FakeSnake

float level set to bottom of the sight plug where gas comes out with a fender nudge. tried closing them all the way and it killed the motor.

pill number 1 for the MSD 6010


i double checked the float levels, reset the throttle blades to expose .020 of the transfer slot and have no vaccuum leaks. after some tinkering the motor idles fine and will pull hard above 3000 rpms but once i hammer it from a dead stop it will sputter like its getting too much fuel then clear up and take off. i have tried every combination of squirter and cams possible to no avail. could a single plane intake, factory stall and factory camshaft be causing my issues? i am pulling 21 in/hg at idle and have seen 29 in on decel when i back off the throttle which causes pretty bad popping. i did try unhooking the secondaries and it revs clean and sounds pretty good. hook them back up and snap the throttle open and it seems like its not getting enough fuel. sounds like it cuts out but doesnt pop through the exhaust like its loading up.
exhaust is getting put on tomorrow with a O2 bung so ill be able to see exactly what its doing soon.

Edit Addition* will be blocking the power valve off and upping the pmj a few numbers to see if the power valve is dumping too much fuel once i hit 6.5 in/hg and less

Pop N Wood

iTrader: (1)

I have a stock cam and single plane intake but manual trans. I don't think a lot of idle vac is hurting you.

Try driving it with the secondaries disconnected. If it works well like that then you have narrowed your problem down to the secondary side of the carb.

I don't think pulling the power valve is the way you want to go. Especially if it runs good on just the primaries.

What is your set up right now? Jets, nozzles and air bleeds front and back? I assume the 20 thou transfer slots are front and back also? Make sure the accel pump arms are adjusted so even the slightest movement, primary or secondary, causes a strong squirt. There should be no slack in either pump arm.

FakeSnake

On the back transfer slot I couldn't uncover it at all or it would idle ridiculously high and I couldnt get the idle low enough with both plates set to show .020 the truck is at the exhaust shop and my book with all my notes is in it. Ill get back soon with the numbers. I did unhook the secondaries while at the track and it didnt stumble at all when the throttle was snapped open.

FakeSnake

So I put the wideband in and its idling at 10.2 to 10.5 goes lean to 15.8 to 16.2 when I hammer it and then levels out to about 11.8ish once the mains come in. Im thinkng I need to go smaller with the IFR and IAB's and see where that gets me. I have messed with the 4 corner idle screws and cant seem to get it any leaner.

89gmcs15

iTrader: (7)

I would do as they suggested an unhook your secondaries and see if the issue is still there. That will narrow down what side of te carb you should be working on. I'd recommend gettin your idle in gear an park leave out. If it won't lean out with the idle mixture screws you have something else wrong. You should be able to lean kill the engine with even one of those screws all the way in. You stomping the gas and it sputtering wont change with you bleeds and ifr changes, that all in the accel, pv, and jets

FakeSnake

Ill mess with it after work and report back

newschool72

iTrader: (12)

In an earlier post you said you thought the engine was getting too much fuel and played with the squirters and pump cams to fix it. Did you try going to a bigger pump cam to increase the pump shot when the secondaries opened?
It just sounds like the same problem everyone has with not enough fuel to keep up with the volume of air that is thrown in there when the back barrels open. As far as the air screws go, I have no advice.

FakeSnake

I wasnt getting any lean popping so I thought it may have been loading up, now it seems like it wasnt getting enough. Ill play with the cams and squirters in a few

wesmigletz

iTrader: (6)

I agree with pop n wood. You could try starting with a wire strand from a 12 gauge or 10 gauge wire. With this done, you should be able to adjust your mixture screws +/- 1 1/4 turns out.

It will clean your plugs up and help your mileage too.

jays78

Subscribed.

I am having the same issues, Iron block ls1, stock 2000 cam, Road demon 625 cfm, dual plane intake, msd 6ls.

Just got it together and trying to tune the carb, runs great at cruise speeds, slight bog when stomped but as soon as engine gets some rpms hold on!

Carb has 70s in primary 78 secondary, 8.5 pv. 19 inches vacuum at last check.

Idles so rich my neighbors are complaining! lol. Idle screws all the way in engine just idles higher. completely close front and rear idles screws engine still runs.

I first had pill number 3 in the msd, I switched to the number 5 to get more initial timing number 5 ran better than 3 but made the idle speed worse.

What should I try?
I thought of making my own timing curve maybe? less initial with quicker total like pill 5.
Try the IFR mod.

Ideas?

krochus

iTrader: (1)

How much of the transfer slot is uncovered on the primaries?

What power valve and how much vacuum at idle in gear.

Lastly where is your msd box mounted and how much timing at idle?

jays78

Transfer slots are a problem, to get them exposed cause idle to be above 1000 rpms, but it does make the air mixture screws work.

power valve is 8.5

msd is mounted on intake on the tabs, but I did have to make a bracket to slightly move it forward to clear accel pump on carb.

Timing is pill #5 at the moment which gives 15 initial 30 at 1000 rpms map sensor is connected.

Vacuum in gear is 18

krochus

iTrader: (1)

How much of the slots are you trying to expose?

I'd start with seeing how far you can CLOSE the secondaries. There is one screw hole in the performer rpm intake that if not plugged will be a vacuum leak directly into an intake runner

Was this a new carb?

jays78

Its a used carb I did go through it installed a rebuild kit.

Secondaries are closed, any adjustment on the secondaries has the same effect as primaries

I put sealer around the threads of the screw in the intake that goes into the runner.

I just check for vacuum leaks, none to be found.

I am going to go back through the carb, If I put a wire in the idle feed in the metering block to restrict fuel to the idle circuits give me the ability to open the throttle plates 20 thousandths over the transfer slots without high idle?

speedtigger

iTrader: (16)

Do you have PCV?

jays78

Good question

Yes I do and it gets complicated

I have a gen IV 5.3 block bored to ls1 specs, I used all the internals and heads from a 2000 ls1 gen III

So I have a ls2 valley cover for non dod so I used a orifice type pcv and tapped a hole in the intake because I used the one on the carb base for my power brakes.

I haven't tried adjusting carb without it, but I did reach over and pinched the hose while it was running it did give a slight reduction in rpm but no more than I have ever noticed from any other engine.

Pop N Wood

iTrader: (1)

With the blades completely closed and none of the transfer slot showing means the full engine vacuum is sucking fuel through the idle port.

Pull the carb and adjust both primary and secondary throttle blades so exactly 20 thou of the transfer slot is exposed. Then hook up a lap top to the MSD unit and back off on your idle timing to get the idle speed where you want it. Throw the pills in the trash.

I had the same issue, idle speed screw on the primary was all the way out and still idled at 1200 RPM. Backed off on idle timing, got the correct amount of transfer slot showing and everything was beautiful.

BTW, you only need to adjust the timing down at the idle speed (the 500 RPM set point). You can pop the 1000 RPM and beyond values back up once you get the carb so the idle speed is below 1000.

From this point on you can start messing with IFR, jets and bleeds.

Of course none of this will work if you have a vac leak or carb problem. You need to make sure things like all the carb passages are clear, air bleeds aren't blocked, float level is good, floats aren't leaking, gaskets are good and all sealing surfaces good and flat. A leaking power valve will make it rich at idle.

Don't forget to check the throttle shaft bushings for vac leaks. Sometimes they wear out on used carbs.

speedtigger

iTrader: (16)

Did you pinch off or plug the brake booster line too just to eliminate that as a vacuum leak?

jays78

Yeah, I even disconnected the vacuum line to the climate control.

jays78

Thanks, that is what I was thinking but just wasn't sure, I was hoping that someone had came across this problem.
I sprayed carb cleaner around the base, shafts, anywhere it could leak, with engine running with no effect.

I have never played with timing with a computer. Guess its time to teach this old dog some new tricks!