88 Silverado LM7 swap, questions
Thread Starter
Joined: May 2006
Posts: 3,974
Likes: 2
From: Spring Hill, FL
88 Silverado LM7 swap, questions Well I originally was going to put a LT1 into my 88 Silverado. Found a 5.3 with trans, wire harness, most of the fuel and cooling system, all accessories, etc.. for dirt cheap. Picked it up and sold off some of the LT1 stuff.
Most of my questions are in wiring and fuel. I really have no idea what I should do for gauges, I thought about reusing the stock cluster, but it really is outdated looking.
Wiring wise I don't even know where to start. From the LM7 donor truck I have the whole wire harness, fuse block and everything. I thought about removing the old harness from the 88, but it looks like the engine wiring is also bundled in with the body harness? I also couldn't get the connector off the firewall on the driverside, is there some trick to it? Or will I not even need to pull that?
What are people doing for fuel in the OBS swaps? Is there some kind of drop in solution for the factory tank?
Any advice on getting the mechanical fan off? I have a LT1 fan setup still here, can I use it or is there a better electric fan option out there? (Better question, why the hell is GM still using mechanical fans on these truck motors? Come on man, join the modern age already!
)
I am going to mount it in the truck using the Dirty Dingo Double D aluminum mounts.
Well this is all I can think of for now off the top of my head. Mostly worried about the wiring. Thanks for any advice!
The truck:
The mess awaiting me when I get home from vacation:
Most of my questions are in wiring and fuel. I really have no idea what I should do for gauges, I thought about reusing the stock cluster, but it really is outdated looking.
Wiring wise I don't even know where to start. From the LM7 donor truck I have the whole wire harness, fuse block and everything. I thought about removing the old harness from the 88, but it looks like the engine wiring is also bundled in with the body harness? I also couldn't get the connector off the firewall on the driverside, is there some trick to it? Or will I not even need to pull that?
What are people doing for fuel in the OBS swaps? Is there some kind of drop in solution for the factory tank?
Any advice on getting the mechanical fan off? I have a LT1 fan setup still here, can I use it or is there a better electric fan option out there? (Better question, why the hell is GM still using mechanical fans on these truck motors? Come on man, join the modern age already!
)I am going to mount it in the truck using the Dirty Dingo Double D aluminum mounts.
Well this is all I can think of for now off the top of my head. Mostly worried about the wiring. Thanks for any advice!
The truck:
The mess awaiting me when I get home from vacation
: Last edited by camar0corey; Dec 31, 2011 at 04:22 PM.
Teching In
Joined: May 2009
Posts: 8
Likes: 0
From: Corpus Christi TX
I am going to be watching this... I have a 96 GMC Sierra that i want to do this swap to... It has a 305 and 4l60-E and i have the motor and going to use the trans since it was rebuilt 4 months ago... GL
Staging Lane
Joined: Jun 2011
Posts: 64
Likes: 0
From: Sioux Lookout, Ontario
For fuel, you'll just need to drop your tank and swap in a higher pressure pump. Should be a bolt in affair, replacing the TBI pump. Most use a walbro 255, but the choice is yours, needs to make at least 60 psi. Most use a corvette fuel filter/regulator to knock the pressure to the correct 58 psi the engine needs, and you'll have to run high pressure line all the way through.
Send the harness off to have it done. I used lsx harness. They were reasonable, and kept several grey hairs from forming. They also do computer editting.
Using you're gauges depends on what you have. The ls engines have spare ports for a temp sensor, hookup your oil pressure, and the ecm has an output for a tach.
Send the harness off to have it done. I used lsx harness. They were reasonable, and kept several grey hairs from forming. They also do computer editting.
Using you're gauges depends on what you have. The ls engines have spare ports for a temp sensor, hookup your oil pressure, and the ecm has an output for a tach.
We are going to be performing a swap in a 90 Chevy Truck that we use for shop use. Putting an 04 DBW LQ4 in with a 4l60e. Plans are to possibly make an adapter harness for the truck so you can easily weed out what you dont need on your 88. Might be a while though before it goes into production.
Regardless, there is a lot of wiring in the truck you can get rid of if you dont want it, if not, standalone would be my suggestion, but then again I am biased.
For fuel system, I am planning on dropping in a wahlbro 255 into the stock tank (this should be a direct bolt in). You can run the correct fuel regulator/filter if you are going to use returnless style fuel rails or use the stock lines with adapter fittings for a return style setup.
Regarding gages. Oil pressure and water temp can be wired independently to the engine harness as you will have to use the gage senders from the 88. As stated, Tach and Speedo output can come from the LS PCM, although output settings would have to be adjusted to read correctly.
Jon
PSI
Regardless, there is a lot of wiring in the truck you can get rid of if you dont want it, if not, standalone would be my suggestion, but then again I am biased.
For fuel system, I am planning on dropping in a wahlbro 255 into the stock tank (this should be a direct bolt in). You can run the correct fuel regulator/filter if you are going to use returnless style fuel rails or use the stock lines with adapter fittings for a return style setup.
Regarding gages. Oil pressure and water temp can be wired independently to the engine harness as you will have to use the gage senders from the 88. As stated, Tach and Speedo output can come from the LS PCM, although output settings would have to be adjusted to read correctly.
Jon
PSI
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Facebook/psiconversion
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'Dont Let EFI Pass You By!'
I'm currently doing a similar swap, 1988 C-1500 pickup with a 2003 5.3L, DBW, 4L60E and PCM from same year.
I will use the stock instrument cluster, I'm planning to make all gauges work.
Most of the stock wiring from the original engine will be deleted, only the wires for cluster signals will be used. Both harnesses will be integrated into one, the PCM will control as many systems as possible, including fans, fuel pump, starter, alt, MIL light, etc.
The stock engine harness is on the passenger side, no wires are needed there. On driver's side it has another connector for cluster, fuel pump, lights and some other wires you will need.
ABS and cruise control are the only systems I still have doubt. I have everything else figured out.
Engine, trans, radiator, fuel pump, fuel lines etc. are finished. I'm working on the electric stuff now so I'm a little ahead of you. If you need any assistance feel free to ask.
I will use the stock instrument cluster, I'm planning to make all gauges work.
Most of the stock wiring from the original engine will be deleted, only the wires for cluster signals will be used. Both harnesses will be integrated into one, the PCM will control as many systems as possible, including fans, fuel pump, starter, alt, MIL light, etc.
The stock engine harness is on the passenger side, no wires are needed there. On driver's side it has another connector for cluster, fuel pump, lights and some other wires you will need.
ABS and cruise control are the only systems I still have doubt. I have everything else figured out.
Engine, trans, radiator, fuel pump, fuel lines etc. are finished. I'm working on the electric stuff now so I'm a little ahead of you. If you need any assistance feel free to ask.
Thread Starter
Joined: May 2006
Posts: 3,974
Likes: 2
From: Spring Hill, FL
Hmm I'll look into this Lsx Harness place. Has anyone on here used Current Performance in FL for wiring? I'm local to them. Adapter harness sounds like a good idea also, at the rate I'm moving on this project it might be ready when I am.
Yeah I'm just torn on if I want to use the stock cluster or not. Its not horrible looking by any means I guess. I would like to retain cruise control also. The motor I have isn't DBW so maybe I have it easier then?
Def. plan to pull the bed to deal with the tank. I dropped it once before when it was empty and that was a big enough pain in the ***, now its completely full! I had just filled it up when it destroyed its 2nd 700r4 in less than two years. One of the reasons for this project, I hate TV cables. Also that 350 TBI has no *****.
Yeah I'm just torn on if I want to use the stock cluster or not. Its not horrible looking by any means I guess. I would like to retain cruise control also. The motor I have isn't DBW so maybe I have it easier then?
Def. plan to pull the bed to deal with the tank. I dropped it once before when it was empty and that was a big enough pain in the ***, now its completely full! I had just filled it up when it destroyed its 2nd 700r4 in less than two years. One of the reasons for this project, I hate TV cables. Also that 350 TBI has no *****.
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Well, today I was able to crank the engine. It didn't start because fuel tank is empty, but it looks good so far.
Crank signal is sent to starter by the PCM (but using stock '88 ignition switch and key), fuel pump primes and stops like it should.
Voltmeter and fuel gauges are working good. Oil pressure and coolant temp seem to be working but I need the engine to start to verify.
It is a lot easier than it seems. Once I checked the whole harness and deleted the whole passenger side, everything started to go smoothly.
This truck didn't come with cruise control from factory, so it's one thing less to worry about.
Crank signal is sent to starter by the PCM (but using stock '88 ignition switch and key), fuel pump primes and stops like it should.
Voltmeter and fuel gauges are working good. Oil pressure and coolant temp seem to be working but I need the engine to start to verify.
It is a lot easier than it seems. Once I checked the whole harness and deleted the whole passenger side, everything started to go smoothly.
This truck didn't come with cruise control from factory, so it's one thing less to worry about.
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Brett Foote
Staging Lane
Joined: Jun 2011
Posts: 64
Likes: 0
From: Sioux Lookout, Ontario
I used LSX harness about 3-4 months ago. Sent them a complete vehicle harness and pcm. Was done in less than a month, and cut down to simple 3 wire installation to make it run. Only issue I had was with PCM programming; running the LS with a manual trans, and he forgot to delete the automatic trans programming. Brought it up with him, and he was more than happy to fix it for me free of charge. Harness was all taped and labeled nicely. Will be using them again. Also seems to be the cheapest around.
Thread Starter
Joined: May 2006
Posts: 3,974
Likes: 2
From: Spring Hill, FL
Dothedew, what did it run you if you don't mind me asking?
So hit a weird snag today now that vacation time is over. Went to pull the motor mounts so I could clean things up and undercoat before I stab the motor in, they won't come off? It doesn't look possible to put a nut on the underside, I assume they would be like in a car and the k member would be threaded for the motor mount bolts? There is resistance, but no matter how many times I turn the bolts they don't seem to be going anywhere? Am I missing something?
Who has the best price on some new motor mounts? I can move these around freely in the clamshells and looks like the rivets have never been drilled out, kind of looks like stock 250k motor mounts from 1988.
So hit a weird snag today now that vacation time is over. Went to pull the motor mounts so I could clean things up and undercoat before I stab the motor in, they won't come off? It doesn't look possible to put a nut on the underside, I assume they would be like in a car and the k member would be threaded for the motor mount bolts? There is resistance, but no matter how many times I turn the bolts they don't seem to be going anywhere? Am I missing something?
Who has the best price on some new motor mounts? I can move these around freely in the clamshells and looks like the rivets have never been drilled out, kind of looks like stock 250k motor mounts from 1988.
http://67-72chevytrucks.com/vboard/s...d.php?t=377348
currentperformance did my wiring for my '82. give em a call! & as far as the mech fan, i had hell with mine. eventually put the belt back on, an took a 4 LB hammer & a 15" crescent wrench got it off
currentperformance did my wiring for my '82. give em a call! & as far as the mech fan, i had hell with mine. eventually put the belt back on, an took a 4 LB hammer & a 15" crescent wrench got it off
Thread Starter
Joined: May 2006
Posts: 3,974
Likes: 2
From: Spring Hill, FL
Not much of an update, but I guess I'm starting to move a little on it. Got the motor mounts out!
Ordered some Prothane mounts for it, I like them in my Camaro so I figured why not?
Might try to stab the motor/trans in this week.
Ordered some Prothane mounts for it, I like them in my Camaro so I figured why not?
Might try to stab the motor/trans in this week.
TECH Addict
Joined: Aug 2005
Posts: 2,305
Likes: 126
From: Monroe,NY
I will be doing a 5.3 in my 1992 chevy pickup in the beginning of April on my vacation.I will be watching this thread.When i bought my motor it came with a stand alone harness.All i have to hook up is power,tach, fuel pump and grounds.Plus i bought adapters to install temp and oil sensors to work with my original gauges.You still need to use the 5.3 temp sensor for the computer to work correctly.
Good Luck.
Good Luck.
Registered User
Joined: May 2016
Posts: 1
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Montecarlodrag.....
Did you take detailed notes when you completed this swap on ur 88? I am currently doing this swap but have a 2005 5.3 into a 88 chevy silverado. Anyhow, what you did is basically the same as I want to do... use existing wires to cluster and existing relays and etc... anything you have will help... thx. Wade
Did you take detailed notes when you completed this swap on ur 88? I am currently doing this swap but have a 2005 5.3 into a 88 chevy silverado. Anyhow, what you did is basically the same as I want to do... use existing wires to cluster and existing relays and etc... anything you have will help... thx. Wade