Weber DCOE 40 151 Fuel Level

[marode]

"Personally I do it myself as there is a lack of experts and rolling roads where I live. So better to invest in a selection of jets and do it myself.

Absolutely! That's the point, couldn't agree more.

[Mike McHugh]

I have just read this whole thread, as me recently bought 65, much modified Elan (looks just like my first college autoX BRG), has the 40dcoe 151 Italian carbs.
Are they identical to the 18/31 type? Any difference in tuning?
Having stumbling off idle, and lack of power, but drove it home to Reno, over the Sierras.
Plugs good color but a bit wet, thinking of going leaner for the altitude 4,500 -6,000 ft.
Or putting in naked bp6 vs 7.

Just discovered cams are 150 hp, .40” lift
Some vintage racing history, fresh rebuild.
Looking for my Weber book that I haven’t seen for 30 years….
I remember the book’s conclusion on tuning…”Suck it and see”.

[mbell]

151 have different (better) progression hole positions, air balance screws and plastics floats. They seem to be well tuneable in twin cam in my experience.

Sounds like you need to check what jets etc you have and do a full from scratch setup on them.

[Mike McHugh]

Thanks, looks like more than carb tuning…the wet with gas plug has 0 intake valve clearance. The others valves have ok clearance…hope the engine builder just made a math blunder when adjusting. Here goes…

[mbell]

It's common, maybe even normal, for the valve clearances to cost up when the head of torqued down. So if they where set with head on the bench, I wouldn't be too concerned and just correct them.

[Hawksfield]

Hi
it happened to me QED did work on my head and set the clearances, when the head was torqued down I had to readjust a couple of them. The work by QED was top notch

Good luck

[The Cyclist]

Reviving this very useful post, I would like comments or suggestions on what I have done.

I have a very standard S3 Elan and after it's rebuild it has been very difficult to start after sitting for a few days and has had a noticeable stumble about 2000 rpm which I know is a transition zone.
After fitting an electric fuel pump made no difference I checked the float heights [I know I should have done this the other way round - sigh]. The manual says 8.5mm with brass floats - and they started about 10mm or more.Bringing them down to about 8.5mm seems to have really helped both issues, but now I'm worried I might run into problems running rich. The car has Lumenition ignition and I am running BP6ES plugs as I don't do long high rev runs.
Is there anything that will alert me to this apart from plug colour [which seems a bit unsubtle]?
Am I missing something?
Thank you in advance for your thoughts.

[andywatts]

I've seriously considered installing a lambda sensor. Ideally it would be installed in the Y-piece (requiring removal and welding in a boss), however some articles suggest that in a non-catalytic system it can be pushed up the tail pipe. The 'wideband' type would give a very good indication of mixture strength under different conditions. Power from the battery and bring wires into the car to a hand-held meter. However the faff is considerable for just a once-off measurement, and finding a rolling road seems a better option. Not so many of them around now though!

[alfadave]

Take it to Mikeanics in Congleton. Full rolling road facilities.
Recommended by CLOG people.

Mature, experienced guy. Knows his stuff.

[ericbushby]

Regarding the fuel level I prefer to measure the level directly rather than measuring the float height.
If you remove the jet cover and one main jet stack (the larger screw of the two) you can then see the fuel surface with a small torch.
Using a small diameter probe such as a cocktail stick, then with the torch you will see the surface shiver as the stick touches it. I use a vernier depth gauge for this because I have one but a mark on the stick is all you need.
I am using a distance of 29mm from the top of the float chamber or, easier to measure, 45mm from the rim of the jet cover.
The engine must have run just before measuring or some fuel will have evaporated.
I think this method may be described earlier in this thread but there is a lot to look through.
I am using BP5ES plugs as they seem to stay cleaner longer.
Best of luck
Eric in Burnley
1967 S3SE DHC

[mbell]

I also measure directly rather than via float level. As the actual level can be effected by various factors like float variance in weight etc.

I've recently lowed my fuel levels as been chasing rich mixture at cruise speeds aka 2.5krpm-3k rpm. I was running at 25mm from the top which was giving the rich running but have increased it to 27mm. This seems to have improved it in limited testing so far. My memory was that 27mm gave a around 8-9mm of clearance between float and lid at the far corner of the float.

I've fitted wide band AFR on my car thou so I can see the impact of my changes and try make informed changes to improve specific. The lambda sensor is fitted in the center pipe just under the gearbox.

Without that you just have to use the drive-ability and bit of knowledge to tune them, unless you want to take to a professional.

[The Cyclist]

I tried using the vernier method, but I couldn't reliably see the touch. After a week of standing I couldn't locate a level at all and initially after running the electric fuel pump I think it was about 31mm - which is why I checked the float height.
I considered a lambda/ air fuel gauge but it's a lot of faff indeed.
So far I am reassured, so I will try my friendly local old car garage with it's 73yr old mechanic and his Crypton tuner and see what he thinks. It's been suggested I need to advance the ignition beyond standard as I have lumenition - but that's off topic I know and I don't just want to leap in to that quite yet.

It should be nice tomorrow so I'll go for a long spin & see how it feels.

Thanks for the comments - unfortunately Congleton is 5 hours from here....

[ericbushby]

Hi Cyclist.
Can you see that you might get more focussed response if you told us where `here` is.
Eric in Burnley

[alan.barker]

Hi Andywatts,
I fitted a Lambda sensor on my TVR 3000S because the Engine had been modded and no rejetting in Carb. Costs for kit 220Euros cheaper than rolling road. Better than sticking a sensor up the Exhaust pipe. Possible to monitor while driving in real conditions. Possible to log on Laptop.
Once done put Blank in Lambda Boss. On other cars i can just add Lambdha boss.
Imho good investment.
Alan

[The Cyclist]

Hi Cyclist.
Can you see that you might get more focussed response if you told us where `here` is.
Eric in Burnley

Oh sorry, I thought it was in my sidebar. I’m in Bournemouth.