Twin carbs

[Sprint88qv]

And to confirm, my numbers were at c870 rpm.

Interesting to see if Dave’s were recorded at similar rpm.

[alfadave]

Yes mine is a 1.5 with 36's

First I got 2 on on carb and 3.5-4 on the other.

So,I didn't know whether to up the lower one, or reduce the higher one.

I upped the lower one and got all 4 at 3.5-4.

Tacho reading approx 900 rpm.

Come on Lou, tell us whats what!

[Sprint88qv]

Yes, we’re all on edge here

[alfadave]

I should have read the instructions for the Air flow meter!

It says 1.8-2.5 for Weber carbs is the "experienced" figure

[Sprint88qv]

Ah, now that’s interesting Dave. I presume Dellortos would be there or thereabouts too.

I guess it’s also impacted by engine condition to. Yours is freshly built with nice clean inlet/outlet ports and values, do no carbon build up to inhibit the flow. So maybe yours just breathes well.

Really interesting this stuff

[Alfastrut]

I've just checked mine. Both are around 2. That's the sud with 1.5 on webbers and 33 1.7 on dellortos

[Alfastrut]

I should have read the instructions for the Air flow meter!

It says 1.8-2.5 for Weber carbs is the "experienced" figure

What's funny is non of use actually read the instructions

[Sprint88qv]

Thanks Alfastrut, good info to have for future reference. Every little nugget of info helps.

I’ll check/adjust mine again when I awake it from it’s winter slumber.

Dave, as you say, yes always good to read the instructions

[Sprint88qv]

I finally found where I had referenced the air meter settings......I had made a note in my workshop manual of “should be under 3 kg/h”

However, I have no idea where I got that from....I obviously got it from someone along the way... :-0

[alfadave]

Got both my carbs down to 3 kg/h, and it got through the MoT ok today

[Alfastrut]

Well that answers my question.lol

[Kegsti66]

Got both my carbs down to 3 kg/h, and it got through the MoT ok today

Great result

[Sprint88qv]

Nice one Dave

[Sprint88qv]

Of interest Dave, did you feel any difference in performance between your higher airflow settings? Just of interest.

Ed

[Sprint88qv]

I hate predictive text....between your different airflow settings..

[alfadave]

I didn't run it with the higher air flow figures.

Didn't have MoT or tax......and lots of cameras near me!

[Sprint88qv]

Good decision

[StescoG66]

Pic for attention

Another thread resurrection folks. Mine passed MoT ok but was undoubtedly lean, measuring 0.97 according to the tester. Pulls great, cleanly apart from a strange 'pulsing' sensation on a steady cruise. I figure that pulling the plugs and checking after a run is as good a way as any to check if mixtures are OK, and I have a light brown on bank 2-4 and a grey on 1-3, both of which are OK although 1-3 is a little lean. However no matter what I do, I cannot get 1-3 to enrichen........on bank 2-4 I have mixture screws out 3.5 turns and on 1-3 they are out 4.75. Synchrometer reads 3 on all 4 ports. Car holds a great steady tickover too - actually sits beautifully at under 900rpm.
Should I pull the jets and clean again or is there somewhere else I should be looking.

[KevJTD]

When you are refering to 0.97 are you sure that it's CO your talking about or the Lambda reading, which has a threshold between 0.97 to 1.03 as a fast pass rate...
CO level for that car/year should be a max 3.5%, anywhere under 2% is decent.
Be sure what you are trying to achieve..

[StescoG66]

Just trying to get it to run spot on - it pulls great just at a steady cruise there is this 'pulsing' that is annoying - put even a light pressure on the throttle it disappears. May try blowing the jets out perhaps in case it has some crud following winter lay up.
Also playing on my mind is number of turns out on mixture - seems to be more than others however I suppose that should not matter.

Edit: just had another thought. Could it be restricted fuel flow on bank 1 & 3? Obviously on that carb the inlet goes to lower flange with return out the top - no choice. On bank 2 & 4 I have same. Therefore feed from pump into lower flange with feed to other side coming from top. Should this be the other way round thus ensuring a constant feed?

[alfadave]

Have a good read of sprint88qv's post on Nov 10th on page 1.
Your mixture screws seem out a long way. I usually start at 2.5 .

Also there are small holes in the carb top, next to the idle jets. Make sure these are clear, as they can easily block with dirt

Could your pulsing be ignition related?

Colour tune very useful for mixture setting. A set of 4 is best, but just one will get you by

[StescoG66]

Hi Dave - yes I used that guide when I first set up, it was invaluable. I also have a pal who has set up so many carbs check everything I have done too. Its more frustrating than anything else as the car runs and pulls really well.......

I am going to check the fuel pipe arrangement as I wonder if I have the inlet/outlet from the pump the wrong way round and maybe bank 1-3 is suffering from some starvation.........

[alfadave]

Seems your fuel pipe arrangement is correct.

Have you tried new NGK plugs?

[alfadave]

On my LH (2-4) carb , I have fuel in at bottom entry and fuel out at top, feeding RH carb.

On my RH (1-3) carb, I have single entry . Eurocarb 11067, or 12311, depending on bolt size.

On the pipe feeding the RH carb, I have Eurocarb 99901.415 8-6 mm reducing tee, which the 6mm fuel return connects to. Positioned approx above the pump

Never had a problem.

All fuel lines changed to ethanol proof of course, including dropping the tank to change the pipe on top of it!

[StescoG66]

Seems your fuel pipe arrangement is correct.

Have you tried new NGK plugs?

i have Denso W22 plugs on currently - they were new and are a three electrode design. I also have a set of Bosch WR78X available which I may try, however yes perhaps I should seek out the NGK BP6ES and try that.

[Alfastrut]

I'm having similar problem to you. How ever I try to set the carbs I'm getting a stumble when at low revs. it goes away at 2800 revs so it's on the idle circuit. It will idle lovely. The problem only shows up when driving. The engine is a 1.7 on 40 dellorto's. It's running 52 idles at the moment. I've ordered some 55 idle jets to see if it runs any better.

[Veesix75]

Rolling road is the place to go, worth the cost overall.

All my engines have purposely run just slightly lean, set up that way on the rollers for torque and power. A stumble on sub 3k revs could be too rich. Appreciate non of mine have been Road use so different circumstances.

Just as an extra, are the floats adjusted to spec and level both sides?

[StescoG66]

Thanks VeeSix and all.

Floats are fine on both sides. I have one side running ok -plugs are a nice silver grey - and the other lean. Accompanied with a bit of pinking -a sort of ting ting ting sound on over run. It’s getting better though.
I am not going to get too hung up on how many turns out the mixture screws are I think. Just concentrate on getting it running right, although I did clear the jets again which also helped a bit too

[alfadave]

What air filters are you running?
ITG/ Pipercross etc pull more air than original.

I had old ITG ones and bits of foam got in the holes next to the idle jets, blocking them and causing a problem.

I only use K&N now

[alfadave]

Eurocarb website shows how to check float level on Dellorto

But I previously had Weber sidedrafts and found simply bending the float tabs was a very crude adjustment.

I got the correct fuel level from a forum, and adjusted the tabs to achieve this.