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L18 8.1L swap resource thread

My 8.1 swap has been completed now for about a month so I thought I'd post what I did for my oil cooler since most people bypass it.

Parts I used:
- 2x 72" 1/2NPT hydraulic lines from tractor supply

- 2x 1/2" 45 degree elbows from amazon (not happy with their quality, so no link).

- 4x 1/2" NPT swivels: https://www.surpluscenter.com/Hydra...el-Straight-1404-08-08-Adapter-9-1404-8-8.axd

- oil cooler with 1/2 NPT lines: https://www.summitracing.com/parts/der-13614

I removed the factory oil cooler fittings from the block and replaced them with NPT swivels. I also put swivels in the oil cooler, probably not necessary but makes life easier.
From there it was very simple, put the 45's on the hoses and hook them to the block:
KLZQ2Myh.jpg


On the front of the truck I just made a quick bracket to hold the oil cooler. Those aluminum bars are visible through the grille and driving me mad, I need to paint them. I think also technically it should be mounted on rubber grommets to avoid stressing the core, I'll likely do that at some point.
nNXEcoUh.jpg
 
chrisgt said:
My 8.1 swap has been completed now for about a month so I thought I'd post what I did for my oil cooler since most people bypass it.

Parts I used:
- 2x 72" 1/2NPT hydraulic lines from tractor supply

- 2x 1/2" 45 degree elbows from amazon (not happy with their quality, so no link).

- 4x 1/2" NPT swivels: https://www.surpluscenter.com/Hydra...el-Straight-1404-08-08-Adapter-9-1404-8-8.axd

- oil cooler with 1/2 NPT lines: https://www.summitracing.com/parts/der-13614

I removed the factory oil cooler fittings from the block and replaced them with NPT swivels. I also put swivels in the oil cooler, probably not necessary but makes life easier.
From there it was very simple, put the 45's on the hoses and hook them to the block:
KLZQ2Myh.jpg


On the front of the truck I just made a quick bracket to hold the oil cooler. Those aluminum bars are visible through the grille and driving me mad, I need to paint them. I think also technically it should be mounted on rubber grommets to avoid stressing the core, I'll likely do that at some point.
nNXEcoUh.jpg
Click to expand...
Looks good, and thank you for the technical details.
 
Does anyone know if I need a spacer between the flexplate and crankshaft, running a TH400 behind the 8.1?
 
Larry said:
- 2004-2010 Silverado, Sierra, G-Van and Workhorse L18’s moved to a returnless fuel system.
Click to expand...
Should this actually say Avalanche instead of G-Van as the last year for an 8.1 van was 02?
Or does the Avalanche retain the return style fuel system?
 
Capt Ron said:
Should this actually say Avalanche instead of G-Van as the last year for an 8.1 van was 02?
Or does the Avalanche retain the return style fuel system?
Click to expand...
Good catch! Yeah, since the G-van lost its 8.1 at the end of 2002 it shouldn't have been listed it there and Suburban/ Avalanche instead

Returnless vs. Return type is interesting as the Evaporate Emissions standards changed for 2004 in light vehicles where the feds didn't want warm fuel being returned to the fuel tank anymore because when the tank is warm with less than half tank, it puts out more fumes. Then when someone opens the gasshole to fill up they release all the pent up vapors out and unicorns and birds start dropping from the sky. So anything, somewhere around, 10,000 or 12,000 GVWR or lower had to have returnless for 2004. Higher GVWRs, like Medium Duty trucks and Workhorse, carried on for a while longer with Return type until as late as 2005 so an Avalanche would have gone returnless in 2004 along with everything else. It wasn't just 8.1s that went returnless for 2004, it was all gas engines at all manufacturers. Some manufacturers actually thought returnless was a good idea and changed to it much earlier than 04.
 
So i picked up this 02 with 96k on it but has a BAD sound . So i need to swap in another motor to get it done .

I have a 05 2500hd for the 8.1/allison combo . Or i have a short block from a 01-03 with 50k miles from a trusted seller to me .

Would you use the 05 and swap the stuff needed ? Or use the good top end from this truck on the 50k short block ?

Looking for best option for my new daily work truck . Thanks guys :pimp:

20231223_165545.jpg
 
sweetk30 said:
So i picked up this 02 with 96k on it but has a BAD sound . So i need to swap in another motor to get it done .

I have a 05 2500hd for the 8.1/allison combo . Or i have a short block from a 01-03 with 50k miles from a trusted seller to me .

Would you use the 05 and swap the stuff needed ? Or use the good top end from this truck on the 50k short block ?

Looking for best option for my new daily work truck . Thanks guys :pimp:

View attachment 465367
Click to expand...
If the HD truck is still a running truck, I would use the 50k engine.
Did you even try to diagnose your engine first?
Might be an easy fix.
96k is not much
 
I'm not saying it's not salvageable. But, it's had a couple of very bad days.
I'd short block it, just because it's a work truck and you need the reliability.
 
Anyone have the part number for the ball that mounts to the intake for the engine cover socket?

I searched the thread but did see anything.
 
GWeakland620 said:
Anyone have the part number for the ball that mounts to the intake for the engine cover socket?

I searched the thread but did see anything.
Click to expand...
Its in post #1 in the part number list :haha:

12567370 Engine Cover Ball Stud
12562957 Engine Cover Bracket (that the cover hinges on to at the other end)
 
What O2 sensor does the Howell harness use? I already searched a bunch of 8.1L build threads and it's not mentioned.
IMG_6452.jpg
 
skunked said:
What O2 sensor does the Howell harness use? I already searched a bunch of 8.1L build threads and it's not mentioned.
Click to expand...
I don't know which one that is. I built my own harness, I'm using the plugs that are kind of triangle shaped. I had to go through the alldata pig tail list to find mine.
 
BoondocK5 said:
I don't know which one that is. I built my own harness, I'm using the plugs that are kind of triangle shaped. I had to go through the alldata pig tail list to find mine.
Click to expand...

The 8.1’s are triangle shaped. I found some that look correct but I would rather have a part number and get it right without guessing.
 
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