IDF jetting

[RoyBatty]

I have been tweaking on my IDF setup for the last week to get my 1800 to run smooth and clean throughout the RPM range. The engine is stock so far as I know, save for the pertronix module in the ignition and the 4-2-1 exhaust system. And I have removed the California smog equipment from the engine.
My final setup at this time is as such.
F11 tubes with 140 mains and 200 air bleeds.
Installed the part number 00 pump spill jets
Opened up my stock idle jets from 52’s to 60’s and was able to get rid of the stumble during acceleration thru the 2000 to 3000 RPM range.
The idle mixture needles are all opened about ½ turn for best lean condition.

My Spider has taken on an whole new personality. Where before it was quiet up front and a decent amount of fun to run up and down thru the gears as you listened to the sweet exhaust note….
Now it is a borderline beast. The rumble from the carbs as you accelerate is inspiring and almost totally drowns out the exhaust. The time I have spent tuning and tweaking has paid off and I have no regrets on my purchase of this carb/manifold combination.

It might be nice for future IDF purchasers, to list what has worked for those of you that have tread this path before me.

[131]

I've been doing much the same, I've put an 1800 head on my 2 litre with 40/70 inlet cam, 70/31 exhaust cam, extractors and a 2" exhaust. The carbs are off a 124 BC 1600, so I started with F11 tubes, 210 air correctors, 135 mains (I think) and 55 idle jets. It was too lean on the idle circuit so I've gone up to 60s, but it's still a bit off so I'm considering 65s. It's still a bit cantankerous on the idle circuit and transitioning to the mains, but it's huge fun when it gets on to the mains, so that's where I've been driving it, I don't think my fuel economy is going to be very good.

[RoyBatty]

131,
Before you step up to larger idles, maybe try going up to 140's on the mains.
The mains will have some effect on the idle if I understand right.
I am not sure what effect your cam specs will have on the carb jetting. I am guessing that they will help make more top end power and make you possibly need more fuel at WOT.
Is the engine pulling strong all the way to the top of the rev range?
Seriously with the combination I settled on for jetting, my engine again has the tractability of the original 32/36 -single plane setup, but with more fun noise and much better power.
Winning!

[131]

Before you step up to larger idles, maybe try going up to 140's on the mains.

I had considered that, might give it a try. What I should do is fit the O2 kit I built and take the guess work out of it.

[RoyBatty]

What?!!
And take all the black magic out of the process??
Blasphemer! Burn him! He's a witch!

[131]

Management's just about got all the cooking sorted for lunch and guests will start turning up in 1/2 an hour, so no chance to play today. Unless I can hunt them all out the door by mid afternoon on the pretext I have more important things to do.

[131]

I went from 130 up to 140 on the mains last, it was a slight improvement but still lean on the idle circuit with the occasional spit back through the carb. I've gone to 65 on the idle jets this morning and it's a different car, tractable and responsive, a pleasure to drive. I'll go back to 130 or 135 on the mains and see how it goes, no use leaving the bigger ones in it if I don't need them.

[RoyBatty]

Nice!
Do a couple full power acceleration runs before and after you change the mains.
Not like I need to tell you that.
I'm just wondering what the "seat of the pants" and the spark plug check will show you.

[131]

I'm just wondering what the "seat of the pants" and the spark plug check will show you.

I had a ball yesterday afternoon, I picked up my son from work and headed south, up and down a reasonable hill with some great sweeping bends, to meet up with my wife to do the obligatory xmas chat with her Grandmother. She's 95, still lives at home by herself and is as sharp as a tack. On the return leg we were sitting in a line of traffic in the 100kmh zone behind a mobile chicane doing 70kph, a subaru behind him went passed and I followed him, as we pulled back in I looked in the mirror and a black Ford XR6 (4.0 litre 6 cyl. sedan) was pulling in behind me, he'd overtaken about 6 cars and overtook us on double lines as the oncoming traffic passed. About 2 kms up the road it went in to dual lane, so I hurried up a bit, didn't bother chasing him on the straight but went after him when we got in to the twisty stuff, he saw me coming and went harder but I kept gaining on him. I sat on his bumper until we got in to the straight stuff again then backed off. The next lot of twisty stuff he just moved over and let me go, I think he got quite a surprise from the little Fiat. I'm really impressed with my latest performance tweaks.

[RoyBatty]

Just made me feel the need to go and wander aimlessly in my Spider!
Update:
Yesterday 12/30/13, I took a couple of friends for a quick run to get their opinions of
whether or not I got it right. They are both italian car guys. One actually owns
a Ferrari Maranello and the other is a professional car mechanic that cut his
teeth on Lancias, Fiats, Alfa, and such. They both came away from the test drive
smiling and agreeing that the car is running as if it had the stock carb on it
except for the extra power and induction sound. One test the mech had me do was
to shift into 5th a bit early and lug the engine to see if it would misbehave.
No problems at all, I did a slow power application from about 1500 RPM in 5th
and the engine never stumbled, popped or faltered.

Thanks to everyone here that has posted helpful info in the many other threads having to do with the
dual IDF setup.