Running lean after engine swap

nola mike

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I would pull the end cover off the carter fuel pump and look at the vanes. you could have debris in one of them, thus the low output pressure.

something is taking your pumps out.

The first pump was too high output. This one I checked before running it, off a jerry can.
Fun fact though. I noticed that michigan motorz is selling my setup (newer 4.3 with 1409). I called to ask about their jetting. They said they run the 1409 straight out of the box. I've been on hold with Edelbrock for an hour now to try to get in touch with their tech support...
 

nola mike

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So Edelbrock tech support seems to think that the single plane manifold is the culprit, though I wasn't really able to follow his reasoning. Basically that the fuel wasn't atomizing properly, and that I'll have to run richer to compensate. Wish I had known more about this stuff before I bought it, but a new one isn't in the cards this year for sure. But he also thinks that I can compensate for it.

Has anyone tried doing this using a vacuum gauge? I think it would be helpful to know exactly where I am in the power v cruise metering.
 

kenny nunez

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It appears that reversion is the problem. With a vacuum gauge that you can watch you will probably see a point where the reversion is causing the vacuum to “0” out and cause what is known as fuel frothem or standoff. Are you using the original outdrive with the 1.84 or 1.65 ratio? I wonder what would happen if you went down on propeller pitch to get past the reversion spot.
 

nola mike

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Alright, digging deeper into this. I bought a manifold replacement for the oem Merc reman engines, 824330T1, like this one. Looked like single plane to me, but after more reading I don't know. Also looks spread bore. However, this combo should be the same as stock Merc with the weber so should work fine, unless I'm missing something. (Merc setup also doesn't use an adapter plate).
 

nola mike

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Pretty sure the manifold I have is dual plane after doing more research. Tested with 5mmhg springs and .065x047 rods. Put a vacuum gauge on it today, solid 20 mmhg at idle. At 2500 rpm I'm at 10mm, 3200rpm around 5mm. I didn't get to play as much as I wanted today, but this indicated that 2500 rpm should be strictly in the cruise setting of the rods. So I did a run at 2500 rpm, and the plugs look identical. Very strange. After the run though, the engine wanted to diesel when I tried to shut it down. Took 3 or 4 attempts before it cut off. That's the first time that's happened. Leads me to think maybe I am richening up? But idk why the plugs are still reading lean.

Next weekend I'm going to get some longer vacuum hose so that I can get some real time vacuum measurements (the gauge was in the doghouse), and I guess the next step is to try .063x.047 rods at 2500 rpm, then maybe 3300 rpm (right before secondaries open), which should be my power mode. Then I'll do one in the middle and change the springs to adjust the mix in the range. Sound like a plan?
 

Rick Stephens

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You just did a long cruise with a load of people on board. If you heard no pinging at all things are better than really lean.
 

nola mike

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Yeah, that and the dieseling makes me think I'm rich now, but the plugs look the same as when I was backfiring? See pics...
 

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Rick Stephens

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I’m with you there. I just did a 100 mile cruise. This makes me want to pull and look at a couple plugs and see what mine look like. Hven’t done that this year....
 

nola mike

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I’m with you there. I just did a 100 mile cruise. This makes me want to pull and look at a couple plugs and see what mine look like. Hven’t done that this year....

I'm curious what they look like. Agreed mine don't look too different though, right? I need a damn o2 sensor.
 

nola mike

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More I'm reading about this, the more I'm thinking that I may be a) reading my plugs wrong, and/or b) needing a fresh set of plugs every time I do a plug chop. A lot on the internets are saying that the chop is only good with fresh plugs, and that a tan insulator tip isn't necessarily where I should be looking; that I need to be looking farther down the insulator. As long as the tip isn't snow white I'm ok?
Here's a representative article:
https://www.hotrod.com/articles/spark-plug-reading-101-dont-leave-hp-table/
 

Rick Stephens

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Good article. More than I ever knew, or considered. I will pull a couple plugs, have to find time. Is about the right time here to think about winterizing. Already had a few nights in very low thirties.
 

Scott06

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https://enginebasics.com/Engine Basics Root Folder/Reading Spark Plugs.html

this is a pretty good article on plug reading, read the section on mixture, basically reading around the plug base ring, different than I had done in the past. When I tuned my 5.0 and 1409 plugs looked lean to me actually a lot like yours so I went richer and ended up with stumbles until I leaned it out. Ended up basically that out of the box it worked pretty well except I went owing a bigger accelerator pump nozzle and one step richer metering rods. Leaving the plugs in a whole season they look at tad rich which is what I was shooting for ...
 

nola mike

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https://enginebasics.com/Engine Basics Root Folder/Reading Spark Plugs.html

this is a pretty good article on plug reading, read the section on mixture, basically reading around the plug base ring, different than I had done in the past. When I tuned my 5.0 and 1409 plugs looked lean to me actually a lot like yours so I went richer and ended up with stumbles until I leaned it out. Ended up basically that out of the box it worked pretty well except I went owing a bigger accelerator pump nozzle and one step richer metering rods. Leaving the plugs in a whole season they look at tad rich which is what I was shooting for ...

Yup, I actually saw both that article and your thread. Looked like you just said screw it and tuned to how it ran rather than plug reads. Seemed like you did the same thing I'm doing now.
 

Scott06

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Yup, I actually saw both that article and your thread. Looked like you just said screw it and tuned to how it ran rather than plug reads. Seemed like you did the same thing I'm doing now.

It’s not screw it, I just think you have to run the plugs longer to get a read. My plugs looked clean like yours but after a year they look like attached
 

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nola mike

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But that's completely against the idea of doing a plug chop--you're trying to get a read on mixture at a specific rpm/load. And unless you're really at the extremes for a long time across all ranges, I'm not sure how accurate plug reading is.
 

Rick Stephens

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nola mike Scott06

I'll have to concur with Scott as well. I put new plugs in start of this season. Last time I ran the motor it was for a 100 mile cruise up and back all at midrange 35-38 MPH. As I mentioned earlier, I wanted to pull a plug and just see what they look like. Kind of just like Scott's.

I was surprised to see one side with more color than the other. Vortec plugs come in from the side though, so must be hotter facing the piston.

Sorry about the focus, bright day here, couldn't see the screen at all, easy to get the idea though.
Click image for larger version  Name:	plug.jpg Views:	1 Size:	54.9 KB ID:	10935642
 

nola mike

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Rick Stephens , I gotta say that all of these plugs look pretty similar. I didn't see much of a change between running clearly lean and backfiring and my last read. Certainly none had that tan color uniformly, which is what I was expecting. All 3 of us have a plug that's pretty white with a small tan stripe. I bet most would look at all 3 of our plugs and say they're lean, particularly if you don't see the tan stripe. Look at Scott06 middle pic. Looks white. What I've been reading is that the magic color doesn't happen at the insulator tip. I'm going to go completely stock next time out and start over. Been raining the last 2 weekends here, hopefully tomorrow.
 

nola mike

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I was planning on swapping in the stock rods on the water, but didn't have the torx bits in toolbox #3 🙄

So used the .065x047 rods as before. I pulled plugs after 12 miles of running mostly at 35 mph. My tach is off (going to leave details in my swap thread) so not sure of rpms but it ran great across the board.
had the vacuum gauge connected the whole time, and it was interesting.

--in general, the vacuum slowly decreases with speed --it drops briefly into the power zone (<5mmhg) when I hit the throttle, but then recovers
-- @30 mph I'm at 10mm
--35 mph 8 mm
--42 mph 5mm

So basically I'm in cruise mode when under a steady load for most of my normal cruising speeds. I was lightly loaded today, just me and the kids.

Big problem? Top end. I only hit 45-46 mph unknown rpm (tach said 3600). 40-42 it gets to with no drama at all, maybe Âľ throttle, doesn't feel like it's working hard at all. After that, much more noise but not much speed. For perspective, my 470 hit 48-49 when I first got it, and last year still got to 46-47 when it was a tired engine.

IMG_20200927_142501.jpg

IMG_20200927_142508.jpg
IMG_20200927_142514.jpg
 
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Rick Stephens

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I've noticed the same throttle behavior on my setup. Opening secondaries a little gives more power and speed, opening them more gives more noise without a lot of speed or noticeable power increase. You and I might need to address mixtures in the secondaries, I'm not sure whether we are lean or rich though. I'm almost inclined to think the 4.3L can't use 600 CFM.
 

nola mike

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Possibly, but the secondaries are opened by air flow through the carb, right? So if they're opening, the engine should need the air? And that doesn't explain why I'm missing 50 hp of top end power...
dunno if the mixture can be off enough to do that while still running correctly. I'm terrified to lean out my secondaries and do wot runs
 
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