Stumbling Edelbrock 1409, 4.3l, V6

[Rick Stephens]

So as noted in other posts, I just finished dropping a newly built 4.3L Vortec in my boat. I needed to lower my overall engine height by a smidgen to fit my doghouse, and the original QJet, on an adapter plate, also had missing choke parts and was pretty corroded from weather. So a 1409 Edelbrock and the 1485 calibration kit were in order. Nice carb, nice setup. Great that 1996 Merc OEM parts for the Weber assist in a clean install.

Took it out this week first time. 800 foot elevation on the Snake River. Starts, runs awesome except when just cracking the throttle no more than 10-15% the motor falls flat on its face. Drop the hammer 25% on up and it runs perfect. Pull the throttle back down to 10-15% above idle and it runs fine. So just that first little bit is lean - really lean, feels like the motor died, although it keeps running. Accelerator pump setting on highest and working. It does not self correct over time, either. Or at least I didn't have the patience to wait on the stumbling motor long enough for it to settle in.

Reading over the fairly simple Edelbrock calibration charts quickly leads to the realization that the 1485 kit is off the charts. There are no small adjustment parts available except for rod springs. My thinking here is the 4.3L is really kind of below the designed engine size for the 600 CFM carb and the 1485 calibration kit is all there is in that neighborhood.

Sorry for being so long winded here. But seems to me the only small adjustment I can make is to try a stronger metering rod spring so I get a little pop off the rod with moving the throttle up that little bit. It is either that or opening up ports inside the carb, which seems counter to the easy methodology of the Edelbrock/Weber line.

Any thoughts?

Thanks!

Rick

 

[NHGuy]

Rick,

Did you put in the kit or did you start with the as delivered setup? If not I'd say put in the kit complete, as it's for the engine you have.

Here is the instruction page link http://www.edelbrock.com/automotive/misc/tech-center/install/1000/1404_manual.pdf

Those carbs come out of the box for the 305 or 350 if I understand what their literature says.

From the instructions...

If your vehicle has a mid-throttle driveability problem that is encountered as the throttle is gradually opened, but then goes away upon further opening, it may be possible to eliminate the lean spot by using a stronger Step-Up Spring. The available Step-Up Springs are listed in the following chart along with their respective ?staging? point. It is best to select a new spring on the basis of vacuum readings, but in the absence of a gauge, try the strongest spring (highest vacuum rating) to see if the problem goes away. If the drive problem is cured by the strong spring, try the next weakest spring as well. If the strong one does not help, then the calibration problem is related to the A/F metering stage of either the Cruise or Power Modes. Use the Calibration Reference Chart to help select another combination.

Spring Color Blue Yellow Orange Pink Plain Staging Vacuum
3" 4" 5" 7" 8" ("Hg)
A complete set of these springs is available separately as Edelbrock part #1464.

 

[NHGuy]

I bet Bondo knows what to do, he has that engine.

 

[Maclin]

Watch the pump linkage and make sure it starts moving as soon as the throttle moves.

 

[Rick Stephens]

Rick,

Did you put in the kit or did you start with the as delivered setup? If not I'd say put in the kit complete, as it's for the engine you have.

Here is the instruction page link http://www.edelbrock.com/automotive/misc/tech-center/install/1000/1404_manual.pdf

Those carbs come out of the box for the 305 or 350 if I understand what their literature says.



Spring Color Blue Yellow Orange Pink Plain Staging Vacuum
3" 4" 5" 7" 8" ("Hg)
A complete set of these springs is available separately as Edelbrock part #1464.[/COLOR]

Indeed, I bought the regular 1409 and the 1485 kit and installed myself. The kit was exactly as described and easy peasy to install. I was thinking of trying the 5" spring that came in the 1409 instead of the 8 that's in the 1485 kit. See if I can jump a little needle on opening.

Thanks!

Rick

 

[Rick Stephens]

Watch the pump linkage and make sure it starts moving as soon as the throttle moves.

I will do that. I pulled the thermostat housing off since my temp gauge wasn't moving. Have to reassemble to live test anything, but should be able to see the pump action without firing it off. And easy enough to pull the carb off to look it over or change anything.

 

[Bondo]

Any thoughts?

Ayuh,.... Get yerself a copy of the 1488 calibration kit,....

You'll be able to change just the needles, or just the springs to tune it up,....

A jet change, Probably ain't needed,.....

The kit has oodles of needles, 'n all the available springs, in sets,.....

 

[Rick Stephens]

Ayuh,.... Get yerself a copy of the 1488 calibration kit,....

You'll be able to change just the needles, or just the springs to tune it up,....

A jet change, Probably ain't needed,.....

The kit has oodles of needles, 'n all the available springs, in sets,.....

Makes sense to me - thanks. I have to test under load, which means an hour drive to get to water - I live in the sticks. SO I'll probably get that kit before I next drive to test.

 

[Scott06]

Rick,
If you try a Google search on the subject you'll find some old posts on here and also marine engine forum detailing several others with the exact same issue with a 1409 and 4.3. Consensus was the 1485 kit was designed for pre vortecs and vortecs need a it a couple notches richer. This will probably shave some time reinventing the wheel with your tuning kit.

 

[Rick Stephens]

Rick,
If you try a Google search on the subject you'll find some old posts on here and also marine engine forum detailing several others with the exact same issue with a 1409 and 4.3. Consensus was the 1485 kit was designed for pre vortecs and vortecs need a it a couple notches richer. This will probably shave some time reinventing the wheel with your tuning kit.

Thanks Scott. I had also done those searches and seen those posts. You would think ten years would be enough for Edelbrock to update the kit.

 

[Bondo]

Makes sense to me - thanks. I have to test under load, which means an hour drive to get to water - I live in the sticks. SO I'll probably get that kit before I next drive to test.

Ayuh,.... The needle, 'n spring changes are quick, 'n easy,....

Just don't drop one of those tiny screws down the carb,.....

My Merc was runnin' W a y Rich when I 1st put it together,....
Trollin', the raw gas stench at the transom was nasty breathin' as I rigged lines,.....
It was years ago, 'n I don't remember where I ended up, but it was several steps leaner, but with the original jets down in the body of the carb,....

 

[Rick Stephens]

So I think I am going to try the 5.0L needle and spring with the 4.3L jets. The needle is profiled a lot thinner and should give me richer low throttle settings. I'm just hoping it is not too rich. But at least I'll learn something. Spark plug wrench and me are going to have some quality time together.

 

[Scott06]

I found this thought it was interesting fir those trying to read plugs http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

 

[Rick Stephens]

I found this thought it was interesting fir those trying to read plugs http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

That's a pretty good 'discussion'. Plugs still look brand new after the maiden voyage with this engine. Clean and tough to read, not hot or cold though, so close to where it needs to be..

 

[NHGuy]

Rick,I'd try to use the program in the manual. It gives you a nice set of choices. Plus gives you the why's and etc.
I do agree to cure your lean condition add fuel.
It runs OK above light throttle. So I'm thinking that when the vacuum falls and the springs raise the rods to their thin ends' the carb calibration is closer than it is just above idle.

Seems you are lean right above idle. I think you want to add fuel to the part of the rod that's in the jet when the rod is down during high vacuum. At that point it's fueling from the fat part of the rod...I think.
Too bad there's no rod that only reduces diameters to the fat ends compared to the one you have in there. What about trying that .065" X.052" rod with the.089" and progressively larger jets?? Or just start doing jet changes, with the rods you have.
Good luck and keep telling us how this goes.
I am adopting you as my learning coach.
I need to set mine up for my bigger engine when I launch in June or May.

 

[Rick Stephens]

Rick,I'd try to use the program in the manual. It gives you a nice set of choices. Plus gives you the why's and etc.
I do agree to cure your lean condition add fuel.
It runs OK above light throttle. So I'm thinking that when the vacuum falls and the springs raise the rods to their thin ends' the carb calibration is closer than it is just above idle.

Seems you are lean right above idle. I think you want to add fuel to the part of the rod that's in the jet when the rod is down during high vacuum. At that point it's fueling from the fat part of the rod...I think.
Too bad there's no rod that only reduces diameters to the fat ends compared to the one you have in there. What about trying that .065" X.052" rod with the.089" and progressively larger jets?? Or just start doing jet changes, with the rods you have.
Good luck and keep telling us how this goes.
I am adopting you as my learning coach.
I need to set mine up for my bigger engine when I launch in June or May.

So I called Edelbrock. Guy I got was a bit impatient but he did get the point across that shorter rod is what I need. He wanted me to order the.065 x .047. I think he got confused by the stock rod. I got his point and ordered up the .065 x .057 and the .065 x .052 - 1460 and 1461 respectively. I'll try the .057 first. Also can spring it one higher in vacuum which opens the rods earlier.

I read a post somewhere where the poster said the goal on the springs is to get the rod to pop up when you first open the throttle, just for a split second giving that little bit of extra fuel, and that indicates you are right on the money. Engine runs like ye old stripped reared ape when the throttle is open.. Just need this little tweak.

 

[Rick Stephens]

Ayuh,.... Get yerself a copy of the 1488 calibration kit,....

You'll be able to change just the needles, or just the springs to tune it up,....

A jet change, Probably ain't needed,.....

The kit has oodles of needles, 'n all the available springs, in sets,.....

Bondo,

Thought I would get back to you on the suggestion of the 1488 calibration kit. Unfortunately, that kit's parts are more center of the road for your average 327 or 350 cubic engine. The parts in the kit are not in range for the 1409 with the 1485 calibration kit. The 1485 kit, and the 4.3L engine, is far outside the calibration charts for a SBC engine and the range of the rods and jets for calibrating it to the 4.3L is not within the usefulness of the standard calibration kit like the 1488.

I thought I better mention that in case anyone reading this needs to duplicate the efforts.

Thanks for all the assistance! I can't wait to get back on the water and test things out.

 

[NHGuy]

Take a look at the 1486 kit. It has a lot of the sizes that ought to fit into your use. I think you could get most of the best possibilites that way in one box.

http://www.edelbrock.com/automotive/...ibration.shtm

 

[NHGuy]

BTW there is also the possibility that the stumble you are getting is too much fuel.
I found a troubleshooter chart at the end of the carb manual. If you check out the troubleshooter and symptom chart, it seems to point toward your stumble indicating rich not lean.
So, I apologize that I have been advising you to add fuel. If it IS rich adding fuel could worsen things. I guess you need to try out what you determine yourself.
I really do want to help, but this is theory which you get to carry out.
'm just trying to learn so that both of our tunes go as quick and easy as possible.
Jeez what to do, but follow the book.

 

[Rick Stephens]

Take a look at the 1486 kit. It has a lot of the sizes that ought to fit into your use. I think you could get most of the best possibilites that way in one box.

http://www.edelbrock.com/automotive/...ibration.shtm

Too late. Monday I will have spring kit and the two .065 long meter rods. I'm going to piecemeal it. I have a set of jet reamers in hand as well, so if I need to work up I can just start twisting.

THanks for the kit ideas. I am trying to avoid spending $60 if I can get away with $25.