Dizzy - Plugs - leads

[JoeLondon]

Car is running great. I rebuilt the fuel pump last week due to failure there, everything is sweet and purring like a kitten, theres always been a slight wobble at idle like a V8, carbs are tuned well enough I believe, maybe timing miss? I don't know, it's never bothered me, doesn't impact driving, and it's not getting any worse so I've never chased it much.

Today I pulled the spark plugs just to check them since it's been a while.


Green side (Right bank - from drivers seat) seems to have the more questionable plugs 1&5 dark, 6 quite brown
The other side looks good, perhaps #1 is slightly dark.
I was reading the other threads on this, does any of this mean anything anymore?
Gaps were all at 32thou or so. I have set them now at 25thou - haven't driven it yet, runs fine, but it did already.
only one of the plugs is resisted, the other 11 are not, the leads are a total mix, a couple of 8mm leads, some unmarked and some that say resisted some don't. - Why do I get the sneaky feeling if I put this all right, the engine is going to run worse

I had a look in the dizzy and whatever the part is, pickup? was a crazy ball of brown furry rust, i've cleaned it lightly, brushed off the rust and hoovered it out, I didn't want to disturb much as I didn't want to upset anything unnecessarily. the spoked wheel also has spots of corrosion.



Getting to the point
I've ordered resisted plugs, NGK BPR6ES. I'll set to 25thou
I'll need new leads I guess. -
I have never seen dizzy internals with that much rust, the gasket under the cap is knackered, so I guess that doesn't help, but any other thoughts? Does that rusted part need replacing? Everything seems to be working just fine.
I found the tiny O-ring near the plugs after I put everything back, I didn't see it come off anything.

All this being said, the car runs really well, so, I'm also waiting for the "wasn't broke, why'd you try fixing it" monster to rear it's head.

Hopefully someone with less smooth brain than mine has an overall view?

[abowie]

does any of this mean anything anymore?

I have never seen dizzy internals with that much rust,

I found the tiny O-ring

With unleaded fuel plug colour is less useful. Having said this they all look on the lean side to me, and the difference between them is marginal if any. If the car's running well I wouldn't worry.

Neither have I. And your plugs were really rusty too. Do you live by the sea?

The o ring retains one of the 3 screws that hold the dizzy cap on.

[lowact]

You think it was running fine, maybe it could be running finer, or at least more efficiently.
I note you have a Lucas CEI type distributor; 1st used on fuel injected Jaguars. These had vacuum advance however I note yours is fitted with a vacuum retard module, maybe yr distributor is one of those mutated SNGB units?
Do you know if you have vacuum advance or vacuum retard? What you want is for the set-up and the distributor to be matching. Note this could be a cause of rough idling.

If the hose from the vacuum module on the distributor connects to the bottom of the left rear carburetor, you are set up for vacuum retard when idling. If it connects to the top of the carburetor, you are set up for vacuum advance when driving.

Disconnect the hose at the carburetor end and suck on it. if the pick-up sensor in the distributor moves anticlockwise you have a vacuum retarding distributor. If it moves clockwise, you have a vacuum advancing distributor.

If you can't hold the vacuum (with yr tongue) the vacuum module diaphram has a hole in it and needs to be replaced.

If you can hold vacuum but the pick-up sensor doesn't move at all you might be rusted up. Try to push the pick-up sensor around by hand, don't have to be precious, if it doesn't move or is a bit stiff use wd40 and push it back and forwards until it has loosened. It is not usual to see the distributor rusted like that, usually it is dry or oily. it looks like somehow it has been allowed to get quite wet and left to sit for a while?

If the distributor is not stiff/stuck it could be that the wrong module is fitted, i.e. the distributor can only move anticlockwise and yr module is trying to rotate it clockwise?

Leads will almost never be a cause of rough idling. If you start to get increased misfiring at high revs you would be wise to check or replace the leads, otherwise, "if not broke don't fix"

[JoeLondon]

Thanks Andrew and Colin,

Andrew, I'm not by the sea, I'm in Westminster London, but the car is a daily driver and parked outside year round, what I've spent on rust prevention I could probably rent a garage - But it seems none of the 3 reputable mechanics I've taken her to for servicing has ever changed them. God knows how old they are - I know the guy I bought it from had it sitting for 10 years - so they could be 15+ year old plugs.

Yes, they look lean, one complaint was very heavy fuel smell from exhaust, that's gone now, but maybe not for the right reasons, we'll see. - Thanks for the O-ring hint.

Colin, I'm not entirely sure tbh which setup has actually been fitted. From your description it is vacuum retard with a hose to the bottom of the back left carb, no I cant keep pressure on the hose, so looks like it needs a new vacuum module. Is it serviceable, can I just replace the diaphragm? So do I have a mutant under the hood?
is there a problem with them, or is that ok to live with?

The dizzy thing looks like a can of worms where I'm going to end up questioning whether I repair/service this or start looking at different setups. I'm sure there are plenty of eye gouging threads on that, which will leave me with more questions than I started with.

I get no misfires - so the cocktail of leads are fine

[lowact]

Looks like u have the SNGB vacuum retard version with maybe a faulty vacuum module. You can’t replace just the diaphragm, need to replace the whole vacuum module. Before u do this:
1. Check by hand that yr pick-up sensor is able to move, is not stuck (as per previous post). It should move freely about 20 degrees anticlockwise and snap back (via spring) when you let go. If it doesn't (likely considering the apparent condition), and wd40 doesn't help, need to dismantle/clean the distributor.
2. If there is free movement and you cannot hold vacuum, double check that it is the vacuum module and not a hose/connection that is leaking. To remove the module there is a small cotter pin to drive out, using a pin punch or the filed-flat nail …

Fyi, some maybe interesting info:

V12Es had vacuum retard, for better starting and idle. This was the Lucas Opus system. E-types never had vacuum advance, advance was introduced with the HE V12s, more than a decade after the last of the e’s. This was the Lucas CEI system. Vacuum advance enables better efficiency (fuel economy) and less heat. And the Lucas CEI system was more reliable; even today there is not a better distributor type ignition system (imo).

Retrofitting a vacuum advance system was a popular mod for v12e’s, whenever the impact on starting and idle was considered negligible or tolerable for the benefits (economy, reduced heat, reliability). Requires changing the vacuum tapping point.

Throttle plates, as they open, swing outwards at the top and inwards at the bottom.
For vacuum retarding ignition systems the tapping point is just inside the bottom edge of the throttle plate. When the throttle is closed the tapping is providing manifold vacuum. As the throttle opens the bottom edge swings inwards over the tapping point which is then relatively outside of the throttle plate where there is negligible vacuum, I.e. vacuum retard only occurs when idling, not when driving (except for a bit as it transitions).
For vacuum advancing ignition systems it is opposite; the tapping point is just outside the top edge of the throttle plate. When the throttle plate is closed the tapping point is effectively in the air cleaner providing ~atmospheric pressure, i.e. there is no vacuum at idle. As the throttle opens the top edge swings outwards over the tapping point which is then relatively inside the manifold providing manifold vacuum. I.e. vacuum advance only occurs when driving, not when idling (so that the start/idling impact is lessened).

SNGB replacement ignitions are Lucas CEI type for performance and reliability. There are two versions, the vacuum retarding-at-idle type and the vacuum advancing type. For the latter the part no. has an “F” tacked onto the end.

The distributor rotor turns anticlockwise. To advance the ignition the pick-up sensor must be rotated clockwise, to retard the ignition it must be rotated anticlockwise. The vacuum module pulls the pick-up sensor in the direction of the vacuum hose connection, so for vacuum advance the hose connection on the vacuum module points to the rear of the car, for vacuum retarding-at-idle it points to the front of the car. You cannot change distributor advance/retard function by just swapping modules, its a whole distributor thing.

The clear plastic cover in yr CEI distributor is there to protect the electronics from any arching between the rotor and the terminals. On it there is an embossed radial line pointing approximately towards the front left headlight. This is the alignment that the rotor must have when 1A cylinder is at top dead centre. There are 14 helical teeth on the distributor gear, 360/14 = 26 degrees, i.e just one tooth out of position is very obvious.

26 distributor degrees = 52 crankshaft degrees.

[jfmassa]

Excellent write-up! Your 2 posts clears the fog on an often confusing topic!
regards,
Joe

[JoeLondon]

Retrofitting a vacuum advance system was a popular mod for v12e’s, whenever the impact on starting and idle was considered negligible or tolerable for the benefits (economy, reduced heat, reliability). Requires changing the vacuum tapping point.

My friend that also owns a V12 e had often mentioned I should setup the advance system, he's also in central London and it works well for him. All the benefits you mention are at the top of my list. I do enjoy the nice starting I get from mine at the moment, but these other characteristics are more important for me, and since I'm here I might as well keep tugging on this string

This is something easy to do, or does it need handing off to a 'pro' ? I recall reading previously across a number of threads about drilling holes in carbs, and someone found a jig for precise drill location etc, I asked my buddy and he mentioned his were already there, but he has SUs, I'm running Strombergs.

I need enough hours of daylight and no rain, together at the same time, in autumn, in England, whilst working a six day week, to go through the other stuff you mentioned.

As per Joe... incredibly helpful reply, greatly appreciated.

[lowact]

Maybe you and yr friend could drive yr cars drive to Dundee and back, compare fuel use, then decide if it might be worth it; you might have to offer to pay their petrol …

I recall UK advertisements offering to add the req’d tapping point to strombergs, might have been Burlens, don’t have this luxury in Aus., If u want to do it yourself u need a drill press with a tilting bed and some vernier calipers:


Alternatively, some people don’t bother with a throttle edge tapping, they just use any available plain manifold tapping point and say starting and idle is nevertheless fine. Imo it would be a good 1st step, if it works well enough live happily ever after. If not, then think about modifying yr carb.

Converting yr distributor to vacuum advance: I have never had opportunity to dismantle an SNGB mutated distributor so I cannot say with certainty what is involved, others may know. I imagine it involves the vacuum module and the pick-up sensor carrier. The vacuum module would need to be changed. The sensor carrier may also need to be changed or it may be cleverly designed to just require repositioning. Trouble is the sensor carrier does not have a part number; it is sold as an integral part of the distributor. I suspect SNGB would not be able to do anything other than sell you an exchange distributor.

2nd hand advancing distributor could be an option for some; things to check: Does the vacuum module work (hold suction)? Is the (plastic) sensor carrier in good condition, not brittle or cracked? Is the shaft seal working, test this latter by blowing into the vent hole that is halfway along the distributor shaft, if u can the seal is nbg, oem is nla, the distributor has to be machined to enable a modern sealed bearing, cheaper to buy a new one …

[JoeLondon]

Hence I'm considering the switch over, as Im in for a new vacuum unit anyway..

So far, the 'aint broke" rule is working. I've replaced plugs and leads and I have managed to restore the pinking under strong acceleration that I had cured by tuning the old setup

[JoeLondon]

Update. I readjusted plug gaps and the pinking is sorted. I had left them a little bit wide, as that's what the previous ones were, but nipping them down to the 25thou solved the pinking. I'm yet to tackle the vacuum conundrum. I've read the monster thread here in the forum. manifold Vs ported, I wondered why there is not more chat about the microswitch thingamajig suggestion, sounds like the best of both? I've seen a Stromberg available online that already has a port, perhaps from a triumph? but also aware these things are setup as pairs. I can turn a bolt as well as the next guy, but I'm well outside my knowledge for the finer workings and implications of altering parts of this system. I'd like to decide before spending money on changing the vacuum unit.

A wealth of articles online about reading plugs, from what I gather mine look hot due to the almost the entire electrode colour, I would have thought also lean, but there is a clean dark layer all the way round the base ring. No splattering. On balance I think they're ok, again, running fine. (At least, no worse than before, but could be better).

[JoeLondon]

[MarekH]

...but also aware these things are setup as pairs.

You only need one port to get a vacuum signal for your distributor. The reason they got used in pairs was because the port was not used for its vacuum signal, but rather as where exhaust gas recirculation was fed back into the input.

I wondered why there is not more chat about the microswitch thingamajig suggestion.

It's from a XJS or XJ12, so most people on this list would likely be unaware of its existence, whereas Philip Lochner is very familiar with the later fuel injected v12s as he has converted several to be run by Megasquirt.

kind regards
Marek

[JoeLondon]

It's from a XJS or XJ12, so most people on this list would likely be unaware of its existence, whereas Philip Lochner is very familiar with the later fuel injected v12s as he has converted several to be run by Megasquirt.

Thank you Marek. I think it's time I took the car to someone who knows what they're doing. I have too many questions. What setup I have, which one to fit, why the exhaust smells rich but the plugs look lean, is the timing correct, are the carbs tuned properly. I'm looking to improve one part of the system when I have doubts about the rest. Someone savvy would take one look and a sniff and say I need to do xyz. I just need to find someone not incredibly far away that knows this engine like the back of their hand. She runs well enough, but I'm sure there are some lazy horses sitting in that engine and I bet it could run better still.

Chipping away at the list where i can.. New rear hatch weatherstrip fitted (since found the actual source of ingress was probably the antenna hole), NOT going to replace the rear window seal - last thing I need is to not be able to get that back in when I don't have cover! Door drains sorted, vapour barrier behind door cards (somehow sure I'll still have wet floors next rain), I've stripped and fixed the clock which weirdly gives more joy than I expected. Found the source of the incredible cabin fuel smell was the fibre washers on the rebuilt fuel pump which, after reading need to be much tighter than I thought, are now bone dry. ...while my banjo gently weeps..

I'll be digging around the IRS at some point, needs new rear shocks, springs, brakes.