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'78 K20 - RootBreaker from 1990 - nov 2025 8.1L not runnin

Kay86K5 said:
Sorry dude...but this is a ridiculous hodge-bodge of info here to try and follow...:confused:, but as long as you have all the info straight I guess that's all that matters.

But I did notice you had this written above: "Once you put the 8.1L engine in an old truck you will not be able to replace the crank sensor without removing the engine so do it now"...which is incorrect. I changed the crank sensor on my old motor while it was in the truck just fine. I was also able to change out the oil pressure sending unit (right next to the crank sensor) while the motor was in the truck too. Both were really not that hard to get in and out with the motor in the truck. Sure changing them while the motor is out is tons easier, but it can still be done just fine with the motor bolted in. This is just one of many misconceptions that I've read on the interwebs of people who have not actually tried to do things before, and just spill wrong information out everywhere.
Click to expand...


there, this is cleaner.. and fyi... I haven't done it yet so I cant vouch for the credibility of some things... thus the sensor replacement.. ill check it after truck is in but will replace while out. I also read that they starting making one with the connector on a 90 degree bend so will make sure that is what I get...



this is actually in the 8.1L resource thread but I want to pull it into here as I'm going to also update some pieces...

Ok adding my section to this. Was going to do my own but figured id stick it in here as it is not a high traction 5 million post thread. anyway.. I got through 3 pages to answer some of my questions. Got 13 more to go but gotta cook on the grill and family/eating time.be back later but thought I would share my notes I am taking.
correct me if I have some things wrong please..
this is jotted notes and all over the place. Tried keeping it somewhat organized and will clean it up later when things are confirmed...

8.1L parts...
* High Pressure fuel pump - EP381 Fuel pump
* fuel supply and return 2001 - 2003 The Workhorse part numbers for these lines are W0000539 Supply, W0000540 Return.
* regulator - built into 2001 - 2003 fuel rail
* Motor Mounts - Energy Suspension engine mounts - Energy Suspension 3.1116R
* Motor Cross Member - ORD GU32005
* Clutch stuff - 8.1L specific flywheel and pilot bearing (12582964 is the flywheel, 12563485 flywheel bolts & 12557583 pilot bearing). Supposeldy TBI 350 flywheel is internal balance thus should work and will find out
* EGR Block Plate
* Crank Sensor - can replace in truck against myth that you cant
* Accelerator pedal - can use gas pedal but 6.5 turbo diesel is a direct bolt in and 2 pins are different (pin A to J and J to A)
*mount pcm - 15764028 BRACKET - PCM W0007848 BRACKET - TCM 15003790 x2 BRACKET - TCM legs

Notes
* fuel lines - supply from motor 4-5 feet then put a filter in, click it in then take another hose and click it in and run to float assembly
* There is a small nub on the driver’s side of the engine that will need to be ground down just a tad so the engine mounts will bolt to the engine.
* Trans - SM465 - pull guide pins and will bolt to motor
* Clutch - use current sbc 350 pressure plate, clutch, etc? read need to drill holes for metric bolts for clutch?
* Exhaust - I don’t recommend using the 8.1L exhaust manifolds as they will hit the frame on an older truck. Any big block header or exhaust manifold (396, 402, 454, etc) will fit the 8.1L.
* Alternator - wire for charge goes where? gonna be bigger than my 60a I assume...
* Reading that low mount AC hits frame, but I do not need AC and have this style bracket - just remove and smaller belt.
Wiring
* Where to mount pcm - The Workhorse W0000393 ECM housing is the plastic piece the ECM snaps into.
I just used the TCM bracket as a cover per’se.
15764028 BRACKET - PCM
W0007848 BRACKET - TCM
15003790 x2 BRACKET - TCM legs
The 8.1L PCM is capable of managing dual fuel tanks. Get a tune from a cab and chassis 8.1L truck equipped with dual tanks, provide a fuel level signal from each tank and the PCM will operate your existing transfer pump to maintain the level between the two tanks. The PCM just controls a fuel pump relay for the transfer pump.
* My suggestion is to have them toggle off Torque Management, Toggle off EGR (and remove it from the engine), then add their “Hot” tune.
* Then when you get it running bump the fuel pressure up to about 67-68 psi and you’ll have a very strong runner that will start to find weaknesses elsewhere in your driveline .
Imma cheap-ass sum bit redneck... (actually father of 2 with sports, wife, bills, etc... ) so this is my budge 8.1L swap. I know others say you can get a motor for $1000 but expect to pay 2-3x that to install it... EFFFF DAT!!!!!

************************ Parts Purchased *****************************
2001 8.1L motor/harness/pcm/etc - facebook 8.1L group $1200
Motor Mounts: Energy Suspension 3.1116R - Amazon $55
ORD Big Block Engine Cross Member - ORD $223.50
2002 Silverado diesel gas pedal - car-parts.com $60
6AN Billet Fuel Filter - amazon - $10
AN6 stainless braided fuel line - ebay - $50
454 stock exhaust manifolds - friend - $45
EP381 fuel pump - amazon - $30
12563485 flywheel bolts - amazon - $10
2557583 pilot bearing - amazon - $20
Exhaust gaskets - fel-pro MS95840 - $13
Crank Sensor - duralast - SU1394 - $56
Rear main - Fel-Pro - 8540673 - $24​
Wires - Duralast lifetime - 4711 - $32
12559976 EGR Cover - thatgmpartsguy.com - $7 - $4 ship
12580673 EGR Cover gasket - thatgmpartsguy.com - $5

______________________________________________________________
Total.................................... $1844

************************ Parts Expected to Purchase *****************************
harness rework and "Hot Tune" - facebook guy - $300
true dual exhaust with stacks/flaps between rollbar - local - $300

Russell #644123 and #644113 to adapt 6an lines the the stock 8.1L rail
______________________________________________________________
Total.................................... $2444
 
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RootBreaker said:
there, this is cleaner.. and fyi... I haven't done it yet so I cant vouch for the credibility of some things... thus the sensor replacement.. ill check it after truck is in but will replace while out. I also read that they starting making one with the connector on a 90 degree bend so will make sure that is what I get...



this is actually in the 8.1L resource thread but I want to pull it into here as I'm going to also update some pieces...

Ok adding my section to this. Was going to do my own but figured id stick it in here as it is not a high traction 5 million post thread. anyway.. I got through 3 pages to answer some of my questions. Got 13 more to go but gotta cook on the grill and family/eating time.be back later but thought I would share my notes I am taking.
correct me if I have some things wrong please..
this is jotted notes and all over the place. Tried keeping it somewhat organized and will clean it up later when things are confirmed...

8.1L parts...
* High Pressure fuel pump - EP381 Fuel pump
* fuel supply and return 2001 - 2003 The Workhorse part numbers for these lines are W0000539 Supply, W0000540 Return.
* regulator - built into 2001 - 2003 fuel rail
* Motor Mounts - Energy Suspension engine mounts - Energy Suspension 3.1116R
* Motor Cross Member - ORD GU32005
* Clutch stuff - 8.1L specific flywheel and pilot bearing (12582964 is the flywheel, 12563485 flywheel bolts & 12557583 pilot bearing). Supposeldy TBI 350 flywheel is internal balance thus should work and will find out
* EGR Block Plate
* Crank Sensor - can replace in truck against myth that you cant
* Accelerator pedal - can use gas pedal but 6.5 turbo diesel is a direct bolt in and 2 pins are different (pin A to J and J to A)

Notes
* fuel lines - supply from motor 4-5 feet then put a filter in, click it in then take another hose and click it in and run to float assembly
* There is a small nub on the driver’s side of the engine that will need to be ground down just a tad so the engine mounts will bolt to the engine.
* Trans - SM465 - pull guide pins and will bolt to motor
* Clutch - use current sbc 350 pressure plate, clutch, etc? read need to drill holes for metric bolts for clutch?
* Exhaust - I don’t recommend using the 8.1L exhaust manifolds as they will hit the frame on an older truck. Any big block header or exhaust manifold (396, 402, 454, etc) will fit the 8.1L.
* Alternator - wire for charge goes where? gonna be bigger than my 60a I assume...
* Reading that low mount AC hits frame, but I do not need AC and have this style bracket - just remove and smaller belt.
Wiring
* Where to mount pcm - The Workhorse W0000393 ECM housing is the plastic piece the ECM snaps into.
I just used the TCM bracket as a cover per’se.
15764028 BRACKET - PCM
W0007848 BRACKET - TCM
15003790 x2 BRACKET - TCM legs
The 8.1L PCM is capable of managing dual fuel tanks. Get a tune from a cab and chassis 8.1L truck equipped with dual tanks, provide a fuel level signal from each tank and the PCM will operate your existing transfer pump to maintain the level between the two tanks. The PCM just controls a fuel pump relay for the transfer pump.
* My suggestion is to have them toggle off Torque Management, Toggle off EGR (and remove it from the engine), then add their “Hot” tune.
* Then when you get it running bump the fuel pressure up to about 67-68 psi and you’ll have a very strong runner that will start to find weaknesses elsewhere in your driveline .
Imma cheap-ass sum bit redneck... (actually father of 2 with sports, wife, bills, etc... ) so this is my budge 8.1L swap. I know others say you can get a motor for $1000 but expect to pay 2-3x that to install it... EFFFF DAT!!!!!

************************ Parts Purchased *****************************
2002 8.1L motor/harness/pcm/etc - facebook 8.1L group $1300 Still pulling motor and needs to ship
Motor Mounts: Energy Suspension 3.1116R - Amazon $55
ORD Big Block Engine Cross Member - ORD $223.50
2002 Silverado Diesel 2500 Accelerator Pedal with sensor - online junkyard $60
Click to expand...

That is much, much easier to follow now, haha.

On the crank sensors...any and all sensor you try and purchase now will all be the "90 degree" style you are referring too. The earlier years (IIRC 01-03) they had problems with the sensors going out with not that many miles on them. They finally redesigned the sensor to the "90 degree" style you are referring to and had much better luck with them. Therefore, it doesn't matter if you go to O'reilly's and try to buy a new sensor for a 2001 8.1, they all will be the "90 degree" style you are going for. See 1st pic below...old style that failed a lot is on the right (you can see the plug is turned sideways), new style is on the left (plug is more flat once it's bolted to the block).

I ended up using the same brackets Larry did for mounting my PCM (all the part numbers he listed in the swap resource thread). See the 2nd and 3rd pics below. I mounted it on the driver side wheel well right behind the washer fluid (I think Larry bolted his on the passenger side IIRC). Just drilled a couple holes there and bolted it up. I like that I got all the stuff larry said cause it made it a really nice place to mount my stand along fuse box and also the DBW pedal modual on the top bracket too (what larry referred to as W0007848 BRACKET - TCM)

You are correct that you can use your existing clutch pack that's in your truck currently for the 350. Then just get the 8.1 specific flywheel (they do have two or three little dowl pins sticking up on that flywheel for some reason...just grind them down flat), and like you mentioned above, you just need to drill out the 6 holes on your clutch pack so the metric bolts can fit them (literally...just drill them barely larger than what they are now is all you need), and that's it!

I did the DBW pedal that came out of the truck. Cut the arm off, beat it how I wanted, welded back together, then bolted it to the firewall (had to drill one hole in my firewall) and that was it. But as you said, you can use the 6.5 pedal and just change the two pin locations. I had the pedal so decided just to use it how I wanted instead of purchasing a different pedal.

Other than that, sounds like you are on the right track!

1.jpg

2.jpg

3.jpg
 
Kay86K5 said:
......Then just get the 8.1 specific flywheel .............
Click to expand...


I'm reading my flywheel will work as well... so will give it a try...


*******edited

found it..
post 27

I finally got a chance to pick up my flywheel for the 8.1 today. Seems I wasted my money
biggrin.gif


The stock 8.1 flywheel and a TBI 350 flywheel are the same with the exception of two roll pins for the 8.1 pressure plate. The ring gear, crank bolt pattern, center hole, pressure plate bolt pattern etc are all the same. The stock 8.1 pilot "bushing" (it's a sealed roller bearing) will also work with the 465.

I took some pics of the 8.1 flywheel with the TBI flywheel and clutch parts.

http://www.pirate4x4.com/forum/7643338-post27.html
 
Yeah, never had any experience with that so not sure if it really works with no problems. I swapped from a TH400 to a NV4500 at the same time I did the 8.1 swap, so since I had to get a flywheel anyways, I just got the 8.1 version. Hopefully it works
 
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8.1L bound!!!!!!!!!!

I just paid $800 for motor that is running ... 2001 with 145k miles... pcm, harness (got ripped at cab but got a guy to rework it) and pedal... $400 shipping... so still $1200!!!!! got to hear it run before he pulled it.. just been working on this deal since april
 
Kay86K5 said:
That is much, much easier to follow now, haha.

On the crank sensors...any and all sensor you try and purchase now will all be the "90 degree" style you are referring too. The earlier years (IIRC 01-03) they had problems with the sensors going out with not that many miles on them. They finally redesigned the sensor to the "90 degree" style you are referring to and had much better luck with them. Therefore, it doesn't matter if you go to O'reilly's and try to buy a new sensor for a 2001 8.1, they all will be the "90 degree" style you are going for. See 1st pic below...old style that failed a lot is on the right (you can see the plug is turned sideways), new style is on the left (plug is more flat once it's bolted to the block).

I ended up using the same brackets Larry did for mounting my PCM (all the part numbers he listed in the swap resource thread). See the 2nd and 3rd pics below. I mounted it on the driver side wheel well right behind the washer fluid (I think Larry bolted his on the passenger side IIRC). Just drilled a couple holes there and bolted it up. I like that I got all the stuff larry said cause it made it a really nice place to mount my stand along fuse box and also the DBW pedal modual on the top bracket too (what larry referred to as W0007848 BRACKET - TCM)

You are correct that you can use your existing clutch pack that's in your truck currently for the 350. Then just get the 8.1 specific flywheel (they do have two or three little dowl pins sticking up on that flywheel for some reason...just grind them down flat), and like you mentioned above, you just need to drill out the 6 holes on your clutch pack so the metric bolts can fit them (literally...just drill them barely larger than what they are now is all you need), and that's it!

I did the DBW pedal that came out of the truck. Cut the arm off, beat it how I wanted, welded back together, then bolted it to the firewall (had to drill one hole in my firewall) and that was it. But as you said, you can use the 6.5 pedal and just change the two pin locations. I had the pedal so decided just to use it how I wanted instead of purchasing a different pedal.

Other than that, sounds like you are on the right track!

View attachment 265496

View attachment 265497

View attachment 265498
Click to expand...
As for changing the sender in the back I'm glad I did min on the stand. There's no possibility I would have got the old one broke loose in a confined space. 197k worth of heat cycles had that sucker almost permanently bound. It took a long box wrench and some persuasion. I'm so glad.
 
SpeedlabDan said:
As for changing the sender in the back I'm glad I did min on the stand. There's no possibility I would have got the old one broke loose in a confined space. 197k worth of heat cycles had that sucker almost permanently bound. It took a long box wrench and some persuasion. I'm so glad.
Click to expand...


Ive been tossing that around. Others say u can swap it in the truck. Maybe unbolt it then bolt back so its loose?
 
RootBreaker said:
Ive been tossing that around. Others say u can swap it in the truck. Maybe unbolt it then bolt back so its loose?
Click to expand...
The way I looked at it :its old and fairly inexpensive so why not. That's why I was asking Larry about the sender for the factory dash and what sender was needed for that but I'm an all or nothing guy these days so it'll just take longer for me to finance this
 
Im waiting on one more package. Has gas pedal...2 computers not pcm and obd in cab plug side.

Ill be selling some of the stuff... gas pedal and i have no clue what 2 computers are for. Tpm.. transmission? Other dunno... and air conditioning as i dont have that

But will need to remove harness pcm and ship out. Got a guy gonna do a hot tune and rework/fix harness...

Then when that gets back to me ...truck comes apart...
 
RootBreaker said:
Im waiting on one more package. Has gas pedal...2 computers not pcm and obd in cab plug side.

Ill be selling some of the stuff... gas pedal and i have no clue what 2 computers are for. Tpm.. transmission? Other dunno... and air conditioning as i dont have that

But will need to remove harness pcm and ship out. Got a guy gonna do a hot tune and rework/fix harness...

Then when that gets back to me ...truck comes apart...
Click to expand...
Don't happen to have workhorse brackets for the Ac comp/at do you?
 
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