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L18 8.1L swap resource thread

SpeedlabDan said:
So i got the howell harness for my build and the only issues other than some odd lengths are the knock sensor plugs. Im usingvthe knock semsors you have listed but i cant locate a pigtail to fit them. Thr connections on the harness are a small two pin utilized only one pin. The semsotd are somewhat round but with a clip spuke to pne side. Noy the typical round style. Any ideas?
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Picture of the connector on the harness or of the knock sensor?

This is the connector that is usually used:
https://www.rockauto.com/en/parts/acdelco,PT1428,knock+/+detonation+sensor+connector,13326

But it can be this one:
https://www.oreillyauto.com/detail/...l-a-c-compressor-connector/s550/5820198?pos=9
 
SpeedlabDan said:
Took me a couple days to remember to take a pic with the rest of the tasks goin but here's the plug that came for my knock sensors @Larry @bigblock72
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Yep, they gave you the wrong connector for the knock part numbers in this thread, or mislabed that truck of harness. Are you sure that is the knock sensor? Either you have to research what knock sensors fit that and hope they thread in the block, call them and tell them you need the round Knock sensor connector and they send it to you or cut them off and add a pair of PT308 connectors to match the 213-2829 (Pass) and 213-298 (Drivers) knock sensors, which is what I would do as I always felt their knock sensor leads were too short anyway. I routed the knock sensor wires over the front of the block on the Suburban to keep them out of the heat of the exhaust manifolds. On the K10, they route on the back side of the engine where they make me nervous how close to the exhaust manifolds they run.

PT308
PT308_Primary.jpg
 
Larry said:
Yep, they gave you the wrong connector for the knock part numbers in this thread, or mislabed that truck of harness. Are you sure that is the knock sensor? Either you have to research what knock sensors fit that and hope they thread in the block, call them and tell them you need the round Knock sensor connector and they send it to you or cut them off and add a pair of PT308 connectors to match the 213-2829 (Pass) and 213-298 (Drivers) knock sensors, which is what I would do as I always felt their knock sensor leads were too short anyway. I routed the knock sensor wires over the front of the block on the Suburban to keep them out of the heat of the exhaust manifolds. On the K10, they route on the back side of the engine where they make me nervous how close to the exhaust manifolds they run.

PT308
PT308_Primary.jpg
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I felt they were short as well. I am running the knock sensors that you have listed. However I can't tell for sure if they aren't the ones that @bigblock72 listed
 
SpeedlabDan said:
I felt they were short as well. I am running the knock sensors that you have listed. However I can't tell for sure if they aren't the ones that @bigblock72 listed
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If you are running the sensors Larry recommended then you will need the PT308 pigtails, which is the second pigtail that I linked and should be super easy to find.

The connector on your harness fits 08ish and newer LS motors, I have no idea why they would put them on a 8.1 harness.:dunno:
 
bigblock72 said:
If you are running the sensors Larry recommended then you will need the PT308 pigtails, which is the second pigtail that I linked and should be super easy to find.

The connector on your harness fits 08ish and newer LS motors, I have no idea why they would put them on a 8.1 harness.:dunno:
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I'm calling them in a few
 
Hey so I got my 8.1L running and aside from some issues with the fuel level and oil psi with the dakota dash it idles fine. Under power its gutless. It's my suspicion my fuel psi may be down and I plan on checking it tomorrow at the rail. If I can adjust the regulator, do you have a procedure? I'm using an ep381 pump so I feel the problem may be in pressure at the rail? For now I'm scratching my head but once I test the psi maybe I can tune it in. It is a 2001 so I imagine it's adjustable but looks like a closed/fixed regulator.
 
SpeedlabDan said:
Hey so I got my 8.1L running and aside from some issues with the fuel level and oil psi with the dakota dash it idles fine. Under power its gutless. It's my suspicion my fuel psi may be down and I plan on checking it tomorrow at the rail. If I can adjust the regulator, do you have a procedure? I'm using an ep381 pump so I feel the problem may be in pressure at the rail? For now I'm scratching my head but once I test the psi maybe I can tune it in. It is a 2001 so I imagine it's adjustable but looks like a closed/fixed regulator.
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Yep, get a gauge on it and see where it is now. If this is a stock 2001 L18 with a return-type fuel rail it will have a factory adjustable regulator on the driver’s side of the fuel rail. In the middle of the regulator will be an inverted torx with a tamper proof tang in the middle. You can knock the tang off or use a tamper proof torx bit to adjust it. I like my 8.1’s running around 65-68 at idle. My K10 runs best at 68 psi and Burb about 65-66. The Workhorse RV 8.1s liked around 68 as well.

The bad news is if the regulator has been replaced it probably has a fixed one without an adjustment screw in the middle. If so, you’re screwed too. Even worse, is all of the replacement regulators from AC Delco, Standard, Huy Fong China’s Finest Auto Parts, etc. are all now sold without the ability to adjust them. The only thing to do is scour the salvage yards for a Vortec 1996 – 2003 5.0, 5.7, 7.4 or pre-2003 4.8, 5.3, 6.0 or 8.1 in hopes you find a factory adjustable one. Every adjustable regulator I find in the boneyards goes home with me in my pocket. I think some years of Buick 3.8’s used the same ones. I found some adjustable ones on SPA Turbo’s website for a BMW that looks like the ones we would use but not sure it would actually fit.

I’ve found the fuel pressure has to be below around 55 psi to really notice a huge loss in power. Anything above that usually performs okay but not as great as 62+. I think a lot of it also depends on the tune itself
 
Larry said:
Yep, get a gauge on it and see where it is now. If this is a stock 2001 L18 with a return-type fuel rail it will have a factory adjustable regulator on the driver’s side of the fuel rail. In the middle of the regulator will be an inverted torx with a tamper proof tang in the middle. You can knock the tang off or use a tamper proof torx bit to adjust it. I like my 8.1’s running around 65-68 at idle. My K10 runs best at 68 psi and Burb about 65-66. The Workhorse RV 8.1s liked around 68 as well.

The bad news is if the regulator has been replaced it probably has a fixed one without an adjustment screw in the middle. If so, you’re screwed too. Even worse, is all of the replacement regulators from AC Delco, Standard, Huy Fong China’s Finest Auto Parts, etc. are all now sold without the ability to adjust them. The only thing to do is scour the salvage yards for a Vortec 1996 – 2003 5.0, 5.7, 7.4 or pre-2003 4.8, 5.3, 6.0 or 8.1 in hopes you find a factory adjustable one. Every adjustable regulator I find in the boneyards goes home with me in my pocket. I think some years of Buick 3.8’s used the same ones. I found some adjustable ones on SPA Turbo’s website for a BMW that looks like the ones we would use but not sure it would actually fit.

I’ve found the fuel pressure has to be below around 55 psi to really notice a huge loss in power. Anything above that usually performs okay but not as great as 62+. I think a lot of it also depends on the tune itself
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OK I'll check in the am, as for the regulator I'll have to check. I'm runnin howell EFI tune and their harness. I'm still stumped about my fuel guage issue but almost feel it's tied into the running issue :dunno:
 
SpeedlabDan said:
Hey so I got my 8.1L running and aside from some issues with the fuel level and oil psi with the dakota dash it idles fine. Under power its gutless. It's my suspicion my fuel psi may be down and I plan on checking it tomorrow at the rail. If I can adjust the regulator, do you have a procedure? I'm using an ep381 pump so I feel the problem may be in pressure at the rail? For now I'm scratching my head but once I test the psi maybe I can tune it in. It is a 2001 so I imagine it's adjustable but looks like a closed/fixed regulator.
Click to expand...
You need to put a fuel pressure gauge on it and post up what you have when it's running. Normally an 8.1 needs 55-62 psi running. A fuel pressure regulator on a 2001 engine is adjustable. It's a small Allen head screw and little movements make a noticeable change. Watch your fuel pressure gauge as you make the adjustment. IIRC Larry tweaked his above spec slightly by a couple of pounds.
 
Larry: I've found a 2006 Suburban 2500 with only 35K miles on it. Obviously, it's the returnless setup. Looking at RockAuto, like you said, internal pressure regulators on all this stuff. Any idea how much pressure these returnless fuel modules are generally pushing? 50psi? What's the most power I can get out of this thing with a tune?

Would you just get an early fuel module and run a return line back from the regulator if I can find one?
 
buffy said:
Larry: I've found a 2006 Suburban 2500 with only 35K miles on it. Obviously, it's the returnless setup. Looking at RockAuto, like you said, internal pressure regulators on all this stuff. Any idea how much pressure these returnless fuel modules are generally pushing? 50psi? What's the most power I can get out of this thing with a tune?

Would you just get an early fuel module and run a return line back from the regulator if I can find one?
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Nah, even the returnless systems still run around 62 psi. The regulator is just built into the fuel module and can’t be adjusted. Personally, being a factory 8.1L in a near virgin Suburban I wouldn’t change the fuel system to return type.

Hard to guess on how much power one gets from a tune as no two tuners are the same and each tuner thinks they are better than every other tuner but I can tell ya, just having burst knock retard alone removed makes a huge seat of the pants difference as it did in my low mile virgin 2001 Pewterpuff Silverado.
 
Larry.......hoping you can provide some information on my build. I am swapping in a Vortec 454 7.4L. I had the harness and PCM reworked by Team208Motorsports. The transmission is the 4L80E. It is a 2WD tranny but I made the changes to 4WD. It has two speed sensors on the side of the tranny. Is this going to provide the signal needed to the PCM? Or is there some other type of part needed to get this engine to start and run?

When I had the 350 TBI, I used a speed sensor that hooked up to the NP241 to provide the signal to the speedometer, that sent the signal to the ECM. Wasn't sure if there is anything else since it was a 4L80E.

I am still a ways out on starting this engine, just wanting to know if there is anything I am missing once I am ready to get it rolling.
 
wheels87k5 said:
Larry.......hoping you can provide some information on my build. I am swapping in a Vortec 454 7.4L. I had the harness and PCM reworked by Team208Motorsports. The transmission is the 4L80E. It is a 2WD tranny but I made the changes to 4WD. It has two speed sensors on the side of the tranny. Is this going to provide the signal needed to the PCM? Or is there some other type of part needed to get this engine to start and run?

When I had the 350 TBI, I used a speed sensor that hooked up to the NP241 to provide the signal to the speedometer, that sent the signal to the ECM. Wasn't sure if there is anything else since it was a 4L80E.

I am still a ways out on starting this engine, just wanting to know if there is anything I am missing once I am ready to get it rolling.
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The second speed sensor (rearmost mounted) typically isn't used in 4wd applications since it would normally use the T-case output speed sensor as the input needed to the PCM for output speed.
 
Since my NP241 doesn't have the output speed sensor, it sounds like I would need to use both sensors from the 4L80E.

With the 350 TBI, the speed sensor that mounted to the np241 enabled the electronic autometer speedometer to work because they worked together with the sensor revs. It would then send the required signal to the ECM. I wasn't sure how the signal got to the L29 PCM except through the speed sensors on the 4L80E. I'm just trying to make sure I have everything necessary when it's time to start this thing and that it has the signal needed.
 
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wheels87k5 said:
Since my NP241 doesn't have the output speed sensor, it sounds like I would need to use both sensors from the 4L80E.

With the 350 TBI, the speed sensor that mounted to the np241 enabled the electronic autometer speedometer to work because they worked together with the sensor revs. It would then send the required signal to the ECM. I wasn't sure how the signal got to the L29 PCM except through the speed sensors on the 4L80E. I'm just trying to make sure I have everything necessary when it's time to start this thing and that it has the signal needed.
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Wouldn't that screw you up when/if in 4wdLow? The transmission output and transfercase output would be at different speeds - the ECM would be seeing the transmission speed signal but that would not match the actual speed.
 
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