Advice sought: Fuelling and ignition upgrade options.

dj_efk

dj_efk

Well-Known Member
Messages
599
Reaction score
84
Location
South-West UK
Hello all, opinions please:

I am at a possible crossroads with it's fuelling and ignition system - I could spend the money fixing the standard ignition and fuel system components, or I could spend a bit more and upgrade these areas.

My Primary question is: what are the options on how best to upgrade whilst keeping the original engine in place?

I realise there will be more than one option, let me try and give as much info as I can on what I'm faced with currently:

1) The distibutor was "modified" by the previous owner to allow running on standard 95 RON unleaded fuel when leaded "four star" 98 RON was phased out here in the U.K. (blobs of weld on the base plate to reduce the amount of ignition advance!). This needs grinding off. It could be that actually what he has done has caused the distributor (or parts of it) to be scrap, so new or used parts may be needed. Potential spend needed could be up to £100 to £150 for a good used distributor (eBay prices I've had pop up occasionally), assuming I can get one that's matched to my engine. A point that may be relevant to note is the cam is reputedly slightly updated from stock, the dizzy advance curve is not.

2) The twin Zenith Inat 35/40 twin-choke carburettors need a full rebuild and setting up correctly, this is within the realms of my capabilities but in reality I doubt I would have time and it would be expensive to do properly (I'd want to get all the components ultrasonically cleaned, plus I'd need a specialist, all told I'm sure I'm looking at least £400 for the rebuild and then another £100 minimum to set them up).

3) The engine was rebuilt around 40k miles ago and is fundamentally strong (checked compressions and has good oil pressure), although due to the above is out of tune. Currently I'm getting under 20mpg and although it's a quick car I'm sure a fair few of the claimed 170 horses are relaxing in their stables!


I would have to spend minimum £500 - 600+ anyway to get the thing working as per original spec, therefore, assuming that done well this is one of those areas you can deviate from standard and make the car more attractive to buyers should I wish to sell, I'd be happy to spend a bit more on an upgrade.

Could someone with experience lay out some options and what the compononents needed would be (along with cost estimates of these plus how long it would take someone who knows what they're doing to execute)?

My aims with any upgrade are:

- Keep the original engine: It is sentimentally attached to the car because the previous owner rebuilt it and somehow it doesn't seem right to change it. I believe I don't need to do so to upgrade to EFI?
- Budget of under £1000 all-in and the parts needed are fairly readily available - this rules out transplating a later E9 injection system
- Reliability / The thing doesn't need tinkering with once installed
- Improved fuel economy and hopefully some extra ponies


Related to this: can you drill and tap a cast iron exhaust manifold for a lambda sensor? The standard item is meant to flow OK so if I don't have to replace that to go fully up to date then that's at least one hurdle out of the way for closed loop systems.

Thanks and appreciate all contributions. Have a few pics of the beast in question - It's a 1969 2800 CS - some of you may recognise it from when I posted regularly a few years back.

David

IMG_0335_zpsitjgdg9j.jpg

IMG_0334_zpsghm6n3pj.jpg

DownloadafterTravelling-Feb2012522.jpg
 
A stock coupe with Zeniths returns 13mpg (US), I never got more than 20 and that is freeway cruising at 70-75 only. O2 sensor would be added to the down pipe not the manifold. Sounds like the 1/2/3 Ignition discussed here would be a good addition. BTW, beautiful coupe!
 
Clearly.

In answer to your question, that's what I'm putting to the floor here - what's the best compromise between cost (£1000-ish budget including any refurb work) and time to install - I'd quite like it if some folks here with experience of upgrading to EFI could chime in with their thoughts.
 
You could always install a triple webber setup to get a smooth running engine alongside the 123 ignition distributor. You would wake the engine up some. I would stay away from any fuel injected systems. You could always put the stock Zenith carbs back on whenever needed for the sake of originality.
 
Budget-wise I'm afraid that's likely to be totally out of the question. Also my driving style is not conducive to such a setup, i.e. I tend to take it easy and let the torque do the work when cruising!
 
If that is your budget then fix what you have got. The £1,000 won't even get you the EFI parts. The ECU alone would be $500-$1,000, plus EFI intake manifold parts, O2 sensor ($100), welding, toothed wheel, injectors ($250+), return fuel line, fuel rail, fuel pump/sender ($250+), wiring, and then the labor and labor of tuning to your specific engine. I would say easily over $5k to have someone do this for you.

Now if you could find some cheap used D-jet parts clean them up and install them yourself then just maybe... too optimistic?
 
Sven said:
Now if you could find some cheap used D-jet parts clean them up and install them yourself then just maybe... too optimistic?
Click to expand...

There is a parts CSI on the market at the moment (see the parts section). I would reach out to the seller/buyer asap to snatch those parts up now. :)
 
David: Your car is beautiful but the steering wheel is on the wrong side - or did you flip the picture to see if anyone would notice? j/k...

Triple webers would be beyond budget but a pair of Weber 32/36 carbs might be manageable, possibly with a "synch link" to convert from progressive opening throttles to simultaneous (or whatever it's called when both throttle plates open together). Those wouldn't require special manifolds, and the stock air cleaner can be adapted to fit. Another option may be Weber 38/38's although these won't help your gas mileage. It seems that coupes never get decent gas mileage unless either endlessly fiddled with or fitted with programmable EFI.

As above, I think careful attention to what you have is your best way forward.

Question: I see you have wood across the dash (some call it the grab handle), but I thought this only occurred on the 2000C or 2000CS models. Was this an option on the 3.0CS or how did this happen?
 
First of all, on your budget changing to fuel injection is out of the question.

I have a set of triple Webers in my car, along with a 123 distributor, but my driving needs are much different than yours.

I had a set of Weber DGAVs on the car when I bought it, but I recommend rebuilding the zenith carburetors, doing as much of the work as you can yourself. This will be the most economical way to get them rebuilt (assuming you are cautious and don't make any huge mistakes). The initial setup should not be difficult; there should be OEM reference material that indicate how to do the initial setup. From there you can pay someone to do the fine tuning.

As to the distributor, given that you state that your car is designed to run on a stock distributor curve, I would source a used stock distributor. Alan stated above he has one. Given your description, I would not try to fix the one you have.
 
I rebuilt my Zeniths and didn't find it too hard. I had a little trouble getting one section apart, but the gasket kit wasn't expensive. I didn't change the jets as my engine is stock. The leather accelerator pumps had to go. I did have an issue with the gasket for the float bowl, apparently it was a bit on the small side and would hang up the float so it wouldn't rise up to shut off the fuel flow, resulting in gas pouring out of the air cleaner.

I replaced the points in my stock distributor with a Pertronix and that made a huge difference, but the timing was still not very stable so I looked for and managed to find a rebuilt distributor. The parts needed to rebuild distributors are getting scarce, so the 123 distributor may be our best option going forward if a good used one can't be found.

Ian
 
Guys, thanks for all replies - appreciated. I had not realised that using BMW parts of a later model would not be low-cost.

For fuelling - Taking the common theme of advice, if I'm not being realistic with budget then perhaps the best thing to do is spend the cash on a home rebuild of the Zeniths then (Dequincey has already PM'd me with offers of support and tutorials - his opinion is that can still be expensive if they need more than just cleaning + diaphragms and gaskets replacing mind).

Ignition-wise - As my cam is a little spicier than stock then perhaps I should look more closely at the Bluetooth / TUNE version of the 123 distributor. I see a few guys on here report similar results with that as what I'd expect to see using megajolt or similar distributorless systems. Are there are before / after comparisons of performance anywhere? I tried to search but the forum search function thinks the term "123" is too short!

Does this distributor come with stock advance curve maps to start out from? I guess the only way to then end up with a map that is exactly matched to my particular engine and UK fuel is to go to a competent rolling road / dyno shop, correct?
 
Last edited:
I am still working on my timing, but I began with a curve Stevehose sent to me. He is much farther down the path with his setup, and I believe I still have his original curve. We both have 3.0 versions of the engine, but you are welcome to my initial curve if you like.

One difference in our curves; I am using manifold vacuum, whereas Stevehose is using ported vacuum for vacuum advance.
 
Rebuild your carbs... its not hard and it's not necessary to ultrasonic clean them; standard carb cleaning solutions work fine. Do one at a time so you can refer to the second if you get stuck. Take lots of pics during tear down.

Lots of carb guys here can help...
image.jpeg


:)


Get the 123Ignition... you won't regret it. Lots of users here to help with plotting a curve to get the best out of your performance cam.

Ed Z

BTW... GORGEOUS car... wow
 
Last edited:
You must log in or register to reply here.
Back
Top