When to run a stall converter?

I don't run it that rich on the daily. I never messed with air bleeds or anything other than jets until after I got the afr installed. it has had a low speed stumble since day one out of the box. It idled so rich out of the box it made eyes water. It's supposed to be a super Street. Meaning that it's a streetable drag racing carburetor. Not for my build AT ALL. lol I am way too busy with life right now to do a stall converter, transmission, and rear end. I'm going to install a dual-plane on there and hopefully have an enjoyable car to drive and finish building the car after I've accumulated the rest of the parts.

 

You took a low compression 2 bbl engine & cammed it, nice big 4bbl & SP3 without all the other good stuff.

 

Then you bought a race carb that really belongs to Mart who has a big cam and more compression. Race style carbs do not belong on a engine that is not. They call it a street carb when it is really more race carb.
It is made to mash it on the starting line after a nice burnout, then it will squirt plenty of gas to launch off the line.

The no heat in the intake is the real problem with the stumble.

 

I did shave and port the heads along with valve job and steel shim gaskets. Wasn't just a cam. But either way I get the point. TA still claims sp3 runs equally well on a mild motor. "Hybrid" intake that doesn't lose any low end. I mentioned this to them when I called with some questions. Tim told me the sp3 was tested on a 400hp rollerized 350. It was never tested on a stock motor or mild motor. So...where do they come up with this info for their description? Maybe my carb just sucks

 

Same way they put this pkge together. I'll never understand why they recommend a 600 cfm carb to replace a 750 qjet....
http://www.taperformance.com/proddetail.asp?prod=TA_1235P

 

Do you know what your vac reading is at idle in gear and in park. and can you start to stall the engine when you screw in the 4 corner idle screws?

You said you were getting down to 10 on the afr gauge and that is way rich at Any time. 11.6 should be about the most Should be running at 12.5 when just on the gas midway I would guess

The car should not be running rich at idle to get the pump shot to stop a bog or bad transition to main system.
I still think you have that carb so far out of wack that you cannot get it to do anything.

Anytime the engine is bogging or stumbling you either are shooting too much gas at the moment and is too much before the main system starts or there is not enough.

I think you should go back to very close to carbs original setting and play with the shooters to get the stumble out. You could be going the wrong way on the pump shot. Ever try to put smaller shooters in and use the number 2 on the pump cam and use the cam that will give you a longer pump shot? This is the part you have to play with to get that stumble out. Playing with those air bleeds and all of that will get you in trouble and I think you use those to fine tune the carb in after you work out the other bugs.

Your car has more cam but with a more stock drivetrain and you could be giving it too much gas initially and possibly it just needs a pump shot that is not so strong at first but gets stronger as the pedal goes down.

Do you have the idle low enough to be able to stall the engine with the 4 corner idle system? If you can't with any of the 4 screws then it isn't right.

If you have a vac gauge and a rpm gauge to read the idle In Gear with wheels blocked and the e brake on you should be able to start to stall the engine with any of those 4 screws and all 4 be set so any turn in at 1/4 or less should bring the motor down 50-100 rpm on the scale or the vac gauge starts to drop. 1/8 on all 4 should bring the motor down at least 50-100 rpm This is where you need to be set at for the car to idle dead on the money.

I will sit there and play with all 4 of those screws to get the carb to slow down engine with a turn of any screw then I know I have it right. From that point then you could give those about 1/16-1/8 turn up to richen slightly but no more than that.
you have to get the main idle screw down low enough to be able to use the 4 corner idle screws properly, You can open the back 2 barrels of the carb to help you bring down the main idle so you are in that 650-700 range in drive. Try to get down to 600 rpm if you can and get that vac gauge to read as high as it can with those 4 screws along with keeping that 650 idle.
Then at that point you should be able to turn each screw in 1/16-1/8 and that engine should slow down.
It should really do it with 1 screw turned in 1/4 max.

I have a bigger cam and I know I can start this car up with 2 full pump of the gas pedal once the shooters have gas to shoot. and will sit there and idle put it in gear and back out of the garage without stalling The intake works great and for firing up and not stalling

you know you could have a intake leak in between the ports that you cannot see Mine blew out between ports and I did not know this until I had put the Sp3 on and this may have happened Way back in 2005 when I had a nitrous explosion thru the carb due to too much pressure from the bottle heater. Stick a camera with a light on it down in the ports and look to see if any of the gasket is sticking out of the port. This if you used the composite gaskets and not the original valley pan

Also you should be at 650 rpm in drive maybe 700 and I bet that is where mine is at right now.

You have one of the systems messed up in that carb and you should go back to base, start over and forget the afr gauge unless you are that pig rich. Get the idle afr right with those idle screws if you want to do that Then set the main jets with you r cruise in high gear on highway at steady pedal probably need what 12.5 or so then on the floor it should not go below I would say what maybe 11.5, 11 maybe but no lower.

you have idle, pump shot, and power and one of those 3 systems is not working right, It is a damn simple Holley look alike for gods sake and this should be a piece of cake!

 

I'll read more later. But I will say the first couple of weeks with the carb the only thing I messed with was cams, shooters, and eventually added a 50cc pump. Covering lean tip in with pump shot is not advised. Its a low speed jetting issue. Or just too big of carb. This carb sucked right out of the box for low speed drivability. I can reset it all back to factory here in a couple of weeks and shoot a video. I'm on vacation now. I can kill the car with the idle screws. Any time my tune gets away from that I go back with my adjustments.

 

I like your idea about using a camera in the port. But the edelbrock ran good at low speed and tip in. Transition etc. Leaning more toward carb. But I'll try to see if a friend has a camera

 

You think cruise afr should be around 12.5? Also, i have experimented with opening the rear throttle blades. This helps with cold starts but makes lean tip in stumble even worse. Rear blades are open to much it takes signal away from the primaries.

 

I am not exactly sure on afr cruise so I texed my brother who has a Stang with a Procharger to see what he gets with his and he is at 13-13.5 at 2000-2500 and if he pushes on the gas some it goes down to 12.5 I did not ask about on the floor as I think he is still working on that with the computer. Most engines like the same kind of afr at cruise and so on so this should be no different than yours.

I also see you have played with the secondary blades to help and yes it is touchy where it needs to be in helping to close the front. You may not have a big enough cam to make this feasible to use.

So you get this lean tip in as you are just cruising down the rd or is this more when you give it a good push like half throttle or so without the secondaries being pushed on?

When you step on the gas and it goes lean that is a pump shooter problem not a jetting issue. Jetting issue would be at your cruise rpm on the highway in high gear.

Try this trick to see if the carb is not leaking internally, plug both tubes to the bowls on the carb and it should stall after maybe 30 seconds or so.

You may benefit from a 1/2 inch 4 hole spacer to help breakup the gas before entering the intake.
I do not think your carb is too big something is a miss and just have to figure it out.
There was a place that had sold these deflectors that connect to the shooters that will help breakup the gas before it goes down the barrel.

Also do you use the shooters that have a tube connected to them or the ones without the tubes. The Tube ones do help to direct the fuel in but maybe those are not correct even though they may be the originals so I do not know which you have there.

May try putting a vac gauge in the car and ride around to see where it is running at.

 

Theres no stepping on the gas issue. I'm talking about very slight throttle movements leaving from a stop light or stop sign. The kind throttle movements that barely activate the accelerator pump. The kind of throttle movements that are supposed to be covered by idle and transition slot.

 

I have Thompson blaster plate installed under the shooter. Its sweet and took care of the idle to wot bog. It disperses the pump real nice. 28 squirter is what works best with my 256 rear.

 

I found videos on my phone. here are the links. You can see what's happening here. First video was after sitting at light for 30 seconds. It's a worst than normal example of what I'm dealing with. Scary either way, this was in des moines traffic and car about died. You can watch the afr...I try to ease into the throttle but almost dies i mash the gas and it dips into the 10s briefly and gets it going again. 28 swuirter... Second video is 65mph highway cruise. Once I'm in the mains the carb is beautiful. Cruise to WOT is seamless and those annular boosters really shine there. The idle circuit on this thing effing sucks though. This is a low speed circuit problem.

 

Check my last post. I just posted 2 videos so you can see what my car is doing. Also, am I wasting time trying a stock 4 barrel intake or should I go right for a stage 1?

 

I didn't know the engine sounded like music couldn't tell a thing. lol
Is the accelerator pump spring loose when at idle you should be able to have .010-.015 thous clearance between pump arm and spring When the throttle is on the floor
Does it squirt gas in the carb the moment you touch the throttle when looking down carb it should squirt something the moment the throttle is touched. It could need a new pump diaphragm and do you have a chart for the pump cams I am sure you do. It has to do that. Also I would put a new gasket under the carb and absolutely do not tighten the carb too tight I use two fingers at the head of the wrench. could still be a leak somewhere that stops that shot to over transition.

I would not put a stock intake on there it does you no good TA dp intake will work I guess could sell you mine I probably won't need it plus Mart keeps bugging me about it. It is port matched to ported heads.

I would put the same carb back on to see if the intake was the real trouble or not just sticking a Q-jet and a dp intake may cure the problem but did it really and what was the problem, the intake the carb or was it both or was it a bad intake seal.

I can't tell from the video if the carb is the problem too much music drowning out the engine. You would have to have the windows up to record in the car and hear the engine.

 

Did you watch videos?

I would still like to try a 650 double pumper...I think the smaller primary would give me the the off idle response I'm looking for. I will check with car guys in my community and see what I can find. The 750 sure does out perform my 650 eddy on the top though.

 

Watch the video again and watch afr and tach.

 

This could be ignition related believe it or not since the moment you touch the gas the electrical system has to juice it up so check the grounds in that system look at it at night for glowing ****