard book is that plug reading is less of a black art, it is more of a fallacy! (In other words a waste of time!) ..........He believes in using a Lambda probe.

Cheers,

Pete

[martin_t]

Hi Pete

Yes your right, I have posted before as mentioned, but my main problem is that I can't find anyone round here to set up or sort out the holley (if that is the problem).
Even though the car is running well the trickle of smoke at tick over annoys and worry's me.
Although I built the thing (of which I am quite proud considering my Zero mechanical knowledge before!!) I have pretty much reached the end of my mechanical skill set. I have taken on board what people have said on this forum and the Cobra one, especially about setting up the carb, and I have followed this. To be honest that made no difference.
Yes, the heads and valves etc., were done by V8 Dev, so I guess I have to trust someone and say they MUST be good!!
I did a compression test some time ago and the results seemed fine (according to Jim at JRV8 who I have a lot of respect for).
I am hoping that maybe the rings are not bedded in yet having only done 1500 miles but that is probably clutching at straws!!

So..........thats where I am...............!!

Thanks anyway and I will plod on over the winter to try and find someone who can set up carbs, and also looking for other issues that may be causing my slight smoking at tickover issue.

Cheers

Martin

Hi Martin,

You can not have "zero mechanical knowledge" because you built your car and the top end of your engine!.

Believe me, it does not take much knowledge to 'out knowledge' some of the people that sell their services as carb or engine experts. (Not all of them are that bad but some are).

I bet if you get a good book on Holleys and read it you could sort your carb out. Your plugs may look OK because the cruise and other circuits are OK, maybe just the idle circuit is rich therefore the plugs clean up when you give the car some stick. Of course I'm assuming that it is a carb issue! Does the engine use any oil?

One thing that I do remember reading in a Vizard book is that plug reading is less of a black art, it is more of a fallacy! (In other words a waste of time!) ..........He believes in using a Lambda probe.

Cheers,

Pete

Hi Pete

I built all the engine actually from a box of bits..........bottom up!! No one was more suprised than me when it fired first time!!!
It doesn't seem to be using oil, but then again, as I mentioned earlier, I have only done 1500 miles.
One thing, the smoke doesn't smell of petrol, more just like exhaust fumes.

Cheers

Martin

[martin_t]

Do you have brake boosters?
Could it be brake fluid being burned at max vacuum? (throttle closed)

Ian

No brake boosters Ian

But thanks for the input.

Regards

Martin

[john 215]

Hi Martin,

Manual or Auto ?

GM 180 box has a modulator on the box that when the internal diaphram goes bad allows the engine to suck gearbox oil in

just a thought

Cheers John

[sidecar]

I built all the engine actually from a box of bits..........bottom up!! No one was more suprised than me when it fired first time!!!
It doesn't seem to be using oil, but then again, as I mentioned earlier, I have only done 1500 miles.
One thing, the smoke doesn't smell of petrol, more just like exhaust fumes.

Cheers

Martin

My lump would have used 'an amount' of oil in 1500 miles, are you saying that you have not had to top up the oil in 1500 miles, if so then it ain't burning oil!

[DaveEFI]

Hi Martin,

Manual or Auto ?

GM 180 box has a modulator on the box that when the internal diaphram goes bad allows the engine to suck gearbox oil in

just a thought

Cheers John

I've had this happen a couple of times on my SD1 - and you get clouds and clouds of smoke. And the gearbox no longer changes up until you get to peak revs in that gear.

[martin_t]

I built all the engine actually from a box of bits..........bottom up!! No one was more suprised than me when it fired first time!!!
It doesn't seem to be using oil, but then again, as I mentioned earlier, I have only done 1500 miles.
One thing, the smoke doesn't smell of petrol, more just like exhaust fumes.

Cheers

Martin

My lump would have used 'an amount' of oil in 1500 miles, are you saying that you have not had to top up the oil in 1500 miles, if so then it ain't burning oil!

I changed oil at 1000 and hadn't topped up at that point. It may have used a little but not enough to warrant topping up. I tend to keep it at about half way between low and High on the dipstick.
Since the oil change I have done another 500 miles and not topped up as there has been no significant fall (maybe a tad but negligeable).

Cheers

Martin