Webber ICT jetting

roofchop Seriously Crusin Dubber

177 posts · joined Jan 2011 · 2 Apr 2016, 8:19 am

#1025072

Hey there, as above, need help...

Engine is 1641, single port, stock heads, stock cam, Pertronix flame thrower, SVDA dissy, extractors and twin ICTs

I changed the jetting out of the box to (based on googling here etc)
160 air, F6 emulsion, 40 idle and 140 main

Ran the engine for a while and is sooty visible black smoke on acceleration and when I removed the heads, very sooty in there.

Additionally now I'm fitting an Engel 110 cam.

So, what do you recommend, just go down on the mains, how low??

Cheers
Dave

landfall Officially Full-On Dubber

290 posts · joined Jun 2014 · 2 Apr 2016, 9:19 am

#1025073

Dave,

I am currently running very successfully on:-

Main 150
Air 170
Idle 55
Em. F6

Similar specs to you.

roofchop Seriously Crusin Dubber

177 posts · joined Jan 2011 · 3 Apr 2016, 6:20 am

#1025095

Thanks for that, why do you think I'm so rich (not $$$)

Strange as I'm down a size compared to your set up...

Dave

landfall Officially Full-On Dubber

290 posts · joined Jun 2014 · 3 Apr 2016, 7:48 am

#1025098

Dave,

I can't answer that question, but I can say that I am about to remove the ICT's and fit IDF's next week.

I can only assume that my engine may have more go fast bits in it. I have MOFOCO 041 heads port and polished, slightly wilder cam and 1:1.25 ratio rockers, C/W crank with light flywheel.

Not that I am unhappy with the ICT's and have a feeling that they will be going back on? Oh well, as my wife says - "It's only money."

roofchop Seriously Crusin Dubber

177 posts · joined Jan 2011 · 3 Apr 2016, 10:19 am

#1025104

I see, your motor will easily burn up more juice than mine, pimped twin port, hotter cam rockers etc.

I might just try smaller mains and see...
Cheers
Dave

coletrickle Wolfsburg Wizard

661 posts · joined Apr 2009 · 3 Apr 2016, 6:30 pm

#1025111

You will do ok on recommendations but your motor needs what it needs not what you think it needs.You really need an air fuel meter to get them right.Good luck but keep on it and you'll get it.

psimitar Son of Jim - Creator of Good

2,506 posts · joined Jan 2009 · 4 Apr 2016, 6:59 pm

#1025141

The ratio between the main and air jets doesn't mean that 10 points higher on the air means you can go 10 points higher on the mains. IIRC it's more like 10 points on the air to 5 points on the mains.

I ran a 1641 with single quiet pack muffler for many years. Took me a while to figure the jetting and 009 spring rates to make it smooth from the previous owners out the box set-up.

Anyhoo, I ended up with

Idle 55
Main 135
Air 160
Em F6

With a 130 mains it would drive OK for short trips but would overheat and cut out on long motorway drives. Like more than 1.5hrs at 70mph. Went up to 135 and no more problems doing the long runs and the plugs were a nice grey colour compared to previously being glazed and speckled (too lean a mixture) 🙂

madness is in the eye of the beholder 👍

roofchop Seriously Crusin Dubber

177 posts · joined Jan 2011 · 5 Apr 2016, 7:10 am

#1025151

Thanks all, I will order 135 mains.

What do you think of my 40 idles, should I go bigger? (55s?)
Cheers
Dave

Dangermouse Learner Dubber

4 posts · joined Jan 2007 · 19 Apr 2016, 9:45 am

#1025556

I’m going through a similar situation with ICTs at the moment. 1600sp with Weber ICTs, car runs great with lots of power but has always seemed rich with sooty plugs and black exhaust pipes. I started out with 60 idles, 135 Mains which is how they came jetted by CB Performance for this application, at which performance was great but mileage was not what it should be. I also switched to F6 emulsion tubes and 170 airs. Really happy with the performance of this little engine but not convinced I have it tuned quite properly just yet.

• 1600 singleport
• Mostly stock but with Engle 100 cam and full flowed.
• Bosch 019 (centrifugal advance) distributor
• Stock mechanical fuel pump with Holley fuel pressure regulator (set to 3.5psi)
• Weber 34 ICTs were OEM new (Spanish)
• CB Performance SP manifolds
• Floats carefully set at 6.5mm
• I have a balance tube between the manifolds
• Driven primarily at sea-level.
• Vintage Speed exhaust
• Twin oil bath air filters

I thought the 60 idle might be a bit big resulting in poor fuel economy so have experimented with 55 and 52 idles which have actually carbon fouled plugs within a week to the extent that it would misfire terribly and barely run. Had to keep fitting new plugs (which in twin-carbed ’65 engine bay is no fun whatsoever).

My current hypothesis is that with these carbs the smaller idle jet sizes wouldn’t allow the engine to idle at all unless the idle speed screw is turned in more than it should be (1.5 to 2 turns max.), possibly exposing the progression holes and allowing fuel to be dumped in uncontrolled at idle. It’s counterintuitive, but a larger idle jet will let the idle circuit operate as it should without requiring the idle speed screw be turned in quite so far to get a steady idle. I suspect the 60 idle jet is still a little big as my mixture screws are at only one half to one full turn out from seated. I have some 57.5 idle jets coming next which I hope will be just about right.

Once I get the idling sorted out I’m going to put an AFR gauge on it and see what it’s doing under other conditions…

To the OP, your 40 idle jet sounds really small, check how many turns in on the idle speed screw are required to allow it to idle at all.

landfall Officially Full-On Dubber

290 posts · joined Jun 2014 · 19 Apr 2016, 10:56 am

#1025559

I purchased mine from CBPerformance and they DO NOT come jetted suitable for the engine. They simply come as they are jetted at Weber Spain.

Having changed mine now to IDF's I now have a pair of four month old Spanish Webers complete for a DP VW. Linkage pack is still in bubble pack along with air filter elements. Everything is there to fit straight on.

I used them to run my engine in 3,000kms.

psimitar Son of Jim - Creator of Good

2,506 posts · joined Jan 2009 · 19 Apr 2016, 6:49 pm

#1025575

It's been a real long time since I played with my 1641 with 34 ICTs but IIRC the idle mixture screw should have a starting point of 1-1.5 turns out from fully in and the idle speed screw start point is 1 turn from first point of contact of screw to throttle lever.

As my engine is virtually identical to Dangermouse's then I'd say go back to the 55 idles but before playing with the settings you should square off both ends of the manifold flanges and the bottom of the carb plus use some 0.5-0.8 gasket card instead of those crappy metal gaskets or cheap chinese card gaskets.

To square off the manifold and carb flanges just requires a sheet of plain glass on a nice thick benchtop, like the kitchen, and a file plus 120-400 grit sheets of wet n dry.
You use the file first to carefully file across the widest part of the flange and keeping the file as flat to the flange as possble. This normally shows up that the outer part of the flange where the bolts go sits proud of the centre section of the flange. So you file till you are getting file marks across the entire flange and then move to the wet n dry on the sheet of glass. Go from coarse to fine and change up each time the previous grades sanding marks can no longer be seen.

The reason for doing all this is after weeks of trying to get my ICTs working well I found that all of the manifold flanges weren't flat and this along with those shitty metal gaskets was allowing a small amount of air to leak in at the joins.

Once they were all flat I had the car running smoothly by the end of the arvo.

Never assume that a brand new part is well made unless it comes directly from BMW or Mercedes 🙂

Oh, and can't believe the web page I used over 15 years ago to tune my carbs os still up n running. Here it is Weber 34 ICT set up guide

madness is in the eye of the beholder 👍