Running lean after engine swap

[Scott06]

Yes a 4.3 cannot use all 600 cfm would be interesting to see how far the air flap On the secondaries opens at wot.

mike I’d get the tach straightened out before you lose sleep on the top end. The 4.3 should be able to rev higher than the 3.7 did up to like 4800-5000. See where u are at wot rpm.

also I would think the 4.3 added some weight vs the 3.7 you mention 50 hp this has vortex heads with the 8 bolt intake? What was the hp on the orig8nal 3.7, have you checked that you are getting full ignition advance ? By like 3 k rpms you should have 22-26 degrees total. I think a stock 190 hp vortec 4.3 with Tbolt ignition had 8 deg Initial and 16 degrees advance off the module.

 

[nola mike]

Original 3.7 was 170 hp at the crank. I should be in the 220 range, yes vortec heads. Haven't checked total advance yet. I thought about the extra weight. I think I should only be 200# more. My buddy has a VP 4.3 efi in a boat double the weight of mine that hits 45. I should do better... At least it sounds super cool when the secondaries open. My wife is totally impressed :sleeping:

 

[Scott06]

My wife is totally impressed :sleeping:

I assume you’ve been married for more than a few years like me... Well if you have that who cares how fast then.

 

[Scott Danforth]

My wife yells "slow down" a lot.....

 

[nola mike]

My wife yells "slow down" a lot.....

Huh. Mine always says hurry up. And this thread is about to go off the rails. In other news, ordered a trailer hitch for the new tow vehicle, '17 golf sportwagen

 

[Scott Danforth]

cool, dad had an '09 Jetta Sportwagen TDI with the panoramic roof. he pulled the little fishing boat all over creation. car had over 309k on it when I sold it for the estate.

 

[nola mike]

Luckily it's only ½ mile to the ramp (shhhh, don't tell VW). Other notable tow vehicles for this boat have included a Mazda 6 wagon, bmw 330 convertible, and porsche boxster s (which was ridiculous). Think I'm going to hold off using the mini if possible

 

[Scott06]

Luckily it's only ½ mile to the ramp (shhhh, don't tell VW). Other notable tow vehicles for this boat have included a Mazda 6 wagon, bmw 330 convertible, and porsche boxster s (which was ridiculous). Think I'm going to hold off using the mini if possible

Glad to hear I’m not the only one who uses the run what you brung towing philosophy. My dad and I used tow Both my 17 ft sea ray and his 22 ft Catalina 22 with my grandfathers Volvo 240 and his accord coupe... and the accord had 265 k miles. My brother and I had to sit on the front fenders once to hook up when the ramp was wet and slimey...

 

[nola mike]

Glad to hear I’m not the only one who uses the run what you brung towing philosophy. My dad and I used tow Both my 17 ft sea ray and his 22 ft Catalina 22 with my grandfathers Volvo 240 and his accord coupe... and the accord had 265 k miles. My brother and I had to sit on the front fenders once to hook up when the ramp was wet and slimey...

The bimmer had 230k when I sold it last year. Rwd and traction control and 225hp actually made it pretty easy to get the boat out of the water.

 

[nola mike]

Ok, another update.

Got my cheap digital tach working, and came up with these numbers:

3200 rpm / 32 mph / 11 mmhg

3500 rpm / 36 mph / 7 mmhg

4k /42 mph / 5-6 mmhg

Wot 4500 rpm / 4-5 mmhg

I thought I heard it ping a couple of times at wot. I'm going to fatten up the secondary jets and see if that makes a difference in the top end.



Another weird thing is that after running 35 miles without issue, I go to trailer the boat. Like last time out it starts to sputter and run rough. Got it out and on muffs and it looks like the carb is flooding again. Didn't deal with it that night, but when I fired it up in the morning it ran fine. Any ideas?



Lastly, checked my plugs. Definitely more tan, but this was after the carb was running flooded for a few minutes. Unusual thing is that the #5 and 6 plugs still looked the same, for sure lighter (I had only been pulling #5 before, so don't know what color the others were prior).

 

[Rick Stephens]

I'd worry less. If you were pre-igniting it would blast all those deposits right off. Go ahead and try a little richer secondaries, but don't worry so much.

 

[nola mike]

@Rick Stephens Worrying less now, working on tuning. Might have imagined it anyways. Those plug pulls were actually from last time out, which was a similar run with flooding at the end. I'm still a step lean on the secondaries from stock. I could also try some stiffer springs, which would get me into the richer part of the rods at WOT. I'm still not making the power I should be I don't think.

What do you think about the flooding? It's happened last 2 long runs right at the end. Last time I couldn't find anything wrong and it fixed itself. Fixed itself this time as well apparently.

 

[Rick Stephens]

I don't know. Not had any issue with flooding at end of a run or after parking. Have had the motor seem to load up once in a great while. A little extra throttle for a few seconds seems to clear it up.

 

[Scott06]

I think you are fine now and don’t need to go richer. I was at the same spot and put one step richer secondary jets in and got a stumble 3400- k .These guys use The ring around the base to tell jetting that tells me you are rich enough

Reading spark plugs | Tuning Spark Plugs

How to read spark plugs for rich/lean conditions with tuning tips for dialing in fueling for max power and better combustion without burning up a piston

enginebasics.com

youre already into the richer part of the secondaries at the vacuum levels you list there a stiffer spring will only make go rich earlier (at a higher vacuum) basically may go rich at like 2500 rpm vs 3000 rpm.
what’s your total advance at 2800 rpm or so ? I think a vortec 4.3 wants 24 degrees total. i think you might Want to drop 2” in pitch and you should hit 4800-4900 rpm . What prop u running ? How much can you trim it out.
I had a situation where I get best top speed with a 4 blade Revolution 4 because I can trim it all the way out to trim limit let’s engine get another 300 rpm.
what Intake did you land on ? I recall some question if you had a single or dual plan right?
on the flooding what makes you think you are flooding ? I did have a hot restart issue on after sitting I think fuel dribbled out into intake emptying float bowl. Seems to restart better if you opened the throttle to air it out so to speak...black exhaust...

 

[nola mike]

youre already into the richer part of the secondaries at the vacuum levels you list there a stiffer spring will only make go rich earlier (at a higher vacuum) basically may go rich at like 2500 rpm vs 3000 rpm.

I'm running the stock 5 mmhg spring. So it's not getting rich until nearly WOT.

what’s your total advance at 2800 rpm or so ? I think a vortec 4.3 wants 24 degrees total. i think you might Want to drop 2” in pitch and you should hit 4800-4900 rpm . What prop u running ? How much can you trim it out.

Haven't checked the advance. I'm running the exact same prop and drive that I had on my 3.7. With better compression and 50 more hp, I should be doing better. Trim is the same, though it doesn't feel like I'm able to trim as much. Could be the extra weight in the back. IDK that the 200# should make that big of a difference in top end, but who knows.

what Intake did you land on ? I recall some question if you had a single or dual plan right?

Yeah, I did. It's a dual plane, stock GM cast intake. That was my misunderstanding.

on the flooding what makes you think you are flooding ? I did have a hot restart issue on after sitting I think fuel dribbled out into intake emptying float bowl. Seems to restart better if you opened the throttle to air it out so to speak...black exhaust...

I saw fuel dribbling down 1 venturi, though the butterfly was cracked and I was at 900 rpm. It wouldn't idle with the throttle closed. Ignition related shouldn't be running fine at 4k rpm and then start missing at idle.

 

[Rick Stephens]

I'm running the stock 5 mmhg spring. So it's not getting rich until nearly WOT.

The springs work against vacuum. When you open the throttle up vacuum goes down - quickly. The springs hold the needles up when the vacuum decreases just a little bit, the springs are pulled down when running first quarter of the throttle after initial drop in vacuum, then vacuum goes up and sucks the needles back down. They are sensitive at lower throttle openings, totally ineffective at more open throttle settings. Once you get the throttle open even 1/2 of the way on primaries your vacuum drops and the springs hold the needles up all the time. Once you are on secondaries you always have primaries at max flow since the springs hold the needles all the way up and out and vacuum is basically nonexistent..

 

[nola mike]

Once you get the throttle open even 1/2 of the way on primaries your vacuum drops and the springs hold the needles up all the time. Once you are on secondaries you always have primaries at max flow since the springs hold the needles all the way up and out and vacuum is basically nonexistent..

That's not my understanding of how the system works. You want to be running in cruise mode unless under moderate part acceleration, when vacuum drops and you get into the power section of the rods. The spring strength (which is in inhg, realized I've been saying mm) determines at what vacuum you transition to the power mode. In my case I'm running 5" springs. When I'm not accelerating my manifold pressure doesn't hit 5" until nearly wot, so my rods are down until then.

 

[Scott06]

I'm running the stock 5 mmhg spring. So it's not getting rich until nearly WOT.



Haven't checked the advance.

check your advance is all in. Easy way to rule out the simple Things. If you don’t have full advance you will not actually have the 50 Extra hp You thought you were getting by this swap.

I'm running the exact same prop and drive that I had on my 3.7. With better compression and 50 more hp, I should be doing better. Trim is the same, though it doesn't feel like I'm able to trim as much. Could be the extra weight in the back. IDK that the 200# should make that big of a difference in top end, but who knows.

200 would make a diff what prop and pitch? Black max ? what’s your slip

Yeah, I did. It's a dual plane, stock GM cast intake. That was my misunderstanding.


I saw fuel dribbling down 1 venturi, though the butterfly was cracked and I was at 900 rpm. It wouldn't idle with the throttle closed. Ignition related shouldn't be running fine at 4k rpm and then start missing at idle.

maybe but I would expect to see the mains start dribbling fuel at 900 rpm. I’ve seen that on mine at least close to 1 k rpm and it idles fine.

yes the step up springs are measured in inches not mm of hg How are you measuring that I’d be surprised if with a carb that big on that engine you’d be pulling 5” of vacuum . Either way the plugs read in my opinion fine at wot. you can try richer Secondaries or stiffer primary step up springs but I think youlll get a stumble being too rich 4 k ish

the fact that you can Not hit 5 k rpm makes me think you aren’t getting full ignition advance , which is why I keep bringing it up.
In a boat that light you should be able to hit Max rpm unless you have Like a 23 pitch. Possible the 3.7 made more torque but I doubt it’s the 4,3 is pretty good in that dept as well.

 

[nola mike]

check your advance is all in. Easy way to rule out the simple Things. If you don’t have full advance you will not actually have the 50 Extra hp You thought you were getting by this swap.

Heh, hard when you're the only one on board. But yes, worth checking.

200 would make a diff what prop and pitch? Black max ? what’s your slip

23p, quicksilver al.

maybe but I would expect to see the mains start dribbling fuel at 900 rpm. I’ve seen that on mine at least close to 1 k rpm and it idles fine.

I'll have to check when it's idling ok to see what's going on. I may be on the wrong track, but i can't figure what else would cause this particular idle issue. It also doesn't seem to clear when I rev it. I'll probably need to play with it on the water instead of in the driveway if it happens again.

yes the step up springs are measured in inches not mm of hg How are you measuring that I’d be surprised if with a carb that big on that engine you’d be pulling 5” of vacuum . Either way the plugs read in my opinion fine at wot. you can try richer Secondaries or stiffer primary step up springs but I think youlll get a stumble being too rich 4 k ish

the fact that you can Not hit 5 k rpm makes me think you aren’t getting full ignition advance , which is why I keep bringing it up.
In a boat that light you should be able to hit Max rpm unless you have Like a 23 pitch. Possible the 3.7 made more torque but I doubt it’s the 4,3 is pretty good in that dept as well.

I'll check the advance. That last read wasn't a chop, so I don't know that you can draw any conclusions about my mixture at any specific point. I'm measuring vacuum off of my intake manifold. I'll swap out the secondary jets and see what happens. If I don't improve my top end or I stumble maybe I try a step leaner.

 

[Scott06]

Heh, hard when you're the only one on board. But yes, worth checking.

you can check it Dock side as you don’t need to be moving. Just get the roms above 3 k or so In neutral. You need an advance timing light or a timing tape on the balancer.

23p, quicksilver al.

thats about 16-17 % slip which is expected for what you are running. If you c@nt trim it out as much that that makes me think you are now more stern heavy keeping more of the hull in the water, and maybe a prop With more bite will allow mor trim to get hull out of the water.that worked for my sea ray 200 which is a$$ heavy .

I'll have to check when it's idling ok to see what's going on. I may be on the wrong track, but i can't figure what else would cause this particular idle issue. It also doesn't seem to clear when I rev it. I'll probably need to play with it on the water instead of in the driveway if it happens again.


I'll check the advance. That last read wasn't a chop, so I don't know that you can draw any conclusions about my mixture at any specific point. I'm measuring vacuum off of my intake manifold. I'll swap out the secondary jets and see what happens. If I don't improve my top end or I stumble maybe I try a step leaner.

I think both rick and I had the same conclusion on chop plug readings was tough to get a true read.take this for what it’s worth - Your plugs look similar to mine which are a couple of seasons in, I get inconsistent brown around the insulator like Rick mentioned. Bottom line I use my boat pretty hard in terms of load and water sports and have five years Post repower with no issues , so I don’t think you are in danger lean territory