Popping and Lean on Decel- Dual Weber IDF's Options

[tornik550]

I have been trying to dial in my carbs (dual weber 44 idf's). I recently made a jet change (and no other changes). Now I am going lean and popping on decel. I did not have this issue before the jet change which makes my doubt an exhaust leak. My air fuel gauge reads 14.5 at idle, 11 on accel and 17 on decel. The changes that I made were decreased the air corrector jet to 200 (from 210) and increased the main jet from 145 to 150.

Since it is so freaking hot out I want to be prepared before going outside. The engine is running fine. Head temps were around 290-300 after hard acceleration. Ideas?

[mrbubblehead]

I have been trying to dial in my carbs (dual weber 44 idf's). I recently made a jet change (and no other changes). Now I am going lean and popping on decel. I did not have this issue before the jet change which makes my doubt an exhaust leak. My air fuel gauge reads 14.5 at idle, 11 on accel and 17 on decel. The changes that I made were decreased the air corrector jet to 200 (from 210) and increased the main jet from 145 to 150.

Since it is so freaking hot out I want to be prepared before going outside. The engine is running fine. Head temps were around 290-300 after hard acceleration. Ideas?

i suggest reinstalling to your fist configuration. and make one jet change at a time. you will get real good at removeing and installing your air filter....

i have one question. why are you increasing your mains if your a/f ratio is already at 11 at wide open throttle? you are too rich already. your target a/f should be 12.7-13.2 at wide open throttle. i would try a 130 or 135 main. then report back with your numbers.....

[tornik550]

I have been trying to dial in my carbs (dual weber 44 idf's). I recently made a jet change (and no other changes). Now I am going lean and popping on decel. I did not have this issue before the jet change which makes my doubt an exhaust leak. My air fuel gauge reads 14.5 at idle, 11 on accel and 17 on decel. The changes that I made were decreased the air corrector jet to 200 (from 210) and increased the main jet from 145 to 150.

Since it is so freaking hot out I want to be prepared before going outside. The engine is running fine. Head temps were around 290-300 after hard acceleration. Ideas?

i suggest reinstalling to your fist configuration. and make one jet change at a time. you will get real good at removeing and installing your air filter....

i have one question. why are you increasing your mains if your a/f ratio is already at 11 at wide open throttle? you are too rich already. your target a/f should be 12.7-13.2 at wide open throttle. i would try a 130 or 135 main. then report back with your numbers.....

I will give that a shot. I changed the jets cause I was about 14 on had accel- especially above 3000 rpm. I changed the air and main jets mainly due to impatience.

[KaptKaos]

With MrBubbleHead's (Doug's) help, my 40idfs are singing.

Not sure I can add much, but wondering what you idle at?

[tornik550]

With MrBubbleHead's (Doug's) help, my 40idfs are singing.

Not sure I can add much, but wondering what you idle at?

I'm idling at 1000 with the engine hot.

[mrbubblehead]

drop down to 800 rpm hot. then reset your MIXTURE screws to best lean idle.

what is your timeing total adv?

[KaptKaos]

With MrBubbleHead's (Doug's) help, my 40idfs are singing.

Not sure I can add much, but wondering what you idle at?

I'm idling at 1000 with the engine hot.

Seems a little high, but I would defer to Doug. Mine is about 800. Seems that if your idle is too high when you tune to best lean idle, it throws stuff off. I am not sure why yet. I believe that it has to do with bringing the secondaries online, but please take this with a grain of salt.

[tornik550]

drop down to 800 rpm hot. then reset your MIXTURE screws to best lean idle.

what is your timeing total adv?

I'm using a Mallory Unilite with 27 degrees total advance. The reason that I set the idle at 1000 was because if I had it any lower, it really wouldn't run cold unless I reved the engine. No big deal though.

[KaptKaos]

I believe that I had a similar issue. I was tuning for best lean idle, but I wasn't running on the idle jets exclusively. I had the idle adjustment turned in too far, which caused the butterfly valves to open just enough to engage another circuit.

My idle was about ~1100, and I would get lean pops all the time.

Again, I am no expert, but just sharing what happened to me.

[mrbubblehead]

drop down to 800 rpm hot. then reset your MIXTURE screws to best lean idle.

what is your timeing total adv?

I'm using a Mallory Unilite with 27 degrees total advance. The reason that I set the idle at 1000 was because if I had it any lower, it really wouldn't run cold unless I reved the engine. No big deal though.

i agree with the kapt....dont worry about the rough running when its cold. we drive em when the engine is hot. thats when you should do all your tuning. good and hot. go out and drive it then make your adjustments.

once you get a good tune, a couple of pumps of the accelerator pedal, and it should fire right up.

the kapt said it. when you raise the idle that high, you are using part of the progressive circuit to idle and thats no bueno.

my car pops a little on decel. no biggie. i could open the mixture screws a touch and it would go away.

[mrbubblehead]

27 degrees is fine for now. you may find that your engine might even need less timing. but 27/28 is a good start.

[rhodyguy]

it sounds like you're real close. leave everything as it sits and back one idle adj screw off the stop. this reduces the binding factor. chances are your idle will drop. if not, back the 'working' screw out a bit and see if the idle goes down. doing this does not affect the linkage adj you now have and worked so hard to achieve.

k

[mrbubblehead]

its been my experience that if you try and cut corners or do things half assed your results are gonna suck. if you have to readjust your linkage so be it. you will have to rebalance the carbs and then reset the mixture screws. its just how its done....

[rhodyguy]

do you mean what i suggested is half assed corner cutting? not trying to start flame up, just curious.

k

[mrbubblehead]

do you mean what i suggested is half assed corner cutting? not trying to start flame up, just curious.

k

yes, wouldnt you?