When to run a stall converter?

From a dead stop going straight if i hammer it i dip into the high 16s low 17s it does produce a small burnout and then just accelerates decently. The stock stall and 256 gears are killing me. Starting from a corner i get good afr readings in the 11s and 12s and burn the tires through 2nd gear decently. If I am cruising and mash the gas the afr dips into the high 11s but mostly stays in the 12s. No bog or hesitation. I need a decent stall and I have a governor recalibration kit to install in the tranny that should help performance too. I accidentally did something the other day that was limiting how far my secondaries were opening...my secondary idle screw was too long and was hitting on my choke horn when the butterflies opened. This actually improved my low end power tremendously. More confirmation that I need a smaller carb or something with adjustable vacuum secondaries. Embarrassing to mention such a rookie mistake. Lol

 

Have a look at this info it may help. Mark wrote this while tuning my car:

Here goes...

Carb Tuning with Wideband and Vacuum

This is not an all about carbs guide. I’m not going to show off knowledge of fluid dynamics and venturi effect, or talk about pressure differential. I’m not going to talk about annular vs downleg boosters, or explain all the emulsion functions, internal passages, or what they do. I’m also not going to show you where the idle speed or mixture screws are. In fact, I’m not going to show you where anything is.

This guide assumes you know a bit about carbs, and are serious about really tuning it in. If you weren’t, you wouldn’t have a wideband and vacuum gauge hooked up. I will explain how to change each circuit for its intended operating range, and how to avoid common tuning errors of fixing symptoms, with the wrong circuits. Following these steps will give you the best balance of economy, and full power potential.

Base timing, and advance curve must be set prior to tuning. Refinements can be made later on, but it must be close to start. To set base/initial timing, start the engine, run until warm, then set a quick idle mixture. Set the idle RPM to the lowest idle that won’t stall. Advance or retard the timing until the highest vacuum at the chosen rpm is achieved. The idle speed screw will need to be turned with timing adjustments to keep the rpm the same, so this could take a while.

After this initial timing is set, check the amount of advance with a timing light. Write this down in a tuning log. You will then need to limit the total advance either with bushings, or in some cases, the slot must be partially welded, and filed to allow the correct amount of advance. If your initial timing was set at something high, like over 20* you might want to pull the initial back until you know how much mechanical advance you’re getting. Once the total amount of advance is proper, you can return the initial to the setting you wrote down. Choose a set of weights and springs that gives full advance at an RPM that is typically recommended for your engine. Most like around 2500.

Make sure you have the float level and fuel pressure set for what is recommended by the carb manufacturer, not your buddy, or that guy who solved his lean condition by running 12psi at idle.

This will get you close enough to dive into the carb circuits. If you didn’t already do this when installing the carb, pull it off the intake (I know, how annoying) and see where the transfer slot exposure is on the primary side. It should look like a square. You can put a jam nut on and lock it down which will prevent you from screwing with it later on, pun intended. This is important to isolate the idle mixture from the off idle/cruise mixture. With the carb back on, readjust idle speed if needed using the secondary screw, or if equipped, “idle ease” adjustment. Note that carbs with the idle ease, or 4 corner idle will need the secondary transfer slot set as the primary.

Now, to begin some baseline settings. Because of differences in combustion efficiency, compression, overlap etc, engines will “like” different AFR’s (air to fuel ratios). Acceptance of this is critical to optimizing your engine’s manners. This is why we will be using the trusty vacuum gauge once again before using any wideband data.

Idle Mixture:
This is a basic one, but it will greatly impact how you go about tuning your carb’s off idle/cruise circuit. More on that later. Warm the engine up to typical operating range.
Bottom out the mixture screws, then back them out 1-1 turns. Working in equal amounts for driver’s and passenger’s sides, turn them in turn at a time, maybe even less, until the engine wants to die, but still stumbles along without doing so. Note the AFR.

This is the absolute leanest it will run at, but poorly at that. Now do the opposite, but do it for the highest vacuum reading possible. IGNORE the wideband at this point! Be sure not to go above the highest vacuum reading. Only open them up enough to hold the highest steady vacuum reading. Do this like you did for base timing, and readjust idle speed so you are getting your vacuum readings at the same engine speed. Only use the secondary idle speed screw, or if equipped, idle ease for speed adjustments. Don’t change the primary setting. Okay, now you can look at your wideband, and note the number.

This is where it “likes” to be, but will quite possibly be a very rich figure. Mine for example idles buttery smooth at a 12.0, but will tend to foul plugs quicker. It also idles as lean as 16 but sounds like it has a huge cam. At this point, lean it out until the vacuum, or rpm drops just a little bit, but doesn’t produce the choppy effects seen at the absolute lean mixture. This is going to be your best compromise of smooth idle, and clean plugs. Note this AFR.

Main Jets:
“But what about IFR (idle feed restrictors) and IAB’s (idle air bleeds)” you shout!? We will get back to them later. The selection of the main jet is a tough one to get your head around, but here is the real basic concept. The main jet needs only to be large enough to support flat, level cruise at engine speeds of approximately 2000-4000rpm. 4000 is really pushing it too. Who cruises at 4 grand!?

Warmed up to normal temp, drive the car on a flat level road at 2500rpm. Hold the throttle steady, and observe the wideband. You should be able to get away with 14’s for AFR at this range, even with a fairly radical engine because the combustion process is better than at idle, the advance is likely”all in” and there is very little load. If the engine is too rich, jet it down attempting to get it as lean as possible. This is where it doesn’t matter what your buddy’s engine likes, or some Honda tuner. Go lean until it starts surging or develops a steady miss. Go back to the leanest setting that doesn’t surge or miss, and note the AFR. Keep in mind that a steady miss could also be an indicator of a vacuum leak, ignition problems, or poor distribution. The vacuum gauge would be really jumpy if you had a leak though.

Going to a best lean cruise will likely create some drivability symptoms. This is where most guys say, “it needs bigger mains”. WRONG! Those problems will be cured with other circuits. Now we’re going to go back and flatten the fuel curve from idle through the 2500 main jet selection.

Idle Circuit Refinement:
To get a nice smooth fuel injection quality fuel curve, you’re likely going to have to modify some passages in the carb. Make a chart of idle, 1000rpm, 1200, 1500, 1800, 2000, 2200, 2500. With the engine warm, run the car at those speeds in neutral, just sitting in the driveway. At each of those speeds, carefully hold the throttle steady, and watch the wideband. Throttle movement will cause the readings to jump, so take your time, and let it find a steady number. Don’t just jot down the first steady number you see. Wall wetting from accelerator pump, leanout from slowly throttling down, etc can take a good 20 seconds or more to “clear out”.

There are 2 things we’re really interested in. Remember that good balanced idle AFR we achieved earlier? Is the number at 1200 richer or leaner? Is the number at 1800 richer or leaner than that? If the 1200 number is richer, the IFR (idle feed restrictor) needs to be smaller. If leaner, the opposite. If the value at 1800 is richer than at 1200, the IAB (idle air bleed) needs to be bigger. If leaner, the opposite. This is the area where most in town cruising occurs. This is where you can either get max economy, and clean plugs, or a swilling fuel drunk neanderthal that needs the plugs removed and cleaned every week.

This is also an area that requires a lot of time. Since the air bleed can affect the entire curve, you should change it with the restrictor. It should be a good match from the factory, but if the feed restrictor needs to go down, the bleed will seem to have a much more pronounced effect on the curve. As a general rule, if the restrictor goes smaller, the bleed will likely need to go smaller with it to maintain a flat curve. Change one, then the other, a little at a time until your fuel curve is smooth. Also, keep in mind that most engines will want a slightly richer AFR at, and just off idle. If that is your case, the curve should smoothly lean out from idle by around 1500rpm to what the mains tolerated, then stay there into the main circuit.

Carbs with screw in bleeds have it easy. If yours doesn’t, you will either need to experiment with wire to reduce the diameter, or best bet is to drill and tap the stock ones for 8-32 brass set screws. You’ll use the set screws later on too, so it is worth pulling the carb apart for this, and the ones mentioned later. If you read this whole thing first, you’ll know which ones to do. Same is the case for the IFR’s. If you don’t have screw in ones, drill and tap, but the screws will likely need to be smaller.

Another thing to consider is that air bleed changes in the idle circuit will tend to have the opposite effect on the signal to the mains. This is because by reducing the air going through the idle air bleed, more of it then pulls through the main. There could be some changes needed in the main jet after refining the idle circuit, but should be minimal.

Time for a test drive! Drive the car at varied speed, and terrains. With the idle circuit and mains smooth and lean, it could result in poor throttle response, and falling on its face under moderate part throttle acceleration. Why would we tune it like this then!? We will now begin curing drivability symptoms with the proper circuits!

Get the car up to a steady speed, say 25mph, then smoothly push down to accelerate. Don’t romp on it, but don’t baby pedal it. Think of trying to go up a slight hill, or smoothly pass someone. If the car’s AFR plunges lean, watch the vacuum gauge. Look for the lowest vacuum reading that it runs nice at, then the point that it stumbles badly at. Note those vacuum readings.

Accelerator Pump:
Next, romp on the throttle from a dead stop. Do it both to throttle, and full throttle. It needs to be an immediate stab of the gas, not a roll into the throttle. Watch the AFR, and behavior of the car. If it goes lean, and recovers, but doesn’t stumble during that lean spike, you’re probably okay. More likely, is that it will pop through the intake, or stall, or come close then recover. Occasionally, it will go really rich and bog, then clear out.

If the first situation occurs, enlarge the primary squirter until the throttle stabs are responsive, with no stumble or stutters. If the second situation occurs, go smaller until it smooths out. Do the same on the secondary to cover the full throttle stabs. I have found that with the double pumpers, equal squirters front and rear works best, but you might experiment with a smaller one on the primary for economy, and a bigger one on the secondary for full throttle hits.

Power Valve:
Once you can romp on it from a dead stop, go for another test drive. Most of the drivability issues should be gone now. The next step is to optimize the power valve, and PVCR’s (power valve channel restrictions). If you roll into the throttle, you will see the vacuum gauge drop. You want to watch the AFR for a lean out above light throttle, or a rich bog. If it goes rich too soon, a lower power valve needs to be used. To get close, use the lowest steady cruise vacuum reading you got from the first test drive. Go1-2 numbers lower for the PV. For example, if you have a big cam, and only pull 8” of vacuum at cruise, a #6 power valve should be used.

In most mild street and strip combos, the car will starve out for gas before the power valve opens because of lots of vacuum, and the lean main jets. This is where most folks put in bigger mains to cover it, but the best bet is to put the right power valve in, and “jet” the power valve circuit via the PVCR’s. Like with the low vacuum combo, pick a PV that opens just below the lowest part throttle vacuum reading. In some cases it may require a really early opening valve. The most aggressive one Holley makes is a 10.5.

After changing the PV watch the AFR’s as it comes in. You’ll know when it opens by watching the vacuum gauge. When you are under a part throttle, but not full throttle load, and the vacuum is below your PV opening point, look at the AFR. If it is lean, the PVCR’s need to be bigger. If it goes rich, they need to be smaller. If lean, use a pin vise set, or if you have steady hands, a cordless drill, to enlarge the passages a few thousandths at a time until the AFR under load is around a 12.5-13. For max economy, favor the 13. For max power, it will probably pull harder around 12.5. Experimentation will be required to find what your combo likes best. If it goes too rich, you have to reduce the size of the hole. Some folks have gotten away with JB weld, and redrilling, but the best bet is to drill and tap the holes to accept 8-32 brass set screws. This will allow you to keep a few sets to go back and forth with.

Secondary Jets:
Now for the fun part, full throttle blasts! Take the car somewhere you can run it out for a couple gears, while watching the AFR. Obviously a track is best, but do what you can and be realistic about the fact you will be distracted by gauges and need nobody else driving near you. I suggest running it out moderate throttle in first gear, opening it to full as you hit second, staying in it through redline, and a little bit into third. If the car goes lean, or pops or does ANYTHING weird, don’t stay on the throttle. As with the power valve, tune it for max pull. It is probably going to be around 12.5 that it pulls the hardest, but some are stronger a little lean, some like a fatter mix.

The last bit is to watch for a difference in AFR as it approaches your shift point. If it starts to lean out, the high speed air bleeds need to be a little smaller. If it gets richer, they need to be bigger. Again, carbs with screw in bleeds have this easy. If not, drill and tap for the same 8-32’s you used on the IAB’s and PVCR’s. This can take a lot of time and effort, but having an awesome running car is worth it!

The wideband can be a great tuning tool, but it can also become a sort of car guy illness. You can get real finicky and watch the wideband more than the road. Remember a carb isn’t fuel injection, but can be tuned dang close! At some point you have to decide when the car runs well enough, and just enjoy it. Also note that the aggressive initial timing, and lean mixtures can cause some pinging at light throttle. An adjustable vacuum advance can be used to cure that. If the pinging cannot be cured with timing, you might need to slightly enrich that portion of the fuel curve and compromise some economy.

 

I saved it to my phone a long time ago. It helped determine my ifr size. One thing that I'm finding in my research is that moving the ifr to the bottom location like a regular Holley can drastically improve idle quality. It requires tapping threads though.

 

Reid,
You ever get your a/f ratio dialed in ?

 

No.

2 months ago I started building this addition on my house. Combine that with guttering 10 to 12 hours per day I dont have time to mess with the car. I drive it occasionally and everything is pretty good except for the rich idle which affects low cruise all the way up to like 40mph or so. I have decided that it definitely needs a stall converter. More Stall will allow me to idle a little leaner while in gear with the brakes held. Currently the car wants to die if I drop it into gear with like a 13.5 idle. Once in gear with the brakes held it barely stays running. If I richen the idle screws it runs just fine and smooths out but that is idling at 11.5. I am going to try some bigger idle feed restrictors and slightly bigger idle air blades. I actually have the parts to try. I just haven't had time. Also got to figure out why one bank occasionally reads 2 whole points leaner than the other. I'm gonna do a carb swap and see if that improves. If so I may possibly have an Internal vacuum leak or some blockage in the carb.

 

Looking great!

 

We put a wood burner in our 3 season room when this was added to house keeps the entire house warm in winter. Looking good!

 

I have a wood furnace in the basement but thought about adding a little pellet stove to this room. It's been a pretty big project. The rest of the house is getting new soffit, fascia, and roof as well.

 

Pellet stove great idea I was thinking of that myself for basement, You'll like that room when your done we sit in ours all the time. We don't air condition it either as there is a sliding glass door there just open all the windows watch the outside happen.

On your carb if things are starting to look too wacky on getting it dialed in go back to the base settings and maybe you missed something along the way. you just might be untuning it by trying to achieve a perfect setting and maybe the carb just can't get to where you want it.

An idle that is running fat is going to wash out those cylinders then you will have a bigger problem. Get it where you want it on the floor and tune the idle with the idle jets to get the highest vac and the lowest curb idle you can get (650 in gear) and highest vac reading forget the afr gauge.
Use 2nd gear from 2500-5000rpm to do the afr where you want it or where it should be for on the floor fun .

then play with the part throttle cruise with the front jets and that is about it. The pump shot is just playing with cams and shooters and there are 2 different kinds there too. you probably know all this crap so you'll just have to play with it some more but try going more back to base setting and try to keep it simple.

The power valve is usually a 6.5 and that depends on the cam if a lot more radical you want that number lower 4.5 or so You don't want it coming on unless you are on a 1/3 throttle+ The little stabs on the gas should be taken care of with jets up front and the shooters plus cam. Not really the power valve it is what it says it is.. power at least 1/3 throttle probably just estimated guess there.
You may not find that perfect spot between power valve and jetting along with the screw in air bleeds they are carbs pretty generic compared to fuel injection, but they say the Q-Jet can be tuned like fuel injection. lol so go figure.

 

I spent a couple hours on Monday playing with my car.
First I installed the edelbrock and sure enough my afr readings were very consistent from bank to bank. But I went for a test drive and quickly remembered howcrappy that carb is for my setup. Lol. the quickfuel out performs it every where.
I started cleaning my quickfuel and did the following:
I went back to a 4.5 power valve
One size bigger on the secondaries
One size smaller on the primary
4 sizes small on the high speed bleed
2 sizes bigger on the idle feed restrictor
5 sizes bigger on the idle air bleed
Installed Thompson blaster plate under pump nozzle
Added 1/4" carb spacer
Installed 60% linkage for the secondaries to delay the opening rate. (Stock is 40% opening rate)
Bolted it back on and immediately had consistent afr readings from bank to bank. Before one side might be 12 and other side might be 14 or so. Was able to get it to idle nicely around 12.1 in gear it's around 13.5 the afr is almost spot on every where. It's still too rich while coasting but I can live with that. I was able to do a 50+ foot long burnout with out a break stand. This was on hot black top. My smile was big. Lol. I tried to duplicate that burnout again but the carb leaned out after a few seconds. I drove back home and was going to go down a couple sizes with the accelerator pump squirter to extend the pump shot but unfortunately I stripped the threads for the squirter in the main body of the carb. I was upset but realized this happens alot. I watched a YouTube video and ordered a helicoil repair kit. Hopefully will have it back on the road next week.

 

Good work

 

I drilled and tapped the pump nozzle threads and installed the helicoil. Had to redo the helicoil a couple of times to get the depth just right but after a couple of ridiculous hours of screwing with it I got it all back together. There is a small gas leak at the base of the nozzle but doesn't seem to be effecting anything. I can't drive it yet because it has rained 5 inches here in the Last 12 hours. Gravel driveway is basically mud. I'm just glad I didn't have to buy a new main body for the carburetor.

The Thompson power blast plate is awesome to watch in action. It totally changes the characteristics of the pump shot.

The helicoil kit I got from eBay came with everything.

https://www.ebay.com/itm/302351818265

 

The rich idle is still too rich and has fouled the plugs. Performance is lacking. Afr is perfect everywhere except for idle and low speed cruise/coasting. honestly think I'm going to buy a dual plane intake for this thing. The sp3 is too picky. Or its the carb....not sure. Tim from TA doesn't really agree with the description on the TA website about this being a hybrid intake that performs equally well on a stock/mild motor. he thinks I will see big improvements with my low speed drivability and carb tunability with the dual plane. Anyone got one I can buy or try out?

 

Check with Fox Den. Maybe he'll swap you his d/p for your sp3. Pm him.

 

No. I've only messed with it a couple of times all summer. My July 7th update was where I made my most progress. It's just not where I want it though. I'm dealing with low speed drivability issues that I cant tune out. And a rich idle.

 

Hard to get a 4brl to act like it's a 2brl.

 

Is there a 750 CFM double pumper spread bore style carb? I think the smaller primaries would be alot better for throttle response.

 

There should be I have the 650 spread bore. I think you have tuned your carb out of the ballpark.
I don't even need a choke and it will start instantly and idle all day.

 

Remember where I was Right out of the box? the fast idle wouldn't engage at all and really wouldn't idle, secondaries throttle blades completely closed, it had power valve restrictors 10 sizes bigger than what was supposed to be in there it was rich into the 11s and 12s occasionally into the 10s on the afr gauge this was across the whole rpm range and it bogged almost as bad as the edelbrock. Its 10× better now. Starts good and accelerates good it just seems no matter what I do the low speed drivability just sucks, taking off from a stop sign might work great 9 out of 10 times but the 10th time it sputters and almost dies or does die. If I mash it from every stop it does great. Maybe I have a warped main body or something...it ain't right...i know that for sure.