Gen 3/4 LS vs Gen V LT Differences

[HYPR]

Geez, I am learning a lot. More information that I never knew and at this point wish I had known before. OK, After speaking with ICT and now watching this YOUTUBE from LOJ Conversions. https://www.youtube.com/watch?v=280o3rhAZHkI have learned that almost nothing available on the LS is automatically useable for an LT installation. Good to know now rather than later. One thing I was told from the start is to swap out the LT water pump for the LS style...Well not so fast, see there is a reason this is not necessarily not a domino effect change. See the LS style interferes with the VVT drive actuator. Next are something really simple, Exhaust manifolds/Headers...yep not interchangeable as the exhaust ports are offset .625" on the LT and they are even different right to left unlike the LS.
OK, now for a real head banger. According to ICT the mounting bolt pattern on the AC pump housing is different on the LS and LT. In addition Holley make a low mount AC bracket for the GEN V LT but only for the Dry Sump 6.3 not the 5.3. My desire was for the purpose of keeping everything clean was to leave the AC compressor mounted low so as to not make it impossible to deal with the PS pump Reservoir or necessitate mounting a remote Reservoir. I may have no choice unless someone can dispute what ICT is saying about the lower AC mounting points being different on the LS vs LT. If they are different I may just have my son cut up some that fit the LT on his CNC Plasma table. We will see.
So...Question is can dispute or confirm what ICT is saying about the lower AC mounting points being different on the LS vs LT?
Sorry for the double posting in two different forums DUH!

[barraza]

http://67-72chevytrucks.com/vboard/s...d.php?t=819493

https://ls1tech.com/forums/conversio...8l90-swap.html

Easiest, and cheapest way is to keep the gen5 accessories. All except the power steering pump. I made a simple bracket to use a type 2 PS pump in place of the vacuum pump. Switched to a zl1 balancer to have a full size rearmost pulley to drive the PS pump. Use the gen5 AC compressor with the factory ac. Use the gen5 truck radiator and fans - clean , simple and the fans move move air than any aftermarket ones. Mine even uses 2018 radiator hoses. Keeping it simple is the cheapest and in my opinion, BEST way.

[HYPR]

Originally Posted by barraza

http://67-72chevytrucks.com/vboard/s...d.php?t=819493

https://ls1tech.com/forums/conversio...8l90-swap.html

Easiest, and cheapest way is to keep the gen5 accessories. All except the power steering pump. I made a simple bracket to use a type 2 PS pump in place of the vacuum pump. Switched to a zl1 balancer to have a full size rearmost pulley to drive the PS pump. Use the gen5 AC compressor with the factory ac. Use the gen5 truck radiator and fans - clean , simple and the fans move move air than any aftermarket ones. Mine even uses 2018 radiator hoses. Keeping it simple is the cheapest and in my opinion, BEST way.

Really nice build brother! Interesting. This was my plan however everyone says the GEN5 LT1 AC Compressor being a variable displacement will not work with the '72 AC system (please enlighten me with the details how you addressed this issue). Regarding the PS pump I just bought the ICT 551-368-3 PS bracket (comes including a tensioner) and am installing the Type II PS pump aligned with the Alternator with the attached Reservoir and will run and off the shelf #1000K or 6PK2540 100" belt. Regarding the radiator in speaking with Tony at PSI why change out a Radiator that works just fine. Just install a set of twin 12" fans. Plumb the Steam port into the inlet and call it a day. Regarding the hoses I will do what I did with my Supercharged '56, buy some sections and stainless tubing. For the lower, 3-right angles and two stainless sections plus fabricate a bracket to hold in in place at the base of the fans. For the top something similar with an applicable angle of the Thermostat a short stainless section with a barb welded in place then another short hose to mount to the tub and radiator. I use the heat shrink clamps. They work great have been since their inception.

[Kermitt47]

The 2019/2020 trucks changed the water pump to a center mount like the LS and it keeps the VVT. They also added a PS pump for the 1 ton trucks with the new 6.6 L LT engines and hydra boost brakes. These will fit the earlier LT engines if used as an assembly. I have also heard that the AC pump an be used if it is wired properly to disable the variable displacement option. I will try this when I get it running.

[Joyridin]

Here is how you use the original LT/L83 compressor. It will work with no problem.

https://youtu.be/HMDBOPL9KSI

My L83 fit between the frame with no problem. I used a Type 2 P/S pump and added a remote fill. It runs the P/S and hydroboost and mounts where the vacuum pump was located and uses the vacuum pump belt drive off the balancer. Besides removing the vacuum pump, all the front drive was left the same. Here is a pic of the pump and the reservoir.

[barraza]

I used the new radiator and fans for several reasons. First, my radiator is original, 50 years old and has been repaired several times. Second, the new fans are controlled by the ecu, they run at whatever speed the ECU thinks they need to, from a gentle breeze to a hurricane. They also respond to AC pressures. They fit the 72 radiator support with some minimal cutting that cant be seen when installed. And the whole setup is cheap.

For the power steering i switched to the ZL1/CTS-V balancer to get a larger and wider pulley on the crank. My L86 vacuum pump used a 3rib pulley on the crank that was only about 3” in diameter. Most PS pumps are designed to run a little faster than crank speed, which meant i would need a very small PS pump pulley, about 2.5-2.75”. When i built mine, I couldn’t find any pulleys that small except alternator pulleys, which are designed to be be held on by the nut, not pressed like a PS pump. I built it and it worked, but poorly at idle. It also looked like a weak point because my truck is 4x4 with wide and heavy 35” tires. The zl1 balancer let me use a bigger pulley with a wider belt to run the PS, and the other pulleys are in the right place to run the other accessories in the factory location. Keep in mind that these engines idle at very low rpm, so the PS pump needs to have the proper ratio to give good performance at idle, especially if you have big tires.

[barraza]

I used the new radiator and fans for several reasons. First, my radiator is original, 50 years old and has been repaired several times. Second, the new fans are controlled by the ecu, they run at whatever speed the ECU thinks they need to, from a gentle breeze to a hurricane. They also respond to AC pressures. They fit the 72 radiator support with some minimal cutting that cant be seen when installed. And the whole setup is cheap.

For the power steering i switched to the ZL1/CTS-V balancer to get a larger and wider pulley on the crank. My L86 vacuum pump used a 3rib pulley on the crank that was only about 3” in diameter. Most PS pumps are designed to run a little faster than crank speed, which meant i would need a very small PS pump pulley, about 2.5-2.75”. When i built mine, I couldn’t find any pulleys that small except alternator pulleys, which are designed to be be held on by the nut, not pressed like a PS pump. I built it and it worked, but poorly at idle. It also looked like a weak point because my truck is 4x4 with wide and heavy 35” tires. The zl1 balancer let me use a bigger pulley with a wider belt to run the PS, and the other pulleys are in the right place to run the other accessories in the factory location. Keep in mind that these engines idle at very low rpm, so the PS pump needs to have the proper ratio to give good performance at idle, especially if you have big tires.

[HYPR]

Originally Posted by Joyridin

Here is how you use the original LT/L83 compressor. It will work with no problem.

https://youtu.be/HMDBOPL9KSI

My L83 fit between the frame with no problem. I used a Type 2 P/S pump and added a remote fill. It runs the P/S and hydroboost and mounts where the vacuum pump was located and uses the vacuum pump belt drive off the balancer. Besides removing the vacuum pump, all the front drive was left the same. Here is a pic of the pump and the reservoir.

OMG, THANK YOU! This was exactly what I was looking for. Simple and easy to follow even for an AC skill void guy like me...LOL. Now whether I keep the OEM AC system or upgrade to the Vintage Air will be a design choice not because I must do.

[HYPR]

Originally Posted by barraza

I used the new radiator and fans for several reasons. First, my radiator is original, 50 years old and has been repaired several times. Second, the new fans are controlled by the ecu, they run at whatever speed the ECU thinks they need to, from a gentle breeze to a hurricane. They also respond to AC pressures. They fit the 72 radiator support with some minimal cutting that cant be seen when installed. And the whole setup is cheap.

For the power steering i switched to the ZL1/CTS-V balancer to get a larger and wider pulley on the crank. My L86 vacuum pump used a 3rib pulley on the crank that was only about 3” in diameter. Most PS pumps are designed to run a little faster than crank speed, which meant i would need a very small PS pump pulley, about 2.5-2.75”. When i built mine, I couldn’t find any pulleys that small except alternator pulleys, which are designed to be be held on by the nut, not pressed like a PS pump. I built it and it worked, but poorly at idle. It also looked like a weak point because my truck is 4x4 with wide and heavy 35” tires. The zl1 balancer let me use a bigger pulley with a wider belt to run the PS, and the other pulleys are in the right place to run the other accessories in the factory location. Keep in mind that these engines idle at very low rpm, so the PS pump needs to have the proper ratio to give good performance at idle, especially if you have big tires.

All really great upgrades for your application. Gee I wish we had met years ago because I would have saved you a lot of hassle as I went though similar building my '56. The original engine was a 11.5:1CR so not enough vacuum to run PB so I installed a Hydraboost with a Wilwood MC back before it was the thing to do. I had the same problem with finding the proper sized pulley and found a source with both V belt and Serpentine style. The system worked great. Now that I have the Supercharged motor in I still kept the system because basically it just plan works and stops that 4500# barn on a dime with 9cents change.
Regarding the Radiator, good news is mine was replaced by the PO. Yep I will be installing dual 12" fans either Spal or Derali since I have great experience with both. I am looking for the maximum CFM I can get. The only variable will be if I just buy a premade shroud or if my son has time in his schedule to make me one or I have the time to go to his metal fab shop to fabricate one. Regarding fan controllers I spoke with Tony at PSI and they use the Dakota Digital to interface with the ECU to handle the either full hurricane mode or reduced speed or single fan whisper breeze speed. I have a three year old version of the Dakota Digital in my '56 and it works flawlessly so I am comfortable with this. My Supercharged 719HP '56 runs at 180-195 degrees even under load in 100 degree days. The highest temp I have seen was returning from Formosa Raceway on a 108 degree day with the AC blasting at boost it got up to 225 but quickly dropped back down to under 200 when the fans hit full tilt boogie. I run a large cross flow dual pass PRC Aluminum radiator on it. Thank you so much for all your advise and help. I can't wait to have this build done.

[Joyridin]

Originally Posted by HYPR

OMG, THANK YOU! This was exactly what I was looking for. Simple and easy to follow even for an AC skill void guy like me...LOL. Now whether I keep the OEM AC system or upgrade to the Vintage Air will be a design choice not because I must do.

The Vintage air makes the firewall look really nice and clean, but if my truck had factory A/C, I would keep it. $2500 just to clean up the firewall is a bit steep if everything you already have is able to work fine with the new pump. Just my opinion of course. I heard the Vintage system had a 20 week lead time now. I don't know if that is accurate, but you might want to check availability.

[barraza]

Originally Posted by Joyridin

The Vintage air makes the firewall look really nice and clean, but if my truck had factory A/C, I would keep it. $2500 just to clean up the firewall is a bit steep if everything you already have is able to work fine with the new pump. Just my opinion of course. I heard the Vintage system had a 20 week lead time now. I don't know if that is accurate, but you might want to check availability.

Agree completely. The vintage air system is not an upgrade to the factory system, and its not because of the AC function. It’s because the vintage air system is always recirculating air. In areas with mild winter temperatures it is great to be able to adjust the warmth of the fresh air entering the cabin without even running the fan. I had a vintage air system in a camaro and hated it.

[Hart_Rod]

I'm getting ready to do a couple of L86/8L90 swaps. Thanks for all the great info!