Carb tuning

[Pmt133]

Good afternoon all. So after the fiasco with the water leak and the "pop" through the intake, which was documented here and finally fixed, ended up just being lean. I finally got around to swapping in the 4 barrel intake and carb. Spent the last couple weeks just running it and now I am at the point to need to tune it. The intake is the Edelbrock marine vortec V6 intake and the carb a good mercruiser/weber AFB pulled from a V6 mercruiser pre-dating my engine. I went through and tanked and cleaned the carb and threw a new rebuild kit at it prior to doing anything.

There is a thread on here where the carb jetting was roughly settled on and so, since I had those parts laying around from other projects, I started there. And I went out and was hard lean. Surging, not running great etc. So for my vacation 2 weeks ago I just threw jets at it and roughly ended up where a stock edelbrock 1409 would come for the weekend. And it ran fine but you could smell it was a little rich and upon pulling the plugs, yeah... rich, but not overly.

So now I have to get it dialed in. I've messed with carbs in cars before so I get what needs to be done. Now after being in this and in a Holley, for something this mild this thing is so much easier to tune in my opinion. Just seems more intuitive but there is a lot less you can mess with too. That being said, am I wrong in following the edelbrock guide for jetting and meter rod changes and then just checking the plugs for fine tuning? The edelbrock is more or less a carbon copy it seems... My plan right now is as follows:

• Throw a rod at it to go a little richer just to see if it gets worse... it probably will.
• Pull one jet size out of it and see if it gets better. Check plugs
• If better do that again until it stops feeling any better and look at the plugs. Fatten up a jet size then mess with rods at part throttle.
• play with rods until it stops feeling better then back off a step again. Check plugs
• Run the **** out of it and make sure plugs look fine.
• Enjoy

Am I in the ballpark here?

 

[Scott06]

there have been a few threads - I think in this one two guys ended up wit the same tune on a vortec 4.3 ... https://forums.iboats.com/threads/stumbling-edelbrock-1409-4-3l-v6.670697/page-2

another one

Edelbrock 1409/2114 on stock 4.3L Vortec engine

I?ve seen a lot of posts here from people asking if anyone has changed from a 2-barrel carburetor to a 4-barrel carburetor on a stock 4.3L Vortec engine. My boat is a 1997 Sea Ray 185BR with the Mercruiser 4.3LX Gen+ engine. According to the Mercruiser Service Manual #18, 4.3LX refers to the...

forums.iboats.com

what ever you do yes read the plugs but you have to do it such that you run at 'X" rpm for a few minutes, then stop it and pull the plug , otherwise you are just reading the idle mix....

on my 1409 I had some slack in the accelerator pump linkage that was causing a lean spot off idle and on holeshot. bending the rod to make sure the pump spring had taken up any slack cured it

 

[Pmt133]

there have been a few threads - I think in this one two guys ended up wit the same tune on a vortec 4.3 ... https://forums.iboats.com/threads/stumbling-edelbrock-1409-4-3l-v6.670697/page-2

another one

Edelbrock 1409/2114 on stock 4.3L Vortec engine

I?ve seen a lot of posts here from people asking if anyone has changed from a 2-barrel carburetor to a 4-barrel carburetor on a stock 4.3L Vortec engine. My boat is a 1997 Sea Ray 185BR with the Mercruiser 4.3LX Gen+ engine. According to the Mercruiser Service Manual #18, 4.3LX refers to the...

forums.iboats.com

what ever you do yes read the plugs but you have to do it such that you run at 'X" rpm for a few minutes, then stop it and pull the plug , otherwise you are just reading the idle mix....

on my 1409 I had some slack in the accelerator pump linkage that was causing a lean spot off idle and on holeshot. bending the rod to make sure the pump spring had taken up any slack cured it

Pumps good. I don't have a lean spot just feels like you'd expect a rich engine to behave. Little slow compared to how snappy it was when it was scary lean lol.

I started at ricks jetting (first link) and had all the odd surging and what not so I jetted up. Odd that second link is a bit leaner. I was reading by staying at speed for half hour then going key off at speed.... a little scary but did it. I wonder if because its a rebuild the cam is different enough I have to change jetting.

This was about 3 hours at 3200 before rejetting.


Same speed and time after jets:


I have an ottoscope I also use to look at the base of the porcelain as well. The second set has a nice Grey band where there was nothing on the first one.

 

[nola mike]

there have been a few threads - I think in this one two guys ended up wit the same tune on a vortec 4.3 ... https://forums.iboats.com/threads/stumbling-edelbrock-1409-4-3l-v6.670697/page-2

another one

Edelbrock 1409/2114 on stock 4.3L Vortec engine

I?ve seen a lot of posts here from people asking if anyone has changed from a 2-barrel carburetor to a 4-barrel carburetor on a stock 4.3L Vortec engine. My boat is a 1997 Sea Ray 185BR with the Mercruiser 4.3LX Gen+ engine. According to the Mercruiser Service Manual #18, 4.3LX refers to the...

forums.iboats.com

FWIW, that first tune is what I first went with and it was CRAZY lean. Also, IIRC the factory weber has 3 step metering rods vs the 2 with the 1409.

on my 1409 I had some slack in the accelerator pump linkage that was causing a lean spot off idle and on holeshot. bending the rod to make sure the pump spring had taken up any slack cured it

Interesting. Mine has been doing that for a while, only bothers me when trying to pull a skier. Have been planning on taking it apart, but maybe I'll look into this first.

Michigan motorz uses a stock 1409 as their carb for their vortec 4.3s. Personally, I think trying to plug chop a boat is voodoo unless you're way off. I know scott06 did it on his 5.0, but I think I'm the only one I've seen that installed an a/f meter to tune the carb on a 4.3. I got it almost right before other things took over. I was still a bit rich on the secondaries but otherwise was running around 14:1. Unfortunately, it doesn't appear that I ever documented what I ended up at. I'll definitely take note if/when I open the carb again.

 

[Scott06]

FWIW, that first tune is what I first went with and it was CRAZY lean. Also, IIRC the factory weber has 3 step metering rods vs the 2 with the 1409.



Interesting. Mine has been doing that for a while, only bothers me when trying to pull a skier. Have been planning on taking it apart, but maybe I'll look into this first.

Michigan motorz uses a stock 1409 as their carb for their vortec 4.3s. Personally, I think trying to plug chop a boat is voodoo unless you're way off. I know scott06 did it on his 5.0, but I think I'm the only one I've seen that installed an a/f meter to tune the carb on a 4.3. I got it almost right before other things took over. I was still a bit rich on the secondaries but otherwise was running around 14:1. Unfortunately, it doesn't appear that I ever documented what I ended up at. I'll definitely take note if/when I open the carb again.

yes some of the factory webber carbs used 3 step metering rods not sure which engines etc but there were a few. Can only think it shows that the binary rich/lean didnt work that well.

I found the pump rod linkage slop when I put the AFR meter on. I never would have found it unless I had the meter. It lead to a long lean spot post holeshot when towing for water sports. I was trying to jet around it so it would go way lean for a long period, then swing way rich. I think in the end I ended up basically where I started with it except for a bigger pump nozzle. Just straightening the rod to lengthen it was all it took.

 

[nola mike]

yes some of the factory webber carbs used 3 step metering rods not sure which engines etc but there were a few. Can only think it shows that the binary rich/lean didnt work that well.

I found the pump rod linkage slop when I put the AFR meter on. I never would have found it unless I had the meter. It lead to a long lean spot post holeshot when towing for water sports. I was trying to jet around it so it would go way lean for a long period, then swing way rich. I think in the end I ended up basically where I started with it except for a bigger pump nozzle. Just straightening the rod to lengthen it was all it took.

I've tried changing the holes on the linkage with zero effect, so that's interesting. Of course I don't remember if this has always been present or just since the big dunk.

 

[Pmt133]

Yes the three step rods were there but short lived. seems like .092/.089 and a 686457 metering rod vs the normal 6857. The reman engines seem to be back to the two step rods and that is what was in my carb. I've done the AFR route on the corvette and usually the plug reads agree with the meter so I at least know my eye is right.

I'd love to do an AFR meter but just seems cumbersome tossing those plates in and I don't think I have the room to go any higher on the elbow.

 

[Pmt133]

Haven't much messed around since my last post. Ended up getting a plate for a wide band just to confirm my suspicions with the tuning. Did run it on the trailer just to test it and she is fat. Seeing around 11.5 -12 at idle and dips to 10 at 1500 or so. I've had this wide band and confirmed it against my others on other vehicles so I trust it.

A pain to get the boot to fit with with the taller plate but I have it for now.

My experience has been they run a little richer in water so when the weather cooperates I'll get it hammered down. The last few weeks its been blowing 15-20 NNE which beats the hell out of you trying to do intricate things like tuning a carb. And the last few days with the impending storm have been no better.

 

[Pmt133]

So I got out. Picked up 100 RPM up top compared to when I started. Long and short I pretty much ended up back where I started... which makes sense. I found a vacuum leak on the base today and because of that installed the "thick" edelbrock base plate gasket/4 hole spacer.

My final tune up was .092 primary .095 secondary with the 65/57 metering rod. Snap is back, no lean spots either. cruise reads on the plugs came back good enough. AFR reading 13-13.5. Drops to 12.8 when the step up spring hits the power side and then drops pretty low when the secondary opens. Comes up to an even 12 at wide open which is safe. being it was in the 90s today those will lean out a tad at cooler temps but nothing scary.

I think (big word there) I can jet down the secondary one more size to a .092 as well and go to a 63/47 metering rod and be perfect. That would fatten up the cruise slightly and power on the rod a bit, but take it out of the dump when the secondary starts doing it's thing.... Decisions.

Edit: I am starting to understand why merc used a 3 step rod lol

 

[Scott06]

So I got out. Picked up 100 RPM up top compared to when I started. Long and short I pretty much ended up back where I started... which makes sense. I found a vacuum leak on the base today and because of that installed the "thick" edelbrock base plate gasket/4 hole spacer.

My final tune up was .092 primary .095 secondary with the 65/57 metering rod. Snap is back, no lean spots either. cruise reads on the plugs came back good enough. AFR reading 13-13.5. Drops to 12.8 when the step up spring hits the power side and then drops pretty low when the secondary opens. Comes up to an even 12 at wide open which is safe. being it was in the 90s today those will lean out a tad at cooler temps but nothing scary.

I think (big word there) I can jet down the secondary one more size to a .092 as well and go to a 63/47 metering rod and be perfect. That would fatten up the cruise slightly and power on the rod a bit, but take it out of the dump when the secondary starts doing it's thing.... Decisions.

Edit: I am starting to understand why merc used a 3 step rod lol

I found the same thing with the base gasket. Your edlebrock has the same square and spread bore mounting that my intake does. There is very little sealing surface in a couple spots on the secondary side with webber/eddy carbs. I found this when installing a phenolic insulating spacer. The thicker gasket is a good idea here.

 

[Pmt133]

I found the same thing with the base gasket. Your edlebrock has the same square and spread bore mounting that my intake does. There is very little sealing surface in a couple spots on the secondary side with webber/eddy carbs. I found this when installing a phenolic insulating spacer. The thicker gasket is a good idea here.

I agree. It was cheap and I figured it wouldn't hurt after finding a substantial leak.

Now if I could just figure out my idle lol. Basically needs the idle screw all the way out and mixture screws a tad lean. (Mild surges. About 2 turns out each.) I'm wondering if when I did the throttle plates I installed them off slightly and they are hanging up in the bores. I'll have to look closer and or check for other vacuum leaks. What I am finding is for the idle mix to read right on the plug it idles around 800. To get 650 it reads a little lean on the plug and the meter confirms.

 

[nola mike]

I agree. It was cheap and I figured it wouldn't hurt after finding a substantial leak.

Now if I could just figure out my idle lol. Basically needs the idle screw all the way out and mixture screws a tad lean. (Mild surges. About 2 turns out each.) I'm wondering if when I did the throttle plates I installed them off slightly and they are hanging up in the bores. I'll have to look closer and or check for other vacuum leaks. What I am finding is for the idle mix to read right on the plug it idles around 800. To get 650 it reads a little lean on the plug and the meter confirms.

I would think that was long as you're not hesitating off idle you're good. I hear you with the winds... Looks like I might not get in this weekend again, even though the damn boat was ready earlier than in years.

 

[Scott06]

Now if I could just figure out my idle lol. Basically needs the idle screw all the way out and mixture screws a tad lean. (Mild surges. About 2 turns out each.) I'm wondering if when I did the throttle plates I installed them off slightly and they are hanging up in the bores. I'll have to look closer and or check for other vacuum leaks. What I am finding is for the idle mix to read right on the plug it idles around 800. To get 650 it reads a little lean on the plug and the meter confirms.

one or both throttle plates may be upside down and not closing.

Are you setting idle speed with the throttle cable disconnected? Are the throttle blades exposing the transfer slot? This could add fuel that the mix screw will not control. normally this is seen on hot rod engines with big cams that you turn idle speed screw in to get more air flow, then cant control the fuel, but could be happening here.

Bottom line if the idle speed cant be set lower than 800 with out leaning the crap out of it something is wrong. WOuld def look at throttle plates and linakge to see if its getting hung up.

 

[Pmt133]

It's not incredibly lean... 15.5 or so. But if I run her down to 14 I get 7-800.

Linkage off, base idle mode (thunderbolt V) and adjust idle. Then adjust mixture then back to idle. I think I'll double check the throttle blades and transfer slot and try and sniff out a vacuum leak again. I'm about 2 turns out on the idle mixture for good idle and no stumbles. On very, very light tip in it stumbles a tad... im talking idle to about 1200 rpm slowly. But otherwise if you drop the hammer from idle it just goes.

Oh and @nola mike I have basically ended up at ricks adjustment. But have the primary and secondary jets flipped. I am a convert though... I've run holleys forever. This weber (mines an actual mercury/weber) is crazy simple to tune. I wouldn't dare touch a jet on the water on a holley. Yes you can dial in a holley better but between fine tuning with step up rods and springs you can get close and only have to swap rods... it's pretty amazing.

Edit: another thought. I drilled this carb for an electric choke... is it possible I have a small vacuum leak in the coil housing on the pull off?

 

[Scott06]

Oh and @nola mike I have basically ended up at ricks adjustment. But have the primary and secondary jets flipped. I am a convert though... I've run holleys forever. This weber (mines an actual mercury/weber) is crazy simple to tune. I wouldn't dare touch a jet on the water on a holley. Yes you can dial in a holley better but between fine tuning with step up rods and springs you can get close and only have to swap rods... it's pretty amazing.

Edit: another thought. I drilled this carb for an electric choke... is it possible I have a small vacuum leak in the coil housing on the pull off?

Yeah all these carbs (Holley, AFB/Eddy, Q-jet, Rochester 2 jet) have their pluses and minuses. I have also found on both my 65 Pontiac and the boat the AFB/Weber/Eddy carbs to be really a great carb for ease of use and tuneability , especially for less experienced tuners. Anyone who tells you Carb X sucks use carb Y etc is FOS. Ultimately if you know what you are doing some of the high end Holley variants have the most tuneability in terms of multiple replaceable air belleds etc, but what we are doing here on a low rpm marine engine is pretty simple and this is uneeded.

Yes you may have a vacuum leak on the choke mods. Spray starting fluid or use an unlit propane torch to see if it gets sucked in, idle will change or rpm will pick up. Usually if you have a vacuum leak you will need more than 2 turns out though.