Rover V8 and smoke

[WLAcopilote]

Hello,
something has been puzzling me: Rover V8 3.9 with SU carburetters - when I accelerate hard (about 2500rpm upwards) grey smoke comes out of the exhaust! I get black puffs under certain conditions (obviously overfuelling) Why is the smoke grey? A former colleague reckoned that grey or light brown smoke meant that the mixture was correct (something to do with particle size)- any one confirm or refute this?

Also there is a "ticking" noise on the over run, not valve train, wondered if it could be a dicky piston ring? Although as the engine runs, revs and pulls fine so I would be surprised if it was a ring.

cheers
Matt

[350zwelgje]

WLAcopilote said:

Hello, something has been puzzling me: Rover V8 3.9 with SU carburetters - when I accelerate hard (about 2500rpm upwards) grey smoke comes out of the exhaust! I get black puffs under certain conditions (obviously overfuelling) Why is the smoke grey? A former colleague reckoned that grey or light brown smoke meant that the mixture was correct (something to do with particle size)- any one confirm or refute this? Also there is a "ticking" noise on the over run, not valve train, wondered if it could be a dicky piston ring? Although as the engine runs, revs and pulls fine so I would be surprised if it was a ring. cheers Matt

Matt, a V8 will run smooth even when only 6 cilinders are ok.... So I would not take that as an indication that the engine is fine (especially with the description that you gave). Sorry can't help you on the ticking. Don't know what would make the colour of the smoke, but are you sure the carbs are mechanically sound and with a correct setup? I would start there, and perhaps the ticking disappears in the process (you never know).

Rob

[WLACopilote]

Rob,
carburetters (SU HIF6) replaced February 2003 with reconditioned ones. Heads skimmed and top-end rebuild this January. All plugs show evidence of combustion (I set the mixture up by pulling the plugs). Engine is definitely running on eight cylinders; I have heard them running on six and it is a very distinctive sound.

That said I will check the plugs again to be certain that all is well.
cheers,
Matt

[sliller]

Just a thought, have you checked the camshaft?, was it changed in the top end rebuild?. They tend to wear the lobes on cylinders 5 and 6 giving strange syptoms. Ive changed a few at about 70,000 miles. Compression testing may help.

[WLACopilote]

Thanks sliller, I will put a DTI on it and measure the lift. All the Rover V8's I have rebuilt have had bad lobe wear on number 8, less on number 7 and generally decreasing as you move forwards. Any idea on the ticking?

[350zwelgje]

Just trying: Came to my mind that I read of a pushrod not being ok, to be a source of ticking. Could be the cause combined with a camshaft lobe not being 'fresh' anymore. As I said, just trying.
Still puzzled by the smoke, should have known the answer over 10 years ago like that..... The getting older thing seems to get me.

Rob

[kevinday]

Ticking could be a leaky exhaust gasket. Or possibly a bad bearing somewhere in the belts route.

[steve_D]

Ticking noise is very common with exhaust leak from one manifold to head joint. It is also possible to put the gaskets in round the wrong way which results in only 2mm of seal which will not take long to fail.

Steve