Hi All
I'm rebuilding a pair of 44IDFs off my 2L Spider. So far I've managed to strip them down pretty easily, and I've sent the parts off to be ultrasonically cleaned. In the meantime I've had a look at the jetting and I apparently have it all wrong! My setup compared to what I see in various recommended setups is:
Main jets: I have 125 instead 155 or 170
Emulsion tubes: F14 instead of F11
Air correction jets: 160 instead of 200
Idle jet: 60 (correct)
Pump jet: 40 instead of 50 or 55
Venturii : 34 instead of 36
Aux venturii: 4.5 (correct)
The engine is modified (gas flowed, fast road cams) but the carbs weren't supplied and fitted by the engine guy so they could well be wrong. I do remember the car drank fuel when it actually worked (it last moved 15years ago!) but I just figured it was because of my "performance" engine. Now I'm older and wiser (and poorer) so I'm looking for some sort of fuel economy compared to out and out performance.
So- what do I put back in? The stuff I have and then get it going and tune it or should I already replace some (or all) of the setup from the outset? Ideally I want to just buy new jets etc once, rather than buy the "baseline" and then replace stuff again as soon as I get a chance to tune the engine properly.
44IDF Rebuild - use what I have or what I "should" have?
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felahughes
- Posts: 16
- Joined: Sat Jan 24, 2009 9:17 am
- Your car is a: Fiat 124 CS2 1979
- Location: Barcelona, Spain
44IDF Rebuild - use what I have or what I "should" have?
Fiat 124 Spider (for 30 years- now being resuscitated)
Lancia Delta Integrale Verde York No 405 of 500 (a bit sick too unfortunately)
Lancia Delta Integrale Verde York No 405 of 500 (a bit sick too unfortunately)
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sptcoupe
- Posts: 987
- Joined: Tue Mar 17, 2009 9:25 pm
- Your car is a: 1972 124 Sport Coupe
Re: 44IDF Rebuild - use what I have or what I "should" have?
With the performance mods you have (not sure about a header or CR, or big valves) I would go with the following:
Emulsions - F11
Chokes - 36s
Aux venturis - 4.5s
Mains - 150s (160s will be ok)
airs - 190 or 195s
pump jets - 55s
bleed backs - 35s.
To get the range for your main jets on an F11 emulsion, multiply your choke size (36s) by 4.1 and 4.3, which is 147 - 155.
To get the range of your idle jets on an F11 tube, multiply the chokes by 1.6 and 1.7, or 57 to 160.
On an F11 tube, add 45 to the main jet size to get the starting point for the airs.
44s on our TCs are easier to tune if you use an F9 tube, which runs richer in the mid-range, and leaner on top than the F11. For instance, on the coupe's 2.0L full house motor (very deep breather), I am running F9s with 36 chokes, with 52 idles and 145 mains, with 185 airs. This allows me to keep a correct AFR ratio in the mid range ( 2000 - 4500 rpms - where you drive the most) and create a strong vacuum signal when I go to WOT. The result is a really smooth running motor with no flat spots, instantaneous throttle response because of the relatively small size difference between the main and the air correctors (stronger vacuum signal), and getting enough gas to the cylinders to allow the engine to rev and make real power to 7200-7500 rpms.
Each engine will be different depending on how well it breathes, but these will good starting points.
Emulsions - F11
Chokes - 36s
Aux venturis - 4.5s
Mains - 150s (160s will be ok)
airs - 190 or 195s
pump jets - 55s
bleed backs - 35s.
To get the range for your main jets on an F11 emulsion, multiply your choke size (36s) by 4.1 and 4.3, which is 147 - 155.
To get the range of your idle jets on an F11 tube, multiply the chokes by 1.6 and 1.7, or 57 to 160.
On an F11 tube, add 45 to the main jet size to get the starting point for the airs.
44s on our TCs are easier to tune if you use an F9 tube, which runs richer in the mid-range, and leaner on top than the F11. For instance, on the coupe's 2.0L full house motor (very deep breather), I am running F9s with 36 chokes, with 52 idles and 145 mains, with 185 airs. This allows me to keep a correct AFR ratio in the mid range ( 2000 - 4500 rpms - where you drive the most) and create a strong vacuum signal when I go to WOT. The result is a really smooth running motor with no flat spots, instantaneous throttle response because of the relatively small size difference between the main and the air correctors (stronger vacuum signal), and getting enough gas to the cylinders to allow the engine to rev and make real power to 7200-7500 rpms.
Each engine will be different depending on how well it breathes, but these will good starting points.