DCOE equipped E-Type popping and farting excessively

[Heuer]

So if I'm using those leads do I still use "R" spark plugs?

Yes! I had carbon leads on my car but the car still misfired with standard plugs. They are less than £3 each so why would you not fit them?

[ianc9]

Yes! They are less than £3 each so why would you not fit them.

I'm asking because I'm unclear if you should use both resistive plugs and resistive leads in the same circuit
I can stretch to the £3

[Heuer]

Yes, you can use both together. It stops interference from the leads and at the plugs where most of the RFI originates anyway.

[gtjoey]

So I'm pretty sure the leads are from Rob Beere. At least that's the name on the separator and I have an invoice from 2020 from the PO showing Leads and Separator.
So if I'm using those leads do I still use "R" spark plugs?
The coil is this one
https://www.sngbarratt.com/English(US)/ ... 0dlb105%60

Yes as Heuer has said.
Interference and resistance, everything effects the unit.
You can tell if the wires are correct just pull one off a plug.
Look down the center of the wire, it might be a black, blue or clear rope cord looking thing.
Those are all good.
Just no copper.
Good luck.
gtjoey1314
ps 10tdc for timing is important to start, just breathing on the 123 dizzy will be a huge 4 degrees change.
They are very very accurate.

[ianc9]

Thanks both for the help on Spark plug and Leads questions


1) The car is currently fitted with NGK BP5ES plugs - OK or should I be considering something different? When I had fouling plugs in my old Alfa Gulietta (with DCOEs) I fitted Lodge plugs and it helped
2) As far as I can tell there in no fuel pressure regulator fitted and I recall the Alfa did have one. Should I need one?
3) Was considering going with solid core spark leads to improve spark. Would this be ok with 123 ignition or will it be upset with the RFI?
4) When I initially ran the compression test I forgot to open the throttle. Doh! . But I don't understand why the closed throttles didn't just give a consistently lower reading across the cylinders. The readings varied widely. Can anyone explain why?

Anyone have views on the whether a Pressure regulator should be fitted and also why I didn't get consistently lower results with the throttle closed?

[bitsobrits]

1. Believe you want an R in the plug number (R for resistor) i.e. BPR5ES

2. If you are using the stock SU pump a regulator may not be required, but wouldn't hurt. DCOEs are wanting 2-4psi to be happy.

3. NO to solid core wires with a 123 distributor. Solid core wire is simply not needed for a street car running with good quality (non solid core) plug wires.

4. Can't explain why but have seen that myself. Just redo the compression checks.

[DWW]

Anyone have views on the whether a Pressure regulator should be fitted and also why I didn't get consistently lower results with the throttle closed?

The throttle is in the idle position thus not completely closed so there is enough air in the cylinder to compress and by the time the compression stroke is reached both valves are already closed so the throttle open or closed is out of the equation.

Hope that answers your question.

[gtjoey]

Don’t mix things up here.
You need carbon wires and resistor plugs with the 123
The car will idle like a flat head Merc.
I explained the coil already
Usually I run an online fuel pressure gage with Webbers.
And an adjustable inline fuel pump
The stock SU is a stretch aT only 2 to 4 pounds imho
Start with ignition
Then timing
Your was a 68
Make sure ALL resistance such as a block or in coupe resistor is gone!
Good luck
Gtjoey

[Heuer]

The SU pump is rated at 3.8psi but it pulses at 6psi! Suggest you fit a Filter King and set to 2psi; details here: http://forum.etypeuk.com/viewtopic.php?p=711#p711

[ianc9]

Thanks David
I'll source one of those.

[ianc9]

Hi all,
The car is now home in Ireland and still running poorly. Since I last posted I've done the following:
Fitted fuel pressure regulator.
No noticeable change but good peace of mind that fuel pressure is eliminated
Stripped the jets etc from the carbs (in situ) and cleaned them out
No change. The big imbalance in the state of the plugs was still evident
Swapped carb locations.
C1 stayed too lean (reading plug colour) but there was some variability across other plugs after the moves.
Checked compression again (just in case!)
All cylinders still reading 170psi +/- <5%.
Diagnosed a leak in the brake vacuum system causing Cylinder 1 run very weak (Fixed)
Unsurprisingly the idle became much smoother But in all the changes I'd somehow introduced a bad misfire at cruising speed.

Sent it to a carb specialist here in Ireland who I'd hoped had the equipment and knowledge to get to the bottom of this.
Turns out their rolling road has been dead for some time - so not as equipped as I'd expected.
Anyway their findings so far are:
- Compression was all over the place across the cylinders - until they tested again with the throttles fully open!!!!. This did not fill me with confidence.
- Hydrocarbons >2000ppm at idle on one bank (of 3) and 500 on other. They tell me changing the (already new ) plugs got this to 900 and 500.
- CO2 at 3000rpm (without load) was 9%! and that's with 1.45 main jets. But worth noting that there are 32mm chokes in the car (put in when the PO brought it to a reputable tuning establishment in UK).
- They put 1.35 main jets in at this took the CO2@3000 to about 5% - still very high.
- They also say they've put it on an oscilloscope and that the spark is "perfect" and the problem must be "somewhere other than the carbs and spark".
I'm not fully confident in this diagnosis (and do feel I need someone else to validate it - see Qs below)

But if I take it at face value then that leaves the top end of the motor. Right?
And I think that means taking the head off.

Before I do that I have a few Qs for this community
- I have 170psi compression and <5% variation (tested cold and also hot)
- Cam timing has been checked and is good
- Valve clearances are all at or very slightly greater than recommendations (4th inlet and 6 outlet)
- I have no bubbles in my cooling system

The Questions
Is it possible to have a sticking valve or other top end issue given the diagnosis and results already undertaken?
Is there any further top end diagnosis I can do before pulling the head off?
and the Long shot question
Does anyone know of a good specialist in Ireland?

[abowie]

Just some thoughts as I read your post.

Regulator. Good idea, but obviously not the problem.

Cleaning jets. Ditto.

Carb swap. "Reading" plugs with non leaded fuel is essentially useless.

Compression. If you get 170 psi on all cylinders, then the valves are fine.

Vac leak fixed. Good

If they don't have a rolling road they're wasting your time. Find someone else.

Hydrocarbons all over the place just confirms that your webers are not set up correctly.

Oscilloscope/ spark. Yes your problem is Weber tune, not spark.

Your Q's

I don't think you have a valve problem if you have 170 psi on all cylinders.

I think at this stage you need to be sure your carbs are set properly before you would consider pulling your head off.

[christopher storey]

Your excessive CO is not wholly dependent on main jet size - the air correctors will also have an influence . Before you do anything else, get the Passini tuning book and study it thoroughly - this means not just half an hour but a couple of weeks ! This will give you an understanding of how every setting on a DCOE has a degree of inter-dependence on other settings, and this particularly applies where you alter a main jet setting - at a guess ( and that's all it is) you also need to use bigger air correctors - your aim running light at say 2000 rpm should be CO of no more than 1% and possibly even lower

[ianc9]

I think at this stage you need to be sure your carbs are set properly before you would consider pulling your head off.

That's where my head is too.
But at this stage I think I need a good specialist who has enough of the right equipment in order to troubleshoot the carbs.

[ianc9]

Your excessive CO is not wholly dependent on main jet size - the air correctors will also have an influence . Before you do anything else, get the Passini tuning book and study it thoroughly - this means not just half an hour but a couple of weeks ! This will give you an understanding of how every setting on a DCOE has a degree of inter-dependence on other settings, and this particularly applies where you alter a main jet setting - at a guess ( and that's all it is) you also need to use bigger air correctors - your aim running light at say 2000 rpm should be CO of no more than 1% and possibly even lower

Thanks Christopher
FYI - The air correctors are already pretty big a 200

I understand there is a huge interdependence across the adjustments in a DCOE. In addition to the Passini book I think I'd need access to different sized idle, main, accelerator jets, chokes etc. plus an exhaust analyser and ideally a rolling road

So as I mentioned above - I think I need a specialist who knows Webers with the XK.

[Tom W]

Have you checked the basics are correct before pulling the engine apart or spending more money at a specialist?

Float levels. Are they equal and at the correct height? They don’t necessarily come set right out of the box, and in my experience specialists don’t always check the basics before diving in and changing things.

Ignition timing. Is the distributor in good condition? Does it have an appropriate advance curve for Webers? Is the timing set correctly?

Air leaks between the carb and manifold. It’s very tricky to get the carbs mounted tightly enough so they don’t leak, but not so tight that they have no movement.

Carb balance. Are they balanced correctly, not just at idle, but throughout the range of opening?

Getting the above points sorted has made a much bigger difference to the running of my car than anything else I’ve done on the Webers.

[ianc9]

Have you checked the basics are correct before pulling the engine apart or spending more money at a specialist?

Float levels. Are they equal and at the correct height? They don’t necessarily come set right out of the box, and in my experience specialists don’t always check the basics before diving in and changing things.

Ignition timing. Is the distributor in good condition? Does it have an appropriate advance curve for Webers? Is the timing set correctly?

Air leaks between the carb and manifold. It’s very tricky to get the carbs mounted tightly enough so they don’t leak, but not so tight that they have no movement.

Carb balance. Are they balanced correctly, not just at idle, but throughout the range of opening?

Getting the above points sorted has made a much bigger difference to the running of my car than anything else I’ve done on the Webers.

Thanks Tom.
All of the points you mention regarding the carbs have been checked and are good.

The points on the ignition is trickier. Determining what's "appropriate" for Webers is not straightforward. I'm running a 123 distributer using the "7" map and 10 degree static advance. I have tried reducing the advance in stages back to about 3d without improvements.

This is the specific 123 installed https://www.sngbarratt.com/English/#/FR ... 0%60123%60

[Tom W]

Engines fitted with Webers can benefit from more advance at lower rpms, but the maximum total advance should remain the same.

How much is best determined on a rolling road or engine dyno. Whether the correct curve can be achieved with the pre-programmed 123 is another matter.

[ianc9]

Whether the correct curve can be achieved with the pre-programmed 123 is another matter.

Ah but before you can say that you first have to determine what a correct looks like

[Tom W]

You can get closer to identify the correct advance curve with some experimentation. However, it does come with some risk that if you get it wrong and add too much you can damage the engine.

You have 16 curves to pick from, and can also move the static timing, so there is some scope for adjustment but the resolution between each step isn’t that fine.