No one plug, a lot lighter in colour than other five, on Vitesse

[daverclasper]

Hi. No one a very pale grey, all the rest a biscuit colour.

I think I read that Nick Jones once had this and it was the inlet manifold leaking a bit of water into the cylinder and cleaning the combustion chamber.

Have just done 300 miles of mainly Motorway driving and no noticable loss of coolant with my car.

Wondering if anyone had any ideas, seems a bit odd to me?.

So, wondering if it is running weaker, will it cause harm?.

Could it be too tight valve clearance on that cylinder (no idea myself)

Worth trying a cooler plug (by quite a bit, if they are obtainable?.)

Any ideas would be great.

Thanks

 

 

[Pete Lewis]

but you have just been running with a  split pcv diaphragm  

pete

[daverclasper]

Yes, though that was sorted before the 300 miles I've just done

[daverclasper]

Also Pete, I have been monitoring no 1 plug (and no 2, to compare) three times in the last 200 miles and the difference has been consistent 

[daverclasper]

Only just remembered, I think I had this issue (though milder) a few years ago and was advised, it may be around the manifold balance of the carbs, via a connecting tube. Was advised to richen the carb that fed the paler plug, so will give that a go

[Pete Lewis]

well manifold lenghts can affect the spread of mixture  

give it a small adjust see what you get   the balance tube will mask some effects thats why its there 

Pete

[johny]

Yes manifold not perfect (same as standard exhaust one as well) so always a bit of a compromise. Have you got a colourtune to see the combustion colour on number 1 Dave?

[Iain T]

Try swopping the plugs and see if you get the same grey colour on the problem cylinder. 

Iain 

[daverclasper]

Thanks.

Sold Colourtune a bit back Johnny, as thought I probably wouldn't use it!

Thinking about this, I'm wondering if this cylinder has been running weaker than the others, for a while, though has been masked previously and for a long time by the car running much richer than currently.

I'll explain. Car has for the past 9 years of ownership always returned about 33 mpg when cruising at my usual speed of 60mph.

Due to the hunting at idle issue (now resolved) I leaned the mixture quite a bit from usual. Car still ran well, so have kept it at that.

300 mile run recently and got 40.2 mpg!.

I thought the gauge had started to read optimistic, as it's a journey I do often.

Double checked the maths after filling up and Yes, 40.2 mpg.

Car has 3/27 diff and overdrive so pretty long legged. I always cruise at 60mph/2500 rpm.

 

 

 

[johny]

yes Ive never used mine much but in this case it would have been interesting to see if there is a noticeable difference between 1 and 2.

I know that for tuning smoothing is done inside inlet manifolds, especially at the divides, to balance the airflow to each cylinder so maybe your manifold has a particularly poor casting.... Great fuel consumption though!

[PeteH]

There was heated exchanges over the "should the ports be polished". Two distinct schools of thought, 1) doing so improved air flow OR 2) the "as cast" surface created turbulance and improved mixing. Great fun.😁 Making the Carb Inlet to manifold match though was always thought benificial. And On Twin Cylinder bikes, with single carb, using a tapered Manifold insert did improve Balance.

Pete

[johny]

yes it wasnt so much polishing I was thinking of ensuring the resistance to flow through each branch of the inlet manifold is the same. I saw a programme where they had a manifold on a flow rig and ground its internal dividers to achieve this but of course I suppose this is only really a problem at the high flow rates youd get in a tuned engine.... 

[Pete Lewis]

i woudnt keep getting paranoid about mixed plug colouring   

refir them if its running smooth and fine  just drive  plugs were a 10.000 mile service change not take them out at eevery run and worry about the colours between cylinders

there is a lot of variations  , dont let that drive you mad 

Pete

[Chris A]

33 minutes ago, Pete Lewis said:

if its running smooth and fine  just drive

Quite agree. In my case I don't know what colour the plugs are, what the mixture is like nor the timing. The car runs well will still hit 130 kph, if I'm brave (or foolhardy). Enjoy it until the car actually tells you something is amiss. . . .

 

[Iain T]

12 hours ago, johny said:

I saw a programme where they had a manifold on a flow rig and ground its internal dividers to achieve this but of course I suppose this is only really a problem at the high flow rates youd get in a tuned engine.... 

On my manifold I did exactly that. There's a write up on Chris Witors website. When I took my head and manifold to be sorted he looked at the manifold and said "ah you've already ground it down I'll check the flow". As cast it can cause uneven flow to cylinders 6 and 1. However I only did the mod as I was doing a full engine recondition. 

Iain 

[daverclasper]

9 hours ago, Pete Lewis said:

i woudnt keep getting paranoid about mixed plug colouring   

refir them if its running smooth and fine  just drive  plugs were a 10.000 mile service change not take them out at eevery run and worry about the colours between cylinders

there is a lot of variations  , dont let that drive you mad 

Thanks.  I'm dead chuffed car appears to be getting such good mpg (wish I'd leaned if off a lot years ago)

Was just concerned about the almost white colour on the one plug (maybe even paler if I did a Motorway plug chop?) and possible damage to that cylinder.

I've no idea of the threshold/parameters for possible damage?

Cheers

[daverclasper]

On 03/09/2022 at 18:02, daverclasper said:

Thanks.  I'm dead chuffed car appears to be getting such good mpg (wish I'd leaned if off a lot years ago)

Was just concerned about the almost white colour on the one plug (maybe even paler if I did a Motorway plug chop?) and possible damage to that cylinder.

I've no idea of the threshold/parameters for possible damage?

Cheers

Hi. I'm aware this is not a counselling forum, though any thoughts to put my mind at ease would be great and I won't hold any individual, or the club responsible for advice, if the piston melted, etc.

Cheers, Dave

 

[johny]

Dave, youre sure theres no extra air going in that cylinder from some where? Go round the manifold gasket with starter spray or similar to see if the revs change...

Also I forget now but I assume youve tested compressions and checked valve clearances?

[daverclasper]

Thanks Johny. I had thought about the extra air, I think I need to take the filter box off and also the splash guard of to get proper spray access?.

I think, I did mention above, if I should check valve clearance? (I couldn't work out in my head if it would affect it?) ,though don't think I had a response, though I can check them.

I have thought about compression, if low then not enough fuel/air drawn in?, so could run weak?. I can check compression.

[Pete Lewis]

Dave the fikter box is the wrong side of where you need to test  youre after a leak test on the manifold to head gasket face 

you can squrit oil or even petrol onto the edge of the manifolf gasket 

valve clearance is important use rule of 13 to check when cold at 0.010"  

rule 13  is 12 rocker  down   check  rocker 1   and so on   till you have done all 12 

Pete

 

[daverclasper]

Thanks Pete. I have sprayed the manifold to head joint with brake cleaner around the top area and as much as I could to lower area, though wondered if I had to spray directly at the lower area as well, hence removing the gubbins for access.

I did check valve clearances, about a 1000 miles ago, though will check again

[johny]

Yes the valve clearance could be interesting because rather than melting pistons running weak is more likely to cause exhaust valve seat recession so the gap closes up...

[Pete Lewis]

suprisingly many inlet gaskets will breathe in stuff like petrol/brake cleaner when you spray the edge of the gasket  its the way they are made up of a mix of materials 

anf a good few makes will show a suck in if you squirt stuff , odd as that may seem 

if you checked the tappets a 1k ago they will be fine 

think you are chasing your tail on this so much depends on so many things in the way mictures and such are spread across the engine 

i would  just DRIVE IT   and not have too many concerns at odd differences between cylinders youre not going to melt a piston or anything disaterous

do check there is no side slop wear in the dizzy spindle / give the rotor a good push sideways   as wear here alters the points gap as it rotates 

if you have electronic  who's is it    some were known to have errors in the trigger magnet positions 

Pete

 

 

 

[johny]

Yes to the electronic ignition trigger so its interesting to check the timing with a strobe on number 6 cylinder which of course should be exactly the same as where you set it on number 1....

[daverclasper]

Thanks, it's put my mind at rest (until the next time!).

Will do a strobe test out of interest, if I get the time, as is running points. I do have a Simon BBC? cheap E.I unit, that I took off when tracing a fault years ago, that wasn't due to it. So I could put that back on, as would that eliminate any dizzy shaft play ? (as has always had a few thou's play).