Rich idle is killing me

[91r/t]

Not sure....going to rip into it tonight. I will measure them first thing in the AM at work and then I can go from there.

 

[91r/t]

i'd measure what the IFR is first; probably .036"-.038". I did notice in an older QF catalog a Q850 with .070" IAB's, but seen a 850-2 with .073" IAB. sometimes the dash numbers indicates a revision. .073" would be an easier change if you have them. I thought you might have been running a bigger cam than that. what type of ignition? my internet is out at home so reply's may not be too timely.

Try 0.035 to 0.40 for the idle restrictors or smaller if needed. Also do you have restrictors installed for the t-slots? It may or may not need them.

So I tore into it and then ran to work quick to measure the jets. They are .036 IFR jets. The gaskets are blue and were sooty all along where they sit against the idle slot from top to bottom which makes me think its way to fat at idle. Are these jets like normals jets? Go down/up a couple sizes at a time?
68 HEMI GTS I knew I was missing someone on the callout in this post!!!

 

[68 HEMI GTS]

How big are your holes in the plates? I like no transfer slot showing on the rear and very little on the primary. Ideally you should move the IFR to the low position. Probably low to mid .030’s. IAB is close. .070-.073 is where it’ll probably want to be. The PV size has no effect on the idle. Float level and fuel pressure are also important. Holley’s only need 5-6#

 

[91r/t]

How big are your holes in the plates? I like no transfer slot showing on the rear and very little on the primary. Ideally you should move the IFR to the low position. Probably low to mid .30’s. IAB is close. .070-.073 is where it’ll probably want to be. The PV size has no effect on the idle. Float level and fuel pressure are also important. Holley’s only need 5-6#

One hole in each blade 3/32". Transfers were almost nil in primary and small in secondary. I figured the opposite to limit fuel pulled in by the primary circuit. I shall re-eval that. The jets need to stay up top with this metering block as I cannot thread the bottom hole. No provisions or space that I can see. I was thinking of maybe going to a .034 IFR (2 sizes down) and then if need be going to a 72 IAB to fine tune if its real close? Or should I try and drop down to a .033 which is 3 sizes?

 

[91r/t]

I would try downsizing the IFR's a couple of sizes first. I have had better luck with changing idle A/F with the IFR's than the IAB's. IAB's seem to affect everything whereas IAB's concentrate on just idle.

How many sizes did you drop at once. This thing is pig rich man....Like light fuel smoke coming out pipes at idle and burn your eyes!

 

[68 HEMI GTS]

One hole in each blade 3/32". Transfers were almost nil in primary and small in secondary. I figured the opposite to limit fuel pulled in by the primary circuit. I shall re-eval that. The jets need to stay up top with this metering block as I cannot thread the bottom hole. No provisions or space that I can see. I was thinking of maybe going to a .034 IFR (2 sizes down) and then if need be going to a 72 IAB to fine tune if its real close? Or should I try and drop down to a .033 which is 3 sizes?

Try .033. I feel like there is something else going on if it’s that rich. How are you adjusting the screws?

 

[91r/t]

Try .033. I feel like there is something else going on if it’s that rich. How are you adjusting the screws?

Vacuum gauge. Max vacuum is about one half-ish turn out from closed, but it acts lathargic and starts harder like its a tad lean so I leave em around 3/4 out from closed on all 4 corners. It seems to be pig rich and I figured worse I can do is try and take some fuel outta it at idle and see how it runs. The tips are black inside and it leaves exhaust staining on the yellow paint on the tail by the tips. The plugs electrode and porcelain looks great a nice greyish brown about halfway around the curve which makes my timing pretty good too. The ring on the face of the plug looks sooty after idling or pussyfooting it around. Couple that with the smoke and I feel I have an idle issue fuel wise but have the other circuits dialed in close.

 

[68 HEMI GTS]

I never use a vac gauge to set idle. Reset your transfer slots. reduce the IFR.s. Open the idle screws up a bit and start it up. Slowly turn one in until the idle starts to fall off. Back out half turn. Work your way around the carb doing the same thing to all corners.

 

[91r/t]

I set the idle via transfer slots I am sorry misunderstood. I set the idle mixture screws via vacuum gauge. I can try this method too. I was kinda doing this via gauge and by ear. If it fell off I gave it a quarter turn out and ended up at 3/4 out all 4 corners. I will do this after I try the .033 IFR jets and see what I come up with.

 

[Bigal75]

If they're 0.034 then make a huge change that way you will know you're on the right track. Try 0.025 and see what happens.

 

[91r/t]

If they're 0.034 then make a huge change that way you will know you're on the right track. Try 0.025 and see what happens.

They are at .036 and I really don't wanna make a huge *** swap if I only need to drop 3 sizes ya know? Wasn't sure how sensative this circuit was. I am sure with the bigger cam and cubes, it will want more fuel than a stock 383 or 440, so wanted some opinions.

 

[hunt2elk]

How many sizes did you drop at once. This thing is pig rich man....Like light fuel smoke coming out pipes at idle and burn your eyes!

2 or 3. Enough to notice a difference. Stick your 33's in and see what happens. Curious if something else isn't going on like stated above also. I always read that the butterflies dont need to be drilled until you have a fairly radical motor?

 

[91r/t]

2 or 3. Enough to notice a difference. Stick your 33's in and see what happens. Curious if something else isn't going on like stated above also. I always read that the butterflies dont need to be drilled until you have a fairly radical motor?

This cam is fairly large for the street I’d say. It’s engles second highest grind from most radical.

 

[68 HEMI GTS]

Generally I end up with drilled plates on the smaller carbs with big cams. Doesn’t seem to be needed on the bigger butterfly carbs like dominators.

The IFR is usually tuned for idle along with part throttle. If you shrink it, you’ll just open the idle screws up, if its bigger you close them. Long as the carb is on the idle circuit and there’s adjustment in the screw you can reach your desired A/F target at idle. Most people target 3/4 to 1-1/2 out. It’s when you rev it up and pull some vacuum that the sizing really comes into play and it becomes a balancing act. I usually run larger IFR’s in my dominators. .040-.042 range. Keep in mind with a big cam, even if it’s idling at 14:1 its still gonna spit out a ton of exhaust fumes compared to something with a stock cam. The reason I don’t like a bunch of transfer slot showing on the secondaries is it’s another fuel supply under high vacuum cruise. That’s usually the trick to all this is getting the low speed cruise leaned out.

 

[HEMI-ITIS]

Check this site out! You can thank me at Carlisle https://www.tapatalk.com/groups/racingfuelsystems/

 

[91r/t]

.033 and .030 IFR jets should be here today! Also ordered some .072 IAB incase I want to fine tune with those instead of the 70's. Figured I'd get all the **** at the same time because of shipping charges. Nothing in stock at the local speed shops anymore so grabbed it all at once.

 

[HEMI-ITIS]

Have you considered drilling your own bleeds?You would need the proper drill set,but when you need one that you don't have..........I have 2 carbs so it doubles the fun.You can open a bleed but you can't make it smaller!

 

[lewtot184]

the thing needs more air. .036" isn't big but .073" IAB is were i'd start. I think you need to weaken the fuel circuit not necessarily restrict it. the the larger air bleed will reduce the fuel circuit sensitivity. i'd also get the centrifugal advance in as fast as possible and maybe forget the vacuum advance; if your using it.

 

[91r/t]

I never use a vac gauge to set idle. Reset your transfer slots. reduce the IFR.s. Open the idle screws up a bit and start it up. Slowly turn one in until the idle starts to fall off. Back out half turn. Work your way around the carb doing the same thing to all corners.

Have you considered drilling your own bleeds?You would need the proper drill set,but when you need one that you don't have..........I have 2 carbs so it doubles the fun.You can open a bleed but you can't make it smaller!

the thing needs more air. .036" isn't big but .073" IAB is were i'd start. I think you need to weaken the fuel circuit not necessarily restrict it. the the larger air bleed will reduce the fuel circuit sensitivity. i'd also get the centrifugal advance in as fast as possible and maybe forget the vacuum advance; if your using it.

So I installed the .033 IFR and put 72 IAB in it tonight. I have since realized that this motor will not idle below 850-950 RPM without running pig rich. I raised the idle using the secondary screw and ran it up to 950-1000 in which it cleared the idle up considerably. I fear with the big cam, and 8.5-9 in/mg. of vacuum, there is no way it'll clean up at the low idle. It seems to run alot better idling at 900 or 950 then at 800 all day long. The idle screws are a smidge under 1 turn out on all four corners. I think I have got it atleast do able for now with how it is at the moment. I am going to a car show Wednesday, so I will take it for a ride after all my idling and tuning and clean the plugs off good for a good blast. I will then judge where I am at after a little cruise.

 

[68 HEMI GTS]

So I installed the .033 IFR and put 72 IAB in it tonight. I have since realized that this motor will not idle below 850-950 RPM without running pig rich. I raised the idle using the secondary screw and ran it up to 950-1000 in which it cleared the idle up considerably. I fear with the big cam, and 8.5-9 in/mg. of vacuum, there is no way it'll clean up at the low idle. It seems to run alot better idling at 900 or 950 then at 800 all day long. The idle screws are a smidge under 1 turn out on all four corners. I think I have got it atleast do able for now with how it is at the moment. I am going to a car show Wednesday, so I will take it for a ride after all my idling and tuning and clean the plugs off good for a good blast. I will then judge where I am at after a little cruise.

Sounds like you’re on track, they usually take some playing with. If you maxed out on initial and the butterfly’s are still too far open you can always add a touch more bypass air.