LS Swap: Introduction, newbie, planning...

[Davidf]

So, I just finished the rust repair, body and paint, and interior restoration (71, Cheyenne long). Suspension was rebuilt a few years ago. Now that all that is in great shape, my attention has turned to doing something about the tired old sbc 350 with factory air.

So, of course, what else to do but drop in an LS! I have been reading up on how I want to accomplish the task and recently found my donor vehicle. My neighbor is getting rid of his 2001 Tahoe (about 150k miles) and will sell me the entire vehicle for about $1k. So, LM7 has been sourced.

I think I will leave the engine stock for now and just get it installed and running. Of course, I will reseal the bottom end before installing. My truck has a 700R4 currently, but that will go in favor of the 2001 Tahoe trans (assuming 4L60E). Also, I will keep my in cab fuel tank.

So, any advice on engine mounts (want to keep factory stands, if possible) that will allow me to keep the LS a/c compressor, fuel system, etc. would be appreciated. I have done a lot of research and have ideas on all this, but hearing it again is never a bad idea. Also, I will use this thread to post progress...hopefully.

With that said, I probably won't start the project for a few weeks as I am still collecting data and don't have my neighbors vehicle yet...

Thanks in advance. Oh, I want this truck super reliable, able to pull a 4000 lb trailer all day long as far as I want to go, etc.

[mongocanfly]

easiest way to install LS engine is get a set of adapter plates... thatll alow you to use all thew sbc mounts..and puts the rear of the LS in the same location as the sbc
i used the ol ebay plates on mine...

[Gregski]

a couple tips if I may:

1. check all 12 (six per side) exhaust manifold bolts while the engine is out of the vehicle, they tend to break, and it's so much easier to get them out while the engine is out of the vehicle

2. check all 12 exhaust manifold bolts, lol now may be the time to replace the fugly EGR three hole flange stock manifolds with the cast Hooker two hole flange ones, the stock ones love to kiss the frame of the truck

3. remove the oil pan and please wash it out with Dawn dish soap so that you can eat Cheerios out of it, no sense on adding new oil to the sludge on the bottom of the old pan

4. check your water pump pulley and spin all pulleys, belt tensioner, idler, etc without the belt on and listen for wierd noises or any dragging, now's the time to change those if you like

5. remove the plastic intake manifold, don't be skierd, there is a mouse nest under there and you may want to evict them, clean that valley nice and good like

[Gregski]

6. pop off the valve covers and take a peak inside the valve train, do you see any sludgle? wiggle stuff around to see if anything is loose, good time to clean the valve covers and check for cracks

7. I would not go with aluminum motor mount plates, I would recommend steel and these from Dirty Dingo are fully adjustable

[Wgesnerjr]

Read Gregski's thread on PCM programming.

https://67-72chevytrucks.com/vboard/...d.php?t=792225

Bought HP Tuners and love it. Wish I would have done it his way rather than sending my PCM out to someone.

Also, read LT1Swap.com for wiring info.

https://www.lt1swap.com/

Even if you plan on using a premade harness, it's good reading to know for your swap.

[Davidf]

Awesome, all great info. So, more of my initial thoughts:
1. I will definitely remove the oil pan and check/clean. New water pump, new knock sensors and valley cover, new rear main seal and cover gasket. New trans input shaft seal.
2. Steam line into heater hose nipple on my new aluminum radiator. The nipple has internal threads to accept a barbed fitting.
3. I will do my own wiring harness following LT1Swap.com. I know about HP Tuners and debating on the $400 up front cost, or just getting LT1Swap to remove VATS and emissions for $75. If I ever install a BTR Torque cam later down the road then I will probably pull the trigger on HP Tuners.
4. My thought was to buy Trailblazer SS exhaust manifolds. Are the Hooker better or cheaper? Definitely, the EGR stuff is going away.

Question:
1. How do you hook up throttle cable? Are there custom cables made for this purpose that are the correct length with the correct ends? I have not studied this part at all.
2. Will my stock perches and engine mounts work with the adapter plates (whether DD or Speed Engineering)?
3. What should I expect as far as interference with the LS stock a/c compressor.

Great advice on the exhaust bolts. Why not studs with copper nuts?

Then, there is the fuel system...I have pretty much decided on an external pump setup. Will use the vent line in the sender for the return and extend it to the bottom of the tank. I am also thinking I will fab up a fuel bucket that clamps to the pickup tube and will fit through the sender hole. The return will return into the bucket. My hope is that this will solve fuel starvation with low fuel levels. The question will be how large a hole to drill into the bottom of the bucket so it fills fast enough but does not drain too fast. My guess is to start with a 3/16" hole.

[Gregski]

David sounds like you are no stranger to turning wrenches in which case I have to stand my ground and say a hard no to an external fuel pump. Internal pumps use the gas to cool themselves and don't have to work as hard, as a pump is more of a push than a pull, they are better at pushing fluid than sucking it out of the tank.

As far as the motor mounts, I too have a '71 however it's the only truck out of three that I haven't done an LS Swap on, (have something even more radical in store for that one) however when it comes to the motor mounts check to see if your stock clam shells are the truck type or the car type, no reason for them to be the car type but it being 50 years old who knows. The car type on the left in the pic below have a raised pattern on them (bad, won't mount flush) the truck ones are indented (good) will mount flush with the LS plates, some folks grind the car shells flush, I would just get the correct truck kind if you don't have them already, hope that makes sense

I recommend the Dirty Dingo plates just for that, if you want to keep your AC, you have a better chance if you use them.

The 2001 is a good year for a donor engine because they were still cable drive (vs drive by wire) throttles, this makes for an easy swap, the stock cable should work, you can just use lead fishing line weights to shorten it a tad at the peddle inside the cab, you can find the write up on my Restoring Rusty thread.

[Davidf]

So, if no external pump then who has had success with an internal pump in stock tank location without welding in a sump? I agree that in tank is best. But, noise is a potential issue. I am sure I could cobble something together.

[ls1nova71]

An external pump is never my first choice, but in a 67'72 Chevy truck, it can be done with great success because you can get the pump lower than the tank, not usually possible with a frame mounted tank. That said, you won't want to have it try and suck fuel up and out of the tank, even though a siphoning effect it should work, it doesn't always work well. You really need to have the fuel gravity feed into the tank as fast as the pump can push it, so ideally it needs to come out of the bottom of the tank. Thats what I do when using the factory tank and my truck has run flawlessly for the last 52k miles.

Putting the pump in the factory tank will drive you nuts unless you are either deaf, or always drive with the stereo turned up to 11 all the time!

This is my build on my driver truck, has a lot of the same things you are asking about, throttle cable, factory A/C might be worth a look. https://ls1tech.com/forums/conversio...71-c-10-a.html

[Davidf]

Originally Posted by ls1nova71

An external pump is never my first choice, but in a 67'72 Chevy truck, it can be done with great success because you can get the pump lower than the tank, not usually possible with a frame mounted tank. That said, you won't want to have it try and suck fuel up and out of the tank, even though a siphoning effect it should work, it doesn't always work well. You really need to have the fuel gravity feed into the tank as fast as the pump can push it, so ideally it needs to come out of the bottom of the tank. Thats what I do when using the factory tank and my truck has run flawlessly for the last 52k miles.

Putting the pump in the factory tank will drive you nuts unless you are either deaf, or always drive with the stereo turned up to 11 all the time!

This is my build on my driver truck, has a lot of the same things you are asking about, throttle cable, factory A/C might be worth a look. https://ls1tech.com/forums/conversio...71-c-10-a.html

Yes, I have seen your build post...good stuff! I applaud you for your approach and creativity. I tend to do the same at times. I think I will re-read your post and try to dig my out of the rabbit hole all the research is making me go down. I need to keep saying to myself "keep it simple..."

[notsolo]

On the manifold bolts, doesn’t take much to break them. I used a map gas torch heated up each bolt 20 seconds then carefully worked them out. Broke 2 before, but got both of them out.

[mongocanfly]

ive had a external pump on mine for a lot of yrs now...never had a issue with it..
if you use your tank vent for a return line youll still need to vent the tank somehow
the ebay adapter plates i used are steel ..not aluminum..they had options for mounting..i choose stock location...never used the dd but they should work fine...
not sure on the stock ac comp location.. would not fit on mine..it would require a frame notch..
for throttle cable, the one on my truck wouldnt work, so i pulled one at the junkyard from a 01 truck...had to reshape the firewall hole , but it works fine

[clay68c10]

I used the hooker black heart mount setup. Nicely designed and you use off the shelf F-body mounts.

[Davidf]

Ok, I agree. I have decided to go the Hooker Blackheart route. Some say the truck oil pan will clear and can keep the low mount a/c compressor. I’ll start with mounts and crossmember and go from there.

I also want to ditch the two piece driveshaft in favor of one piece. I just cannot seem to find a carrier bearing that lasts any appreciable length of time.

Neighbor took delivery of his new Tahoe, so I get the 2001 Tahoe this weekend....

A few planning decisions/updates:
1. Will do the wiring harness myself and send ECM to LT1swap.com
2. Plan on using and connecting cruise control from donor.
3. Leaning toward blackheart exhaust, but this may change.
4. Will use all my stock gauges so will use the Dakota Digital speedometer drive.
5. Will upgrade a/c to fixed orifice tube, so will use the donor a/c compressor an utilized "ac request" input signal and compressor control output from ECM. Will control condenser fans from relay so always on when ac on.
6. May try to implement condenser fans turn on via fan2 from ECM based on engine temp needs
7. Will keep mechanical fan.
8. Keeping stock in cab fuel tank.
9. External fuel pump.
10. One piece driveshaft
11. Keep donor air filter box...move battery to left side.
12. Mount ECM under hood.
13. Use aftermarket fuse/relay box to accommodate: all added fuses, fuel pump relay, main power relay, headlight relays, a/c compressor relay, and fan relays.
14. Still planning on resealing the bottom of the LS engine. Will wait on valley cover, knock sensors, and water pump.
15. Drill water pump for steam line and water temp sending unit for stock gauges (in lieu of right side cylinder head in case of Dakota Digital gauges in future).

Wish list:
1. Utilize low oil level switch to activate idiot light in fuel gauge (regardless, will keep the oil level circuit when cleaning up LS harness).
2. Dakota Digital gauges: So, will keep a few circuits in LS harness (oil pressure for example).
3. Tow/haul feature: Will keep wire/pin 71 when cleaning up harness. Add momentary button somewhere under bottom edge of dash or maybe in glove box light hole.

Anybody have an other ideas on what I should plan for, add, or just thoughts?

[gmc684x4]

Did you read the stickies for ls swaps there is lots of info in them as well

[ls1nova71]

Originally Posted by Davidf

1. Utilize low oil level switch to activate idiot light in fuel gauge (regardless, will keep the oil level circuit when cleaning up LS harness).

Your plan sounds an awful lot like my truck! LOL! On a side note, the Nova I did 20+ years ago, I kept the low oil light wiring and added another light to the dash, so that it has a low oil pressure and low oil light, and in all the years of driving it, it's never come on. That is for non car people who don't know how to open the hood, because it only comes on when you get to around 2 quarts or so of oil left in the pan, not something I would ever think anyone who does a swap would let happen. But, it doesn't hurt anything to add it and isn't hard at all, so might as well add it if it you want to.

Are you using the factory A/C or going aftermarket? If using the factory system, you can use both the high and low pressure sensors from the Tahoe and it will work like stock.

[Davidf]

Well, I cannot argue about your logic on the low level switch. But it can be of use if you have a catastrophic oil leak and get a bit of a a warning before you loose pressure. I will probably just keep the circuit and connector in the harness for possible future use.

As for the a/c, my truck has factory air. And I will keep all the interior components. But, I want to use the donor compressor, switch from R12 to R134a. I also want to switch from POA/TXV to accumulator/Fixed orifice tube (which will require a new evaporator). So, makes sense to keep high and low switches from donor is what you are saying. The way I understand it to work is that I will wire my existing compressor wire to the a/c request line on ECM (I think this signal goes through the high pressure switch). ECM compressor control will energize relay to activate compressor. And ECM low pressure cycling switch input will go through low side switch to ground. Easy peezy.

This is fun, learning a lot so far

[ls1nova71]

Sounds like you've got it figured out. What I did was use an evaporator out of a square body to get rid of the POA valve. Also used the low pressure sensor out of one too because most of them are adjustable, so you can fine tune the system a bit. The newer switches are all fixed.

[Davidf]

Originally Posted by ls1nova71

Sounds like you've got it figured out. What I did was use an evaporator out of a square body to get rid of the POA valve. Also used the low pressure sensor out of one too because most of them are adjustable, so you can fine tune the system a bit. The newer switches are all fixed.

Yes, 87 evap should fit existing housing. But, didn’t you use a more modern evap out of a late model truck and modified the housing to make it fit?

[ls1nova71]

Originally Posted by Davidf

Yes, 87 evap should fit existing housing. But, didn’t you you use a more modern evap out of a late model truck and modified the housing to make it fit?

Yes, I did that on my blue truck, but that was several trucks ago. LOL! I only did it once and wasn't really worth the effort since the square body stuff works. The evaporator is a bit smaller than the 67-72 one though, so you need to fill in about a 3/4" gap so the air doesn't just blow around it.

[TrybalRage]

Originally Posted by Davidf

Ok, I agree. I have decided to go the Hooker Blackheart route. Some say the truck oil pan will clear and can keep the low mount a/c compressor. I’ll start with mounts and crossmember and go from there.

I also want to ditch the two piece driveshaft in favor of one piece. I just cannot seem to find a carrier bearing that lasts any appreciable length of time.

Neighbor took delivery of his new Tahoe, so I get the 2001 Tahoe this weekend....

A few planning decisions/updates:
1. Will do the wiring harness myself and send ECM to LT1swap.com
2. Plan on using and connecting cruise control from donor.
3. Leaning toward blackheart exhaust, but this may change.
4. Will use all my stock gauges so will use the Dakota Digital speedometer drive.
5. Will upgrade a/c to fixed orifice tube, so will use the donor a/c compressor an utilized "ac request" input signal and compressor control output from ECM. Will control condenser fans from relay so always on when ac on.
6. May try to implement condenser fans turn on via fan2 from ECM based on engine temp needs
7. Will keep mechanical fan.
8. Keeping stock in cab fuel tank.
9. External fuel pump.
10. One piece driveshaft
11. Keep donor air filter box...move battery to left side.
12. Mount ECM under hood.
13. Use aftermarket fuse/relay box to accommodate: all added fuses, fuel pump relay, main power relay, headlight relays, a/c compressor relay, and fan relays.
14. Still planning on resealing the bottom of the LS engine. Will wait on valley cover, knock sensors, and water pump.
15. Drill water pump for steam line and water temp sending unit for stock gauges (in lieu of right side cylinder head in case of Dakota Digital gauges in future).

Wish list:
1. Utilize low oil level switch to activate idiot light in fuel gauge (regardless, will keep the oil level circuit when cleaning up LS harness).
2. Dakota Digital gauges: So, will keep a few circuits in LS harness (oil pressure for example).
3. Tow/haul feature: Will keep wire/pin 71 when cleaning up harness. Add momentary button somewhere under bottom edge of dash or maybe in glove box light hole.

Anybody have an other ideas on what I should plan for, add, or just thoughts?

I used summit racing manifolds on mine, great fit, seems like great quality. Cheaper than Hooker.

15. Not sure of your logic here, you can put in a 3 wire sensor from a 98 Camaro and have both temp inputs for the PCM and for the gauge.

[Davidf]

Originally Posted by TrybalRage

I used summit racing manifolds on mine, great fit, seems like great quality. Cheaper than Hooker.

15. Not sure of your logic here, you can put in a 3 wire sensor from a 98 Camaro and have both temp inputs for the PCM and for the gauge.

I like your thinking. Will the three wire sensor send the right right signal to my 71 gauge so it reads correctly?

I got the engine out of the ‘01 Tahoe. Next is clean up and inspection. I’m a little worried that the cylinder heads are cracked and letting coolant escape into the crankcase. PO mentioned mystery coolant lose and water pump looks newish...thinking water pump was attempted repair. No sign of radiator leak. Will know when I pull valve covers. Photos soon

[TrybalRage]

Originally Posted by Davidf

I like your thinking. Will the three wire sensor send the right right signal to my 71 gauge so it reads correctly?

I'm not sure on a 71. You'd have to look up the resistance ratings for the sensor and what your year truck would use. From what I understand thought, GM was pretty consistent with things like that for many years.

[Davidf]

Originally Posted by TrybalRage

I'm not sure on a 71. You'd have to look up the resistance ratings for the sensor and what your year truck would use. From what I understand thought, GM was pretty consistent with things like that for many years.

Yes, GM eventually got consistent, but I believe it happened well after 71.

[Davidf]

Yep, left head is cracked...baby poo on underside of valve cover. Right side is just oil and 185k mile crude. I think I will replace both heads with stock 862 or 709's. And, since the lifters ticked a few seconds on cold start, I will replace all lifters while the heads are off. At least the knock sensors and water pump are new(ish).

Going to stop short of a full rebuild...unless

And, man was that engine dirty!