I have reached a dead end with fixing the chirping, vibrating and popping. BoostedTech is entirely unwilling to work on my unit even at my cost (I'm honestly not sure why they had me send them the unit if they weren't going to check the inner-workings of it). I have not found any reputable companies able to work on the M90 SC. To continue further will require throwing parts at possibly both the engine and supercharger until something sticks and fixes the problem.
My long term plans have been to build a supercharged inline 6 stroker to get 350-400HP. At that time I would need to replace the transmission to a "heavy duty" built 42RLE such as one from ATS Diesel. Since I'm also unhappy with the 2.72:1 ratio in the transfer case I've decided on an Atlas case which will require 2 new driveshafts.
And if I'm building up and spending money on the transmission, transfercase and driveshafts I want to be sure I actually want to stick with the inline 6 engine platform.
So far I'd say that I'm content with the power provided from the supercharged stock 4.0L on my 37s. It returns my Jeep on 37s to roughly feeling like driving stock on 30s and I can maintain highway speeds no problem. It runs 0-60 in 10 seconds and gets between 9MPG if I drive aggressively to 12MPG if I drive gently. Wanting more power is because I enjoy building and it puts a smile on my face.
Sticking with the inline 6 and 42RLE makes swaps and upgrades a plug and play weekend project and can be done incrementally which is convenient and I can still have my Jeep ready to go for trips. I also think the legacy inline 6 is kinda quirky and fun and how cool would a built I6 "LS killer" be?. But it's an outdated platform without a ton of aftermarket support like some other platforms have received. If I really built it up, it'd cost around $8000 for a 270HP 4.6L stroker, another $7000 for a supercharger with more volume than my current M90 to add another 75HP, plus a built 42RLE transmission for $3500 to handle it, which brings the total to $18,500 for less than 350HP pushing it to the limit with no room to safely add more HP. The downside is that this engine wasn't designed for high horsepower and pushing it that hard, especially in hot weather, may require meth injection which is not something I really want to get into since I'm looking for dead nuts reliability. Additionally after this past month of trying to diagnose my current issues I'm realizing that there just isn't much help out there for the inline 6 — and I fear that issues will come up going forward. I enjoy building, I don't enjoy diagnosing engine issues.
Which brings me to the V8 LS and Hemi platforms. These have a strong following and extremely good aftermarket support. Even 50 years from now these platforms will (hopefully) still be well supported. A low mile 350HP 5.3L LS engine including transmission costs less than $5000 with all of the required supporting parts, gauges, brackets, exhaust, etc to fit it into a TJ and do it right. Compare that to the similar horsepower from the I6 stroker build for $18,500. And from what I'm learning another 50HP can be easily added to an LS with reliable mods for only a few hundred dollars in parts and if I'm ever really itching for more HP a low boost supercharger can add another 100-140HP safely for $5000. Point being that for 2/3rds the cost of the 350HP I6 stroker I could have around 500HP and not even be pushing the engine to it's limit. The downside is that this means considerable time my Jeep needs to be stuck in the garage for in order to do it right which will be compounded due to the time it'll take for me to learn what I need to do (I've never swapped an engine before).
If I make the decision now, before upgrading my 4.0L further, I will not have wasted much time or money but if I start building what I have and later decide to switch it's going to be a very costly mistake. I have a lot of consideration to do.
