LT4 8L90 feedback

[vet57air]

A couple friends and I bought our E-rod LT4 8L90 connect and cruise packages in 2019. One is in a 71 Blazer, the other is in a 70 Chevelle convert. Mine is in a 66 C10 that I call a Cgt. I got mine on the road this season where as the others are still progressing their builds. Thought I would start a thread to help those thinking about the same package and maybe have some questions that I have answered.
My Pro-Tour build is from the ground up. Full custom chassis to my specs. Our LT4 packages came with engine and trans ecu's and wiring harness. I mostly followed GM's recommendations. The exception was tire size. They say axle ratio calibration is set for 3:42 and is suitable for 3:08 to 4:11 and tire size between 26" and 30". The rear tire I installed is 31" and I went with a 3:73 gear. I figured the trans just monitors input and output speeds so by going over in tire height the gear I chose would allow it to still be in range.
At 70 mph it does about 1800 rpm.
At 30 mph it does 1000 rpm.
Things I like- Good fuel economy
- Great power 650hp 650ftlb torque
- anyone can drive it, idles smooth
- Love that blower whine when you put your foot in it.
Thing I don't like- little traction
The trans has P R N D M. My manual is controlled with paddle shifter from PCS. I wish GM had a full auto sport mode. As I find when going at 30-50 mph going up a mountain it seems to be lugging. I find at full throttle you go faster
in D as it takes the engine to redline and shifts (it happens fast). Going through twisties the manual mode is great and rev matches going down.
Would like to hear feedback on other LT4/auto/man. owners experiences.

[DualQuadDave]

Not to be negative, but I would at a minimum watch what oil you put in your LT4. I have seen soooo many blown up LT's including my 2018 Yukon bought new w/ perfect Mobil 1 oil changes. The bottom ends are built super tight and the lifters are junk. I have no idea what sort of warranty they give on the crate motors, but I would research it and have all the paperwork ready for JIC. Might give Lingenfelter, Katech or BTR a call and just ask what they recommend for preventative maintenance/upgrades. Those are the only guys I would trust to touch an LT, and this is coming from someone who builds motors ground up.

PS: If your buddy with the 71 Blazer decides to not finish his project, I am looking for one. Thanks!

[Vegas69]

I seriously have to wonder about the thin oils all the manufacturers seem spec these days. My understanding is that it's for a miniscule amount of efficiency. My 2017 Tundra with 55k needed new lifters from a sporadic tapping like and old chevy small block. It runs 0w-20. Now the manufacturers are extending the oil change intervals as well. That's a bad idea in my opinion. Most of us commute fairly short distances which as we all know isn't a positive thing for less frequent oil changes. I plan to change the oil in my Tundra at 5k even with synthetic. Not only have the manufacturers specified lighter oil viscosity, but they have also put less tension in the rings to again, aid in efficiency. It's a recipe for far less longevity from my perspective.

[DualQuadDave]

I seriously have to wonder about the thin oils all the manufacturers seem spec these days. My understanding is that it's for a miniscule amount of efficiency. My 2017 Tundra with 55k needed new lifters from a sporadic tapping like and old chevy small block. It runs 0w-20. Now the manufacturers are extending the oil change intervals as well. That's a bad idea in my opinion. Most of us commute fairly short distances which as we all know isn't a positive thing for less frequent oil changes. I plan to change the oil in my Tundra at 5k even with synthetic. Not only have the manufacturers specified lighter oil viscosity, but they have also put less tension in the rings to again, aid in efficiency. It's a recipe for far less longevity from my perspective.

I agree 1000%. That 0w-20 is a joke. It's like water when cold, you can imagine how thin when hot. Did you know GM's min bearing clearance in the book is .001? That's insanely tight. On my Yukon, I found out the hard way they changed the warranty to 60k from 100k like the LS days. A$$holes. I think the engineering on the LT's is pretty amazing, but the execution didn't go as planned. JMO, don't flame me on that one, I am going what I am seeing on the street/forums. I have seen plenty of 300k LS's, have yet to see an LT anything make it even half that on a large scale.

[vet57air]

All good info to consider. Our crate warranty was 2 years. Unfortunately when your project is from the ground up many take longer then 2 years. Running syn. 5-30w presently as per GM manual with about 2000 miles. (I haven't beat on it to hard yet) Likely will go syn. 0-40w on the next change when I put it away for the winter.

[srode1]

Curious, did you use Dexos II synthetic as your break in oil at start up? Old school is don't use synthetic for break in but I think GM delivers new LTs with Dexos from the get go now days.

[vet57air]

Curious, did you use Dexos II synthetic as your break in oil at start up? Old school is don't use synthetic for break in but I think GM delivers new LTs with Dexos from the get go now days.

I followed GM instructions. Used Mobil 1 Dexos 5-30w. Prelubed, then started and drove about 50 miles and varying loads under 4000 rpm. Changed oil/filter. Drove another 500 miles and changed oil /filter. Have about 2000 miles and maybe will put another couple hundred before I put it to bed. Will change oil and filter again at that time. Point of interest, when I tried to start the first time, it wouldn't. I read further down the instructions which described the "soak and idle". Which is basically connect the battery and let sit for 8 hours, then start. I let it sit over night and it started immediately.

[Vegas69]

I agree 1000%. That 0w-20 is a joke. It's like water when cold, you can imagine how thin when hot. Did you know GM's min bearing clearance in the book is .001? That's insanely tight. On my Yukon, I found out the hard way they changed the warranty to 60k from 100k like the LS days. A$$holes. I think the engineering on the LT's is pretty amazing, but the execution didn't go as planned. JMO, don't flame me on that one, I am going what I am seeing on the street/forums. I have seen plenty of 300k LS's, have yet to see an LT anything make it even half that on a large scale.

I'm not surprised. New vehicles are getting far too complicated for my taste. Every ounce of efficiency pursued and every gadget under the sun that will fail over a long duration. I think we'll end up with a 4 Runner for my wife. It's still the same platform from a decade ago with a powertrain that has been around for 17 years. I'm in the minority I realize, but I like that!

[srode1]

Point of interest, when I tried to start the first time, it wouldn't. I read further down the instructions which described the "soak and idle". Which is basically connect the battery and let sit for 8 hours, then start. I let it sit over night and it started immediately.thanks for sharing that - I need to reread my instructions, I don't remember seeing that but guessing it's in there for mine too. Did you get any codes when it wouldn't start before the 8 hour soak?

[vet57air]

thanks for sharing that - I need to reread my instructions, I don't remember seeing that but guessing it's in there for mine too. Did you get any codes when it wouldn't start before the 8 hour soak?

No codes. I hadn't cranked on it for very long, expecting it to start right away. Went back and read farther and found the "soak and idle". Ideally GM should put that note in before the start-up and breakin procedure, not after.

[Jimbo1367]

I followed GM instructions. Used Mobil 1 Dexos 5-30w. Prelubed, then started and drove about 50 miles and varying loads under 4000 rpm. Changed oil/filter. Drove another 500 miles and changed oil /filter. Have about 2000 miles and maybe will put another couple hundred before I put it to bed. Will change oil and filter again at that time. Point of interest, when I tried to start the first time, it wouldn't. I read further down the instructions which described the "soak and idle". Which is basically connect the battery and let sit for 8 hours, then start. I let it sit over night and it started immediately.

IMO the oil change regiment it perfect for a new engine. I see way to many people buy a new car 20-70K, then do the first oil change at 5; 7 or 10 k miles. Toyotas do this a lot. Most of the Toyotas I see have some sort of engine noise. It doesn’t matter how low the miles are either. I bet these guys only lease their vehicles so they don’t care about all of that trash running trough their motor. Someone else will own it soon enough. LOL.