4.2/4.0 hd/MPI leave as is or go forced induction?

4.2/4.0 hd/MPI leave as is or go forced induction?

Zuni

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South Lake Tahoe, CA
Vehicle(s)
84 CJ7, 03 WJ
I'm still gathering all the parts to put a 4.0 head on my 4.2 with Mopar FI. I was hoping to have it done by now, but life gets in the way of progress sometimes. My plan is to start the transformation next Winter and it would be nice to have a second engine to build up and still drive the CJ. I'm kind of thinking of also adding a turbo or supercharger to it (low boost), but I'm not sure I want to get into a situation of project creep. I've done my own turbo kits before and have had a couple of supercharged cars, and also designed several supercharger applications for OEMs in the past so I'm comfortable with either. My gut feeling is don't do the forced induction now and just get the engine in the CJ with the head and MPI set up and then decide on what to do. But, if I do it all at once it will be easier to fab everything up out of the Jeep. I'm probably more comfortable doing the turbo and I can get the turbo at cost (I've worked for Turbo manufacter for the last 15 years) and have lots of connections. A supercharger will actually be easier to install but will cost me more money overall. The whole debate over turbo vs. supercharger is non issue as they will both accomplish the same thing only in slightly different way. The problem most people face is not sizing the turbo properly for a particular application, and use Uncle joes turbo he took off a John Deere 10 years ago, and then wonder why it has too much lag. At that point there opinion is all turbos are no good especially for a 4x4. If I go supercharger it will probably be a Rotrex http://www.rotrex.com/, if I go turbo it will be a Garrett Welcome to TurboByGarrett.com ball bearing with a water cooled center housing. Either one will have a charge cooler and to keep plumbing eisier it will probably be air to water. Once i decide to do a turbo or supercharger I'll do a write up but right now if you were me what would you do?
 
Nice write up... You want the short answer or the thorough one? Probably the short as you know allot about compressing intake gasses (LOL)...

With a good low inertia TC you can't go wrong... Lag is almost nonexistent and you do not have the HP robbing belt...

It has been a long time since I did ant TCing, how common are variable vane TCers now?

BTW - The 390 I have in my CJ right now is o-ringed... I always wanted to go to a dual route... Two small ones - one for each bank!

BTW - My only reservation for a TC is when I immerse my CJ in water up to the intake! It has and will happen again!
 
With a good low inertia TC you can't go wrong... Lag is almost nonexistent and you do not have the HP robbing belt... You're absolutley correct.

It has been a long time since I did ant TCing, how common are variable vane TCers now? Not that common, there are only a few applications that use those.

BTW - The 390 I have in my CJ right now is o-ringed... I always wanted to go to a dual route... Two small ones - one for each bank! Right On!. That would work very well.

BTW - My only reservation for a TC is when I immerse my CJ in water up to the intake! It has and will happen again! Not a problem for me as I avoid deep water.
 
If you add the 4.0 the compression is raised. Unless you plan to compensate for that.

Keep the 4.2L and add a junkyard TBI setup.
JY TBI is a chevy 4.3L throttlebody, engine harness, and computer.
You can do it yourself for less than $500.

Then jam the TC or SC on it and roll.

On a side note the howl of a TC or SC through a snorkle is awsome.
 
Nothing quite like hearing the whine of a turbo;)
 
If you add the 4.0 the compression is raised. Unless you plan to compensate for that.

Keep the 4.2L and add a junkyard TBI setup.
JY TBI is a chevy 4.3L throttlebody, engine harness, and computer.
You can do it yourself for less than $500.

Then jam the TC or SC on it and roll.

On a side note the howl of a TC or SC through a snorkle is awsome.


Instead of the junk yard TBI I'm going to do the MPI. I picked up an unopened kit that someone bought and then sold their CJ before they installed it. I picked it up for a song (less than a new Howell kit) so I it's going on the 4.0 head. I also picked up a 4.0 head recently and it's ready to go in as well. I still need to to gather up a head gasket, head bolts, and other misc stuff. Oh and I scored a new Banks header for less than half price as well. If your patient and search eBay and Craigslist daily you can find some good bargins.

As far as turbo vs. supercharger goes the exhaust becomes much easier if you do the supercharger. I have located a new cast manifold for a 4.2 that has a T3 flange on it for a turbo but the price is too high at his point. They want $800 for it, so we're very far apart on the price. I could fab one up or run a pipe from the header to the distributor side and mount the turbo like they do with the 505 kit. I just need to think through all the options and decide what makes the most sense. The Rotrex SC would be a real clean install. That's the one HESCO uses on there kits and it works great for low boost.
 

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