Twin carbs

[StescoG66]

I have a K & N panel bought from a very kind person on here. Goes in standard air box.

[junior]

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?

I would wholly agree, as I found mine performed across the range so much better after a rolling road session with Dave at Mech tune. Then despite having it set up slightly rich I have found the fuel economy much better.

[Sprint88qv]

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.

Would be really interested to know how you get on with those 55 idle jets. I’ve always read that the 52s run a little lean and to be honest I think everyone I’ve checked (both original dellorto and new replacements) has been undersized. So i ream them to exactly 52. Seems to run well but would love to hear if your 55s make a great difference. Cheers.

[NPG33]

Mine is running perfectly since a session with Dave at Mek Motorsport. Think he changed main jets, pilots and diffusers.

[StescoG66]

I am just doing a visual on the spark plugs to get an idea. One bank (Cylinders 2 and 4) the plugs are a perfect light brown colour. Bank 1 and 3 are a silvery grey colour so obviously lean. Air correctors are all closed, I turned the mixtures out another half turn before driving back 80 miles and just cannot get this bank to run any richer than is....... I took jets out and cleaned them last week , however I ran out of fuel the other night so could it have perhaps ingested more crud into the jets?? I really am stumped here......

[justsuds]

The problem may lie with the inlet manifold, some are very thin between the inlet tract and the counter bore for the mounting nut, so that the gasket may leak air into the inlet at small thottle opening when there is max. vacuum in the inlet. I have cured this in the past by removing the stud that is screwed into the head, and making an aluminium bush that is pressed into the manifold, with a smaller hole in it and using a socket head bolt to fix the manifold to the head - a drive shaft bolt is ideal !
I'll post more pictures later.
Cheers, John.

[alfadave]

Maybe spray WD 40 round the gasket to see if its pulling air?

[alfadave]

Do you have the four small rubber pipes coming from the oil filler neck to the carbs?

If any of those pipes are split, you could be pulling air.

[StescoG66]

Do you have the four small rubber pipes coming from the oil filler neck to the carbs?

If any of those pipes are split, you could be pulling air.

They were in a bad way so changed to silicone ones, along with the pipe for the vacuum advance to the distributor

[StescoG66]

The problem may lie with the inlet manifold, some are very thin between the inlet tract and the counter bore for the mounting nut, so that the gasket may leak air into the inlet at small thottle opening when there is max. vacuum in the inlet. I have cured this in the past by removing the stud that is screwed into the head, and making an aluminium bush that is pressed into the manifold, with a smaller hole in it and using a socket head bolt to fix the manifold to the head - a drive shaft bolt is ideal !
I'll post more pictures later.
Cheers, John.

Interesting. Will look at that

Maybe spray WD 40 round the gasket to see if its pulling air?

All seems good there too

I also checked floats - sitting at 8mm both which I think is correct.

Will clean jets again after running out of fuel in case have ingested more crud.

[StescoG66]

How does this jetting compare to others?

I am thinking of lifting idle to 55 as am 5 turns out on mixture and still have this pulsing at around 3000rpm

Have not driven the car again since I cleaned them all out with paraffin and my compressor, so maybe its solved.

Also had a slightly sticking needle valve which has been changed too (175)

Idle Jets - 50

Emulsion F67 + Main 140

Starter jet? 90F7

[Alfastrut]

I tried 55s and it totally bogged down. Didn't have time to play so put the 52s back in.

[Alfastrut]

Found this thought it would go well with this subject

[StescoG66]

I have had a look in that site - the samba - it’s good, and not about old Talbots

[Sprint88qv]

I tried 55s and it totally bogged down. Didn't have time to play so put the 52s back in.

Ah, guess that answers my question from the 2nd Aug then

[alfadave]

Are all four accelerator pump jets squirting fuel when you operate the throttle manually?

[Alfastrut]

Well I've managed to get My 33 95% running right. I'm not sure if the last 5% is in my head. I got it to where it is by taking it for drives and checking the plugs. They have all now got a nice even color on the tips. It seems I was running a little rich.

[Sprint88qv]

Great news!!