I do think I'm goin for a fresh harness strait from the jump though but I'm using the factory cluster for now so I gotta figure out the oil psi sensor since it can't be accessed once in the truck.
CK5
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L18 8.1L swap resource thread
- Thread starter Larry
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I knew cam sensor cant be got to. Didnt know oil as well. Ive got a old school mechanical gauge so will need to do same. I also thought of saying screw it and put a tablet in my dash with torque pro and do up my own
Lol google pic not in english
cluster
That's an idea. It's the crank sensor but the oil psi sender is next to it above the bell
I read about 11 pages so far... side question... power steering. So return line is a return line but what do you do to connect high pressure side? 8.1L is metric fitting and 78 c20 pump standard size. Threads are different right?
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Wow, you guys have been tossing more balls at me than I could swing at lately.
A couple things…
As far as running the cluster gauges (assuming you guys are running square bodies), there is no reason to overthink the gauges and no reason to buy needless aftermarket BS like Dakota Digital (unless you want too). If you think about it, the gauges don’t know what engine they are reading nor do they care. All you need to do is use the trucks original circuits for the oil pressure, temp and volt meter (and Air Conditioning for that matter) and run them straight to the new engine. Those circuits are in the chassis harness that come out of the driver’s side of the firewall at the block (Except for A/C, that comes from the A/C box area).
- Temp Gauge: use a TS6469 - Temp Sending unit (Napa part number) as I mentioned on the last page and thread that into the driver’s cylinder head. There is a pipe plug in the head. Remove it and install this old BBC temp sending unit in there then plug your old existing temp gauge circuit to it
- Oil Pressure: Same here… use the wire that used to go to the old engines oil pressure gauge and either use an adapter to thread your old oil pressure gauge into the 8.1L Block, use an adapter to install a tube for a manual gauge or get the early 8.1L D1819A - Oil Sending Unit (AC Delco) and PT2326 - Oil Sending Unit Connector (AC Delco) and splice that onto the trucks original oil pressure gauge circuit
- Voltmeter: I like to run CS-144 alternators from a 96-00 L31/L29 as they are not computer controlled and can be had in amperages as high as 140 amps (I wouldn’t recommend the DS alternators that came on 8.1Ls). These CS alternators are inexpensive to buy new or reman as well. Just run the trucks original alternator wire (brown wire I believe) to the L terminal. Most stand alone harnesses will want an alternator feed as well so you will need to splice the engine harness to the same brown wire that goes to the L terminal.
- Starter: Again, use the circuits that were in the truck from the original engine. The 0411 ECM has the ability to run the starter motor but I wouldn’t recommend that. Run the starter just like it was on the old engine
- A/C: Same here. Keep the original A/C circuits and just change the end connector to match the new compressor if running A/C
If your trucks had Feedback carburetors or TBI, the wiring that goes through the big round hole in the firewall towards the middle of the passenger’s side can all be removed. The main circuits you will need all come from the driver’s side pass through connector.
The picture below gives you an idea of how much BS can be cut out of a feedback carburetor or TBI harness to keep only what you need. Luckily, on my Suburban swap I had an extra 1989 Suburban harness to chop up and still keep my OEM harness to sell with the TBI 5.7L that came out. This is a comparo between a stock TBI harness and a reworked/pruned harness. Word of advise, spend some money on a good factory GM wiring diagram for the year of your truck. Makes harness clean up so much easier knowing what you can safely cut out
After relooming
A couple things…
As far as running the cluster gauges (assuming you guys are running square bodies), there is no reason to overthink the gauges and no reason to buy needless aftermarket BS like Dakota Digital (unless you want too). If you think about it, the gauges don’t know what engine they are reading nor do they care. All you need to do is use the trucks original circuits for the oil pressure, temp and volt meter (and Air Conditioning for that matter) and run them straight to the new engine. Those circuits are in the chassis harness that come out of the driver’s side of the firewall at the block (Except for A/C, that comes from the A/C box area).
- Temp Gauge: use a TS6469 - Temp Sending unit (Napa part number) as I mentioned on the last page and thread that into the driver’s cylinder head. There is a pipe plug in the head. Remove it and install this old BBC temp sending unit in there then plug your old existing temp gauge circuit to it
- Oil Pressure: Same here… use the wire that used to go to the old engines oil pressure gauge and either use an adapter to thread your old oil pressure gauge into the 8.1L Block, use an adapter to install a tube for a manual gauge or get the early 8.1L D1819A - Oil Sending Unit (AC Delco) and PT2326 - Oil Sending Unit Connector (AC Delco) and splice that onto the trucks original oil pressure gauge circuit
- Voltmeter: I like to run CS-144 alternators from a 96-00 L31/L29 as they are not computer controlled and can be had in amperages as high as 140 amps (I wouldn’t recommend the DS alternators that came on 8.1Ls). These CS alternators are inexpensive to buy new or reman as well. Just run the trucks original alternator wire (brown wire I believe) to the L terminal. Most stand alone harnesses will want an alternator feed as well so you will need to splice the engine harness to the same brown wire that goes to the L terminal.
- Starter: Again, use the circuits that were in the truck from the original engine. The 0411 ECM has the ability to run the starter motor but I wouldn’t recommend that. Run the starter just like it was on the old engine
- A/C: Same here. Keep the original A/C circuits and just change the end connector to match the new compressor if running A/C
If your trucks had Feedback carburetors or TBI, the wiring that goes through the big round hole in the firewall towards the middle of the passenger’s side can all be removed. The main circuits you will need all come from the driver’s side pass through connector.
The picture below gives you an idea of how much BS can be cut out of a feedback carburetor or TBI harness to keep only what you need. Luckily, on my Suburban swap I had an extra 1989 Suburban harness to chop up and still keep my OEM harness to sell with the TBI 5.7L that came out. This is a comparo between a stock TBI harness and a reworked/pruned harness. Word of advise, spend some money on a good factory GM wiring diagram for the year of your truck. Makes harness clean up so much easier knowing what you can safely cut out
After relooming
Well, that is a decision you’ll need to make. Personally, I would first test fit the 78 C20 power steering pump to see if the reservoir will clear the 8.1L bracket. If so, just use it! Saginaw pump mounting has not changed in eons and will bolt on providing the reservoir clears the bracketry. The new serpentine pully will fit the old pump with no problem. Unfortunately, on my K10 I have a metric pump but standard thread gear box and hydroboost which means I had to custom make a high pressure hose. No biggie but could be a big issue if that hose blows while out on the annual desert trip where I can’t just walk into a dime store parts store for a new hose. In hind sight, I should have either found an older pump to work on the 8.1L to keep all connections SAE or updated the hydrobooster and gearbox to metric. I will need to deal with that one day. On the other hand, my Burb is all metric in all spots due to it being a 1989 (metric started in 1983/4 I believe).
^^^ Was wondering if you were sleeping or what!!!! HAH
and wow. I have always wondered about the wiring. I get it, cleaner, simpler and no big deal but to me it was like.. well if it works and all wires have a place, I don't care... just keep oem harness of 8.1L and don't remove anything. I see in your pic there is a HUGE difference.
With that I am planning on keeping all wires, etc.. and run it like that and get running without a tune for a bit. then endeavor on how to do a tune myself. I don't want to pay someone to tune, then in the future want something done and need another tune. id rather fork the cash out up front if it isn't too much and learn....
and wow. I have always wondered about the wiring. I get it, cleaner, simpler and no big deal but to me it was like.. well if it works and all wires have a place, I don't care... just keep oem harness of 8.1L and don't remove anything. I see in your pic there is a HUGE difference.
With that I am planning on keeping all wires, etc.. and run it like that and get running without a tune for a bit. then endeavor on how to do a tune myself. I don't want to pay someone to tune, then in the future want something done and need another tune. id rather fork the cash out up front if it isn't too much and learn....
Off topic from wiring, Larry, have you noticed on your Burban 8.1 that has headers, as compared to your K10 with manifolds, that your headers allow more valvetrain noise to be heard? Just curious is all
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Can’t say I’ve noticed any more valve train noises but I sure hear more flames going through the pipes with the headers. I also wouldn’t say I would jump through my own azzhole ever again to have headers again either. Headers aren't worth the expense and hassle in my opinion unless you are trying hard to squeeze every poney out of the engine as possible. The Burb doesn't have near the low end grunt the K10 has with manifolds but the K10 doesn't have the top end the Burb has. All in what you want out of it I guess.
FYI...all my factory gauges are now working on the 8.1 using Larry's part number he's listed above. I was able to change the oil pressure sending unit to the one Larry suggested with the motor in the truck. It was a little annoying to get the old out and the new unit it, but it wasn't horrible. Only took me about 15 min. to get it swapped out. And luckily, the plug on my driver side head came out with no trouble whatsoever (I have heard a lot of people say they couldn't get the plug out and had to drill it out), so I was able to install the temp sending unit easily. Thanks again Larry for the guidance...this thread is worth it's weight in gold for anyone wanting to swap, and learn more about these motors!
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Cool! Ya, I've never had an issue getting the pipe plugs out of any BBC in my life but I have had issues getting oil galley plugs out of some old 454s and 396's that needed to be drilled. Total PITA!
what if you have a manual oil gauge? ive got that oil line vs an electrical line...
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Dude, I already answered that a while ago. Remove the oil sending unit, get an adapter and screw your existing oil line to it. Simple... nothing unique here because it is an 8.1
Hmm aight i was just confirming. I figured no reason why i cant run all my sendors..just need metric to standard adapters
yeah found it... thx... sorry I missed it.. I got through the whole thread when I did my big "notes" post...
I was coming here to ask a question but got caught up in the rabbit hole deal.. hah...
well ended up on a thread that @Larry replied too and while I am glad it has good input.. not what I wanted to hear.. LOL...
So the guy hasn't pulled the 8.1L for me yet. He has been working on getting it out carefully so I have everything in tact. He just got 2 more 8.1L trucks.
From what I have read and what larry has said... 2001-2003 are return line based fuel rails and when you look at the motor specs... all 3 put out the same power.
now my delema...
Motor/Harness/PCM/gas pedal/everything....
I am getting a 2001 8.1L with 145k miles - $1000 + $300 shipping = $1300 shipped - leaves me with $1000 for parts for swap...
He offered me a 2002 8.1L with 105k miles - $1750!!!! + $300 shipping = $2050 shipped - leaves me with $300 for parts for swap...
I still need to get the fuel pump, new sending unit so I can solder on an6 fittings, fuel lines (supply/return), 454 manifolds, odds/ends
now I was going to buy my own tuner... don't want to get into that debate now.. but still.. I could just not do that and get the 2002...
so @Larry says his 2002 runs like a different animal. this guy is telling me that this 8.1L is the best sounding one he has had... of course he wants more money so I figured he was just saying that.. but Larry is saying it too on his....
what to do ... what to do....
well ended up on a thread that @Larry replied too and while I am glad it has good input.. not what I wanted to hear.. LOL...
So the guy hasn't pulled the 8.1L for me yet. He has been working on getting it out carefully so I have everything in tact. He just got 2 more 8.1L trucks.
From what I have read and what larry has said... 2001-2003 are return line based fuel rails and when you look at the motor specs... all 3 put out the same power.
now my delema...
Motor/Harness/PCM/gas pedal/everything....
I am getting a 2001 8.1L with 145k miles - $1000 + $300 shipping = $1300 shipped - leaves me with $1000 for parts for swap...
He offered me a 2002 8.1L with 105k miles - $1750!!!! + $300 shipping = $2050 shipped - leaves me with $300 for parts for swap...
I still need to get the fuel pump, new sending unit so I can solder on an6 fittings, fuel lines (supply/return), 454 manifolds, odds/ends
now I was going to buy my own tuner... don't want to get into that debate now.. but still.. I could just not do that and get the 2002...
so @Larry says his 2002 runs like a different animal. this guy is telling me that this 8.1L is the best sounding one he has had... of course he wants more money so I figured he was just saying that.. but Larry is saying it too on his....
what to do ... what to do....
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I didn't think there was much difference between the 01 and O2... Thought it was just Egr and fuel return stuff
right and the guy selling it says it sounds strong, sounds like a great runner... of course he is selling it.. salesman tools... BUT reading what larry said.. made me question the validity...
in all honesty.. I cant afford it. budget is tight now so if I did get it, it would set me back.. guess ill stick with my original plan
Stick with the 2001
You'll still get plenty of power
Dude, absolutely no difference between 2001 and 2002 motors. The reason why Larry said his motor runs so much better in his K10 is because of the tune he had done to the ECM. His 2001 Silverado is completely stock. So he was just giving comparison between a stock ECM in his 01 vs his custom tune ECM in his 2002 swapped motor. Both 2001 and 2002 have the return style fuel rail, so no difference there. And honestly, when looking at two different 8.1's that are both under 150K...I would go with the cheaper one for sure....40k less miles would not be worth almost a grand more out of pocket to me. Go with the cheaper one cause you are going to find out real quick that the rest of the parts you need for the swap is what nickels and dimes you to death.
