Edelbrock 1409 tuning and plug reading

[Scott06]

Attached is a photo of my spark plugs, not sure if these are ok or a tad lean, any advice is appreciated.

They are off my 5.0 Vortec that I repowered (21 ft Sea Ray 200 Sport, previous owner cracked original 4.3). Has a Michigan Motorz partial engine package including 1409 carb, cast iron 4 bbl intake ( allegedly a cast iron copy of Edelbrock performer- they grind the manufacturers name of them), thunder bolt v ignition.

Originally the plugs looked lean- almost white. I swapped the stock metering rods for a .065 X .037, put in the pink 7" metering rod spring, and the .33 accelerator pump nozzle (thanks Rick). The metering rods should be 1&1/2 stages richer on cruise mode, 2 stages richer in power mode. Acceptor pump nozzle really smoothed out the off idle bog when hitting WOT holeshot. FWIW I'm running a 5.0 Gen+ igntion module 10 deg base, total advance seems to be about 26 deg at 3800 rpm.

No real performance issues, pulls hard when tubing, skiing, or wakeboarding even with 7 people in the boat. Lugs a little bit when I make a quick turnaround to pick up a skier in the water, warm restarts after sitting are slow some times. I just not sure if I'm rich enough, haven't heard any detonation. What do you guys think of how the plugs read? Any advice on this, the lugging, and restarts would be appreciated.

Thanks

 

[NHGuy]

Best thing you can do is print out the carb tuning section of the Edelbrock carb manual. It instructs you to time some acceleration runs and make changes based on timing your rpm sweep. Also print out the page for the 1409 carburetor. It will give you everything you need to properly set up the carb. You do the primary side first then the secondary.

Your plugs look pretty white to me. But their appearance means little unless you run them to your desired rpm and then just shut off the engine like the old days. Then they would show condition at load and rpm.

As far as the lugging to pick up a skier in a slow turn, try going back to the original orange springs that came in the carb. If it's better good, if its worse go for more spring.
It's an inverse relationship. When the engine vacuum is high the rods get sucked down where their fat ends restrict the fuel to the primary venturis.
So you could be getting a rich bog with the stronger springs. Conversely: If it pops (lean) you'd probably use a stronger spring to add fuel.
There is nothing to compare to since you are working with different jets and springs. It's trial and error. But fun!

BTW my 350 mag came with dinky secondary .092" jets. But when I put the carburetor on my 383 I went to .098" on them. The .101's that came with your 1409 might leave your engine a little fat. So do the timed tests.
I left the oe primaries as they were at this point cause it's running well and every time I have gone to time the boat something has interfered.

For some reason the Thunderbolt V engines make more power with less jet. But they do use the stronger metering springs. I think it's the mean best timing finding max efficiency combined with different cam profiles.

 

[Bondo]

I just not sure if I'm rich enough,

Ayuh,..... They look to white to me too,..... Here's a link to the AFB carb Bible,....

 

[Rick Stephens]

NHGuy gave a perfect post on springs. Softer the spring, leaner it runs when you increase throttle. Stronger spring opposes the vacuum that pulls the piston down.

I like to set springs so that when I gently hand throttle up, at the carb with the cable disconnected, I want to see the needle pistons lift up momentarily to richren mixture then drop right back down so I am running on the main jetting. The needles are then activated based on how much vacuum I drop during a throttling up. They don't really do anything else.

Your plugs look lean. I like tan, not white. Hard to tell though unless you do a sustained run at a given throttle then shut down and pull a plug. Do that at several throttle settings to fine tune.

 

[Scott06]

Gents,

Thanks for confirming I'm on the lean side. I'll fatten it up another notch, try another spring and see where it goes.

I didn't consider stopping immediately and pulling a plug or two, since I have to idle through a shallow cove into the dock, I may just be seeing the idle mixture.

NH the 1409 comes with .098 primary jets, .101s are in the secondaries so a tad leaner out of the box.

Thanks

 

[Scott06]

Hey foks,

still chipping away away at this. Here's what I've done so far

primary left in the .089 jets, using .063 x .037 step up rod, went back to orange spring from pink.
accelrator pump using nozzle .043 on middle hole
secodnaries went one step richer to .104

i have a couple stumbles between 3400 and 4200 rpm when at full throttle acceleration. Runs perfect without hesitation at all lower than wide open throttle acceleration.

Plugs look a tad on rich side, but I'm not sure wether I should lean out secondaries or step up rods. Does any body have a feel for what rpm a 1409 will start to kick in the secondaries on a 5.0 vortec head stock engine (only aftermarket items are carb Andy Michigan motorz cast iron intake)? Also where do you think the step up rods would go rich ? I assume this is more throttle opening Andy thus vacuum than rpm related?

Thanks

 

[Rick Stephens]

I could pretty easily hear the secondaries opening. But you might have someone watch for you, ease into the throttle until you are wide open primaries and just before secondaries. Should be able to see that in the linkage, I think. Then do a 5 minute run and shut down. Look at the middle plugs, they seem the leanest. This lets you zone in the main jets.

After finishing up with calibrating mains you might find the secondaries are just fine.

 

[NHGuy]

Under full throttle you have very little vacuum. Your rods are probably fully extended in that circumstance. Also rods are easier to swap than jets are. So record what you have and try some thicker ones to lean out the rod contribution. If it gets worse go the other way a step. If it's still bad go back to where you were and adjust your secondary jets first the same ways. First a step lean ,then two steps rich. If it's still bad go back to the baseline and start changing your primary jets.
It's a bracketing thing.
Get yourself a good notebook and record stuff. Also get a power screwdriver to remove and reinstall the carburetor torx bolts. Otherwise you'll be all day. Be careful, don't drop those bolts!

 

[Leardriver]

I have operated a dyno for years with 4 stroke dirt bikes. You just can't get a read on plugs with modern fuel and additives.
You have to do a high rpm run with a plug chop and engine switched off. A challenge on boats.
It is worth a fortune to tune with a wide band O2 sensor, even if you have to drill a hole in the exhaust and fill it with a plug afterwards.

 

[NHGuy]

So true Leardriver!

 

[Scott06]

Gents,

thanks for your replys . Sorry for late reply, work has been a bit busy this week. Below are photos of plug reading before I made changes this weekend

To me these looked leanish but I leaned out my step up rods to a .65x.42. Stumble between 3-4 k rpm went away, had a touch of stumble at 4200, suspect I need to lean out secondaries.

Per comments on secondary opening, I guess I need to rn with dog house and flame arrestor off to see what the air valve above secondaries is doing at a given rpm.

I had looked into the air fuel ratio meter, just didn't pull the trigger. There's some sandwich plates available to put an o2 meter between the exhaust manifold and elbow, does anybody have experience with the meters and can comment which will work well? Agreed this would be best to tune it in.

 

[Scott06]

So I think I'm getting to the end of my process here. Went back to the factory .101 secondary jets and that got rid of my stumble at 4200. So in the end I just went one step richer on the step up rods, and the largest pump nozzle. I may end up trying one accelerator pump lever position leaner, but very close now.

I would second the comments on te O2 meter as by looking at the plugs I wouldn't have thought I'm too rich.

Thanks for your help

 

[Rick Stephens]

Would love to have that tool in my box. I did it the barbarian way though. Pulled the plugs a doze times.

Glad you're getting there.

Rick

 

[406Maverick]

So I think I'm getting to the end of my process here. Went back to the factory .101 secondary jets and that got rid of my stumble at 4200. So in the end I just went one step richer on the step up rods, and the largest pump nozzle. I may end up trying one accelerator pump lever position leaner, but very close now.

I would second the comments on te O2 meter as by looking at the plugs I wouldn't have thought I'm too rich.

Thanks for your help

Hello there, I know it's been a while since this thread was updated, but since I have the exact setup you have I'm hoping by now maybe you have got er dialed in..? I just started a new thread but am hoping to hear from you directly as well