DCOE equipped E-Type popping and farting excessively

[ianc9]

I recently bought a restored '68 E-Type S1.5 2+2 US sourced LHD. the PO did a full restoration including a full engine rebuild which included a swap of the Strombergs to DCOEs.

The car runs well when pushed but on idle and on trailing throttle it pops and farts excessively. Bad enough to make me not want to drive it anywhere that's built up (and I'm not a shy kinda guy )

Apparently the carbs were set up on a rolling road and that gave a poor result (The PO did say what was wrong but I can't recall). He then took it to another place and they did some tuning to get it to current state.
There is a set of jets etc. with the car which were replaced at some stage during this tuning process.

So I've done a little investigating.
1) Plugs - Some show it running a little rich (1,2,3), Some a bit too rich but not terrible (4,5) and 6 was caked with soot (counting cylinder 1 at bulkhead).
2) When in idle I could hear the motor stumbling (missing) pretty regularly.
3) I put clean plugs in and pulled the leads off one by one. All made the motor stumble as expected except C6. With it disconnected there was hardly any change.
4) checked sparks including swapping leads. All good. There is some sort of electronic ignition on the car.
5) The idle mix screws are set as follows in order of 1-6: 2.2, 2.2, 1.3, 1.0, 2.2, 1.5
6) I tried closing the C6 idle by a full turn and it made no obvious difference


So my suspicions:
1) Is there something going on with just one carb barrel which is making that cylinder run so rich its not firing properly on idle
2) Do I have an exhaust valve clearance so tight its letting the charge drop into the exhaust on compression stroke?

Have I missed anything obvious?

My next step. (I'm currently in France and away from all my tools in Ireland)
I've Amazon's a set of feeler gauges and a compression tester to diagnose valve/cylinder issues

Anything further I should be looking at?

[christopher storey]

Ian : there are all sorts of hidden pitfalls with DCOEs . One common one is that people do up the securing nuts tight, so that the intended flexible mounting of each carburetter is absent.( You should be able to move them perceptibly up and down on the mounting) . This leads to frothing of the fuel in the float chamber which in turn leads to a number of difficulties, one of which is that the float level may become erratic and unreliable , and this in turn can affect the operation of the emulsion tube(s) which in my experience are absolutely critical to proper functioning of DCOEs . Another problem, especially if you are already getting spitting back, is that when the carbs are properly flexibly mounted, a spit back can blow the O ring between manifold and carb out of its seating , thus creating an air leak, which leads to further spitting back......

I would check for displaced - or broken - O rings here and now - it only requires one spanner to loosen the fixing nuts on the carbs . When you get home, I would take the filters and lids off all 3 carbs and identify the precise setup you have got. The first very important one is the choke size - as so often the inexperienced think that the bigger the better, but in my experience for a road car 36 at the very most ( and probably 34 ) is needed for low and mid-speed tractability. The bigger you go the worse the slow and light throttle running will be. Then identify what emulsion tubes are in ( F9 or F16 probably are the preferred ones ) and what idle / main/air corrector etc jets are in, together with pump jet size etc . Check that all 3 carbs are the same!!! If you then post your complete specs, someone on here will almost certainly be able to give you an idea of what may be amiss

Another problem with DCOEs is that some setups miss out the vacuum advance. On a race car that does not matter, but on a road car it can turn it into the very sort of part-throttle pig you describe

I would advise anyone running DCOEs to seek out the wonderful books ( IIRC there are 3 in all but the one on tuning is the vital one ) by the late John Passini on the setup and tuning of these carbs. They are a mine of useful information not readily available elsewhere, and although I think they are now out of print you should be able to find S/H copies on the net - edit or even new ones

PS I agree absolutely that the first thing to do is check compressions

[Heuer]

From the Forum Knowledge Base:

Weber Set up Guide 1: https://www.dropbox.com/s/h8983mm6qxa3s ... E.pdf?dl=1
Weber Set up Guide 2: https://www.dropbox.com/s/7zhzctlaawjvq ... m.pdf?dl=1
Tuning DCOE Carburettors by Kimble & Trindal: https://www.dropbox.com/s/4hj5d08yxoi0b ... r.pdf?dl=1

[abowie]

I would advise anyone running DCOEs to seek out the wonderful books ( IIRC there are 3 in all but the one on tuning is the vital one ) by the late John Passini on the setup and tuning of these carbs. They are a mine of useful information not readily available elsewhere, and although I think they are now out of print you should be able to find S/H copies on the net - edit or even new ones

Excellent recommendation Christopher!

The first two books were printed in 1973 and are expensive and hard to get 2nd hand but the tuning book was reprinted in 2008 and is avaialble.

Best price is from the Book Depository
https://www.bookdepository.com/Weber-Ca ... 1855207592

[Series1 Stu]

Excellent recommendation Christopher!

The first two books were printed in 1973 and are expensive and hard to get 2nd hand but the tuning book was reprinted in 2008 and is avaialble.

I'd forgotten about these, we had them years ago when we used to play with Cortinas and Capris. They probably went with my 110 bhp 100E Popular when I sold it in 1987.

I just ordered all 3 from Amazon - the first 2 second hand, the 3rd is new. Prices were reasonable.

Regards

[gtjoey]

I think the majority of your issue is IGNITION.
What is it?
What spark plug wires and coil, miss match ignition makes EVERYTHING else go south.
Not saying webers are perfect but the either close or open.
Would like to see what ignition you have....Good luck
gtjoey1314

[ianc9]

Compression results when cold . First dry and second with teaspoon of oil down the plug hole
C1 155, 160
C2 90, 95
C3 120, 120
C4 100, 100
C5 90, 90
C6 80, 85

I think this is telling me I have leaking valves
Which means clearance way too tight, sticking valves or burnt seats?

[gtjoey]

Maybe , BUT IF YOUR NOT FIRING RIGHT FOR A long time YOU LOADED UP THE CYLINDERS AND VALVES
Sorry for the caps, hit the wrong button
For GTJOEY, what ignition is in the car?

[tim wood]

I’ve got both books by John Passini . Will have to dig them out if you’re (or anyone) interested

Tim

[christopher storey]

Ian : the 5 and 6 both being low suggest the possibility ( but not more than that ) of a blown gasket between cylinders . But of course it could be valve problems on both, and that certainly applies to 2. However, since you are so far from home, workshop, tools etc, and since you obviously got down into France without e g overheating which would be expected with serious gasket problems, i should drive, gently ish , back home and then top overhaul it from there. Perhaps for safety's sake, if you are anxious about it , before doing that you could check the valve clearances which again does not require much in the way of tools to do

PS the fact that oil makes no difference suggests there is nothing wrong with the rings. Incidentally, I have no idea what LOADED UP THE CYLINDERS AND RINGS means, if anything

[Mich7920]

Hi Ian,
If you 'r not far from Poitiers( 86 ) or Niort ( 79 ), I can gladly lend you my workshop with all the tools for E Type.
Regards
Mich

[gtjoey]

It means LOADING FUEL AND WASHING DOWN the cylinders and vavles if its not firing correctly.
9 out of 10 fuel issues are ignition.
Are you running points?
Petronix?
1 2 3 ?
GTJOEY1314

[ianc9]

Apologies All for slow response, I've house guests AND my Internet has gone down!


Update.
I re-did the compression test while holding the throttle bodies fully open (duh!) And the results were very positively different.
All at 175psi give or take 5%.
I also checked the valve clearances and all were either within tolerance of slightly wider. None more than 2 tho wider than spec.

The ignition system is 123 and apparently its on "7" setting ( according to PO - I don't know how to check)

So I'm back to the carbs and/or ignition.
The carb jet setup is
Main 145
Emulsion tube F18 or F16
Idle jet F9 55

I only got a chance to check them in one carb due to pressure from the boss due the house guests!

[ianc9]

Hi Ian,
If you 'r not far from Poitiers( 86 ) or Niort ( 79 ), I can gladly lend you my workshop with all the tools for E Type.
Regards
Mich

Mich
I really appreciate this offer. I'm currently 30mins South of Angouleme so within range.
I have to go back to Ireland for a couple of weeks, but could I contact you when I get back over?

Ian

[Mich7920]

Pm send
Mich

[gtjoey]

Good start...
Well the 123 is the best.
Pull a spark plug wire and lok at the center , is it BLACK or COPPER ?
What coil and I hope there is no ballast resistor, that will cut your voltage from 12 to 9 when hot!
Hence , fart, load backfire........set plugs around 30/32

[ianc9]

I'm back in Ireland and the car's still in France so my ability to do tests and make changes is somewhat limited :). But I'm thinking through what I need when I get back and what tests I should be doing. This has prompted a few questions I hope ye can help me with

Keeping in mind that he primary problems are:
- Excessive fuel being burned in the exhaust causing loud popping on idle and particularly on overrun (bad enough that I cringe going through a town)
- Rough idle which gets worse when you pull any of the spark leads off except cylinder 6 (closest to radiator)

Plugs show rich running with C6 particularly caked and smelling of fuel
Compression test was good across all cylinders 175psi +- 5%
Valve gaps also good across all inlet and outlet
decent spark visible at all cylinders. Swapped leads around but this cause no change in behaviour
Car pulls well without missing on medium to wider throttle openings

The 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?

More Q's to follow :)

[Heuer]

if you have electronic ignition the first thing you need to change are the plugs for resistor versions = NGK BPR5ES. When I installed the Megajolt ignition I was plagued by misfires using NGK BP5 plugs. Swapping to NGK BPR5 cured the problem. It was RFI that was screwing up the electronics.



"At the moment the spark jumps the gap it causes a high frequency burst of energy, this is known as RFI (radio frequency interference). This is why resistor spark plugs were introduced in the mid 1960's. Placing a resistor within the spark plug suppresses the RFI. Without resistor plugs in your car you can experience static on your radio as well as interference with other sensitive electronic equipment. Some later model vehicles as well as newer Powersport engines must use resistor plugs for a proper "talkback" to the electronic ignition. As a rule, performance is in no way impaired by resistor spark plugs."

[gtjoey]

THERE YOU GOOOOOO.
1,You cant run OLD COPPER SPARK PLUG WIRES with an electronic dizzy.
The copper core wire will create a static or impulse feed back as they heat up creating a SPIKE to the unit.
PLEASE ,Ive been down this road ,Go 7mm or8mm carbon or fiber core NON copper wires which are in any modern car .They are at any autoparts store or Rob Beere makes the wooden dtype holder and the wires complete for around 300 dollars or just make your own.
Your losing spark.
Yes the webbers dump fuel but start there and gap the ngk plugs to 30/32ish
2 No ballast resistor in ANY WAY,IN LINE OR IN COIL!
3. start with a 3.0 coil nothing crazy, bosch blue or petrnix. Some say 1.5 for more spark but start with 3,0mn
summary......3.0 coil , new ngk plugs gap30/32 7mm or 8mm wires NON COPPER, Ibet all your troubles go away......minus the rich mixture....
The popping is the load feeding back to the dizzy........when hot!
Its all resistance.......
Set you advance at number 2 if your car has stock cams.
Good luck.......

[ianc9]

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