When you say IFR are you wanting the idle fuel feed restrictors or intermediate, transition, fuel feed restrictors?

Cab, I'm looking to richen the idle. I think richening the transition portion is probably needed, although I'm not sure how to evaluate that. I have a WB, but I doubt I can pull any intelligent data from that. If I can improve the idle quality, so it seems cleaner, chrisper, and the rpms don't drop excessibly when I put it into gear, that'll be great. If nothing changes, it's good enough to race it now. I'll experiment with the bleeds and see if it improves things.

I don't know if you should or shouldnt open the hot air bypass. But, if you need to reduce the throttle position, then the hot air compensator can be opened and used as a bypass. It will be like an 'idle-eze' setup in a different location.

As far as experimenting, measure some wire, measure the idle air bleeds with a pin gage or drill bit shank. Then stick the wire in each idle air bleed and see what happens. Write everything down.
The easy way to retain the wires is run them up over the choke tower (assuming its still there), then under the aircleaner gasket. I actually prefer to use one wire for both bleeds. It takes a little more time to bend and fit.

Opening the hot idle comp is a great idea for WOT, but would hurt me with trying to richen the idle. I'll have to save that idea for later. I'll update this after I do some adjusting.

is this a factory mopar holley? if so the idle jet is probably a tube in the main well and can be seen by removing the jets. and, if i'm correct they are very lean and reducing the idle air bleed helps.

Yes it is. thanks I'll have a look.

So I've tried tried putting wire in the idle bleeds. The original bleed size is .066" I used .014, .018, .030 wires. I gained about 50 rpm in gear, but did not really see much of a change. Vacuum is around 12 in. idleing. Mixture screws were 1.5-2 turns. Throttle plates all are drilled .120 and transfer slot closed up nicely, open about .030" I may try putting the timing at 20, 25 to see if it helps. Locked at 37 now.

It is. We can see it in the photos in the linked threads. There's a photo with the jets removed.

50 rpm less drop in rpm is progress.
.066 IAB = .00342 in sq
.030 wire = .00071 in sq
Equivalent of .059 IAB
You could try larger.
.035 wire would be equivalent of .056

However it is looking like what will be needed is larger IFRs.
I think the engine will like a little less timing at idle, but very well may need even larger IFRs then.
I've not removed the tubes from blocks, but several guys on RFS have. Besides Tuner, Deeproots, Hank, Mike all have with varying luck in not damaging them in the process. So its definately possible. I can try to put you in touch with one of them if you want. Mark who posted earlier in this thread, and Dom (Thumperdart) may have experience removing them also.

if you're allowed to change metering blocks, that might be the easiest solution, assuming all of the circuit connections line up.

the relationship between the idle jet (tube in the well) and the idle air bleed are screwed up on those mopar holleys. I always do the idle jet half the diameter of the air bleed, the old way was to just reduce the air bleed size. this was done by tamping a piece of #4 lead shot into the air bleed hole and drilling the lead. in this case the air bleed would end up at .044". I've done this before but really believe you need to go after this in both directions. reducing the air bleed gives a stronger signal to the idle circuit but those small jets will only flow so much fuel. the last one I did for a six pak I drilled out the idle jet to .028" (was .0023") and reduced the air bleed to .056" with the lead shot. those brass tubes won't allow a proper diameter jet but area wise small changes can make big differences in area. the hard part is going thru the bottom of the metering block to get to the idle jet and deciding how to plug the hole up. I used 6-32 set screws thinking I may want to get back in there to clean a jet up. I was afraid of removing the idle jet from the metering block and damaging them and not being able replace them. quick fuel makes a universal metering block that might be easier if nhra tech allows it.

Great info. I like the idea of going thru the bottom of the metering block. I will give it a shot. I could probably just change the metering block, but modifying the original will be much more fun

I would check and see if they will allow a replacement cast block be used, a Holley 11180 block will allow you to put adjustable lower idle feeds in.

i was looking on line sometime back and found some aluminum plugs for carb holes, believe it was Mikes Carbs, if you don't want to do the set screws. set screws will need to be sealed. I've found that playing with the air bleeds can help some but in the end it's fuel volume you need and the only way to increase it is bigger idle jets. I really go after idle jets anymore for lower rpm.

Unless the rules have changed, you aren’t allowed to drill the secondary blades.

I also don’t recommend “asking” if you could use different metering blocks.

i haven't messed with one of those carbs in 50yrs but I do remember not getting it to work properly. I lot of that was lack of knowledge when I was 22yrs old. this is off topic but I remember having real fuel control issues with those fixed needle and seats. I think they are something like .075" seats and they didn't like pressure. if you keep in mind that those engines came with 3-5psi fuel pumps and most of those pumps wouldn't do 5psi you can see were a problem could arise with a 6-8psi pump which is what I used back in the day. I don't know if there's a way to get creative here but I doubt that .075" seat can provide enough volume without overpowering it with pressure. the carb i played with had a small brass balance tube between the primary and secondary bowls. that brass tube may be necessary for the fixed needle and seats but might become an issue if you do get creative with different needle and seats.

Actually I don't understand how this would help at WOT. It's just a small air passage. Yes?
At idle, consuming 4 to 6 cfm, or maybe 8-10 with a high idle rpm, the compensator will flow a small but noticible percentage of that.
At mid to high rpm, WOT, its going to be a tiny fraction of a percent.
(It's not like a bleed into the circuit which alters the pressure difference and the density.)

Here's some of Mike's tips on removing those tubes without damage.

https://www.tapatalk.com/groups/rac...signs-and-assuming-not-t1793.html#p17512

That might be easier than drilling from the bottom unless you have a cross vise on a milling machine or drill press and can index the well accurately???

another thing that can help the situation is to open up the idle feed restriction in the secondary metering plate. the old bulletins say to open this up to .070"; that's a bunch considering it's probably .036". I would try this to help compensate for the primary side but I don't think i'd jump to .070" if I was doing the primary side mods. going to .40"-.045" would make a noticeable difference in area.

It's a pretty good size passage, I might try it sometime.

So I accessed the idle jet from the bottom of the metering block. It is indeed .022" I opened it up to .033" I've JB welded the set screws and will give it overnight to cure before it start it up again.

Thanks again guys for all the tips.

If you clicked on the first link Mattax posted there are some good pics of the baseplate.
I don’t know if all of this list number carb were the same as that one, but that carb had no actual secondary “idle” circuit.

There were only some slots/feed holes positioned well above the throttle blades....... so they contributed no additional fuel at idle....... so making the feed restrictions for that circuit bigger shouldn’t have any impact on the idle a/f ratio.

In one of the other links where another person was playing with one of these carbs, they also referred to the lack of that circuit, which is also used to keep the fuel in the secondary bowl refreshed.

don't be afraid to play with reducing the idle air bleed i.d.

I based my comments on a 1971 race bulletin carb mods. maybe the bulletin and me are off base,....lol.

I guess I would have used a fuel resistant pipe thread sealant.

.033 is a good starting point. Maybe a littlke larger than I would jchanged to in the first test but that's OK. That should give you room to drop the idle timing. Even if it means 10"Hg manifold vac, the restriction is less it may all work out.

As far as IAB and IFR. They do pair together. If you find the fueling is too rich off idle, or it needs a little trimming at idle, open the IAB up.
Don't forget you can also get some adjustment on the idle fuel ratio by changing the transfer slot exposure slightly.
So take the time to try different combos before drilling again.