Mixture Settings ??

[thebadleys]

Morning all,

After a 600 + mile drive today thought i'd look at the spark plugs as I'm no happy with the overall running/fuel consumption although it performed acceptably tester day.

I've attache photos of the spark plugs as removed and identified them by cylinder and banks, would appreciate comments, observations and suggestions.

Thanks
Nigel


IMG_2840.jpgIMG_2841.jpg

[jbuckl]

put 2,3,5 & 8 together and 1,4,6 & 7 together.

first group are correct / maybe a little weak, second are rich.

iirc first group are l.h carb fed, second are r.h carb fed.

iirc that means the rh carb needs to be leaned off a bit. (turn adjuster anticlockwise)

However, reading spark plugs isnt as easy today as it used to be due to changes in the pump fuels

[thebadleys]

Thanks Julian, didn't know the carb/manifold layout.

Nigel

[jbuckl]

well, im not 100% that i got it right either be nice to get a.n.others confirmation.

if the elbows are off, gently lift a carb piston 2 or 3mm up with your finger / a screwdriver.

The rich one will allow engine revs to rise.

The not so rich one will allow revs to rise then drop back down.

Thanks Julian, didn't know the carb/manifold layout.

Nigel

[marshman]

Post 8 in this thread by Klaus has a picture of what carb feeds what cylinder.

http://socforum.com/forum/showthread.php?20526-Spark-Plugs-Carb-question&highlight=Carb+manifold+feeds

Roger

[thebadleys]

Post 8 in this thread by Klaus has a picture of what carb feeds what cylinder.

http://socforum.com/forum/showthread.php?20526-Spark-Plugs-Carb-question&highlight=Carb+manifold+feeds

Roger

Thank you Roger, copy of diagram saved for reference, had a play this afternoon and will road test tomorrow.

Nigel

[marshman]

Hi Nigel,

Thanks to Klaus really for doing the diagram!!

I agree with Julian though that it looks like RH carbs needs weakening just a bit. However , if it was me I would start at the beginning and check ignition timing first, if on points just check they are not too worn. Check plug gaps and general condition of rotor arm and distributor cap. When happy with that side of things then check carbs for balance, correct operation of coke and throttle linkages etc, then finally tweek the mixture. (Probably teaching you to suck eggs, is so I apologise). Always found that best to tweak/check ignition first then adjust mixture last. I do usually go back and have a tweak of the timing to see if it will take a bit of extra advance. Not easy on an auto as I usually adjust so it just starts to pink on a wide throttle at low revs, on my Stag Auto its a bit more trial and error.

Roger

[thebadleys]

Hi Nigel,

Thanks to Klaus really for doing the diagram!!

I agree with Julian though that it looks like RH carbs needs weakening just a bit. However , if it was me I would start at the beginning and check ignition timing first, if on points just check they are not too worn. Check plug gaps and general condition of rotor arm and distributor cap. When happy with that side of things then check carbs for balance, correct operation of coke and throttle linkages etc, then finally tweek the mixture. (Probably teaching you to suck eggs, is so I apologise). Always found that best to tweak/check ignition first then adjust mixture last. I do usually go back and have a tweak of the timing to see if it will take a bit of extra advance. Not easy on an auto as I usually adjust so it just starts to pink on a wide throttle at low revs, on my Stag Auto its a bit more trial and error.

Roger

Thanks for that Roger, no egg sucking, all advice is very welcome, I remembered that some weeks ago whilst setting the timing that the vacuum advance was inoperative, I got a recon one from distributor doctor, fitted it and did not look at the general tuning as I was going somewhere in the Stag so need to remember to finish jobs off(its an age thing).

Interestingly the car has run quite well but felt it wasn't correct, am I correct that the timing is set with the vac pipe disconnected and engine revs at 3 - 3500 rpm @12 degrees ?

Thanks again off to my local Cricket Club for a drink (or 2) It called Stag Park.

Nigel

[marshman]

HI Nigel,

Hope the drink was good! I usually set mine to 12 deg static and advance it from there. I think it usually ends up around 15 degrees (static) when I have finished playing. But it does depend on your engine, compression ratio, pistons, fuel grade etc. I think early engines were specified to be 14 degrees and later ones 12 degrees, be nice if someone else can confirm. Beware of over advancing the ignition as it can cause overheating, burnt pistons etc.

Roger

[flying farmer]

Timing should be set at idle speed, at 3500 rpm it will be nearer mid twenties degrees for a mk2 or mid thirties for a mk1

Neil

[jbuckl]

Finally remembered something (IIRC)

Thanks for the link Roger & the diagram Klaus

Post 8 in this thread by Klaus has a picture of what carb feeds what cylinder.

http://socforum.com/forum/showthread.php?20526-Spark-Plugs-Carb-question&highlight=Carb+manifold+feeds

Roger

[jbuckl]

+1......sort electrical first, the adjust fuelling.

Hi Nigel,

Thanks to Klaus really for doing the diagram!!

I agree with Julian though that it looks like RH carbs needs weakening just a bit. However , if it was me I would start at the beginning and check ignition timing first, if on points just check they are not too worn. Check plug gaps and general condition of rotor arm and distributor cap. When happy with that side of things then check carbs for balance, correct operation of coke and throttle linkages etc, then finally tweek the mixture. (Probably teaching you to suck eggs, is so I apologise). Always found that best to tweak/check ignition first then adjust mixture last. I do usually go back and have a tweak of the timing to see if it will take a bit of extra advance. Not easy on an auto as I usually adjust so it just starts to pink on a wide throttle at low revs, on my Stag Auto its a bit more trial and error.

Roger

[thebadleys]

Hi all, thanks for your comments will act on them as soon as SHMBO lets me off gardening duty as it's very sunny up int' north ( really good Stag weather) but I can't play as apparently I've played to much this week.

Will report back as soon as I've made adjustments.
Thanks again
Nigel

PS Neil, fitted Secret Spoiler in anticipation of heat wave.

[thebadleys]

So, timing set at 12 degrees, vac pipe disconnected, to it for a run seems ok, got back forgot to connect the vac pipe, silly me get hold of pipe (engine running ) can't seem to feel any"pull" on the pipe, rev the engine, nothing, tongue over the pipe end, still can't feel any vacuum.

Some of you may remember that about a month or so ago I discovered my vac advance wasn't working so got a recon one from Dist Doc (very nice man and good service), then discovered that there was no vacuum from pipe and found the hole below the vac take off on the RH carb was bunged up, cleaned out and all appeared OK.
IMG_2768.jpgIMG_2770.jpg

Cant figure so I thought, why not take the vacuum from the front take off for the Themic Sensor, which doesn't work and is blocked off in the pipe (visual effect of being connected) did this, blocked off original take off on carb and went for a test drive, car goes better than its ever done I think, more power and a harshness that I got at higher speeds seems to have gone.

So, thoughts of the collective if you would be so kind.

Thanks


Nigel

[flying farmer]

Long time since I have dealt with the carbs, but I am pretty sure that the take off for the vacuum advance is closed off by the throttle butterfly when the throttle is closed, therefore you will not get any suck at idle.
By connecting the vacuum advance to direct inlet manifold vacuum you will get a lot more advance at idle and just off idle so the engine will feel a lot more responsive if it actually needs the extra advance, which yours obviously does if it feels that much better.
Full throttle advance will not be affected as there will be no manifold vacuum at full throttle so it should not cause pinking problems.

You may find your fuel consumption also improves if the engine benefits from the extra advance.

I must admit I have done the same thing on my modified engines before I went to fully mapped ignition, and the engine in my project Stag actually runs best with 52 degrees of advance at light throttle which is far more than is possible with the clockwork system. This is however a very modified engine with fast road cams, set up on a rolling road, and I wouldn't recommend that much advance on a standard engine!
Neil