• Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.

Opening up a can of worms, but what is the thought on 4.0 head w/ carb?

Highlights Only
Opening up a can of worms, but what is the thought on 4.0 head w/ carb?
I saw nothing mentioned about a crank position sensor, did you use one?
 
IOPort51 said:
I saw nothing mentioned about a crank position sensor, did you use one?
Click to expand...

You have to with the 4.0 MPFI. It is integral to the control system, the ECM will not fire the coil if there is no CPS signal.

This is probably the biggest hurdle in going MPFI, you have to have the CPS which means you either have to buy a relocation kit from HESCO or you have to go with a 4.0 Transmission and flywheel/flexplate. Neither are cheap.

I have heard that it may be possible to swap out your flywheel and modify a AMC 258 i6 / 4.2l tranny bellhousing to accept the CPS but that is a huge PITA as well.
 
So what did Tinman do? I see no mention of changing the Transmission or the flywheel.:cool:
 
The TBI is looking better all the time.:D

That is an incredibly slick job with the hall affect sensor.:rock:
 
just to add to what was already said by others, and to keep on track with the poster's original question....

When I did the head swap, I kept it carbed, mainly for simplicity. My original setup was a Weber on the AMC 258 i6 / 4.2l head. I had already built the engine up with high compression pistons and a cam, hotter ignition, but the AMC 258 i6 / 4.2l head was restricting me severely.

So with the head swap, I used a Clifford aluminum intake designed for the 4.0 with a carb application. And on that I used a 500cfm Edelbrock 4bbl. The power increase was amazing, and Im convinced most of it was the head flow (the Edelbrock would have just choked out the AMC 258 i6 / 4.2l )

So yes. The addition of the 4.0 head whether you keep it carbed or go FI is a HUGE power improvement over the AMC 258 i6 / 4.2l head, as others have said.
 
IOPort51 said:
The TBI is looking better all the time.:D

That is an incredibly slick job with the hall affect sensor.:rock:
Click to expand...

If you are buying a brand new from the store kit then maybe I can see why the TBI would look better but if you are either doing a Junkyard conversion or buying a used kit off of someone I can guarentee the MPFI is going to be a much smaller headache and a much better bang for your buck in performance gains.
 
there are a couple major changes and a few smaller things on the list before the EFI is going to happen But you have been a great help. thanks.:chug:


ThisGuyUKnow said:
If you are buying a brand new from the store kit then maybe I can see why the TBI would look better but if you are either doing a Junkyard conversion or buying a used kit off of someone I can guarentee the MPFI is going to be a much smaller headache and a much better bang for your buck in performance gains.
Click to expand...
 
IOPort51 said:
there are a couple major changes and a few smaller things on the list before the EFI is going to happen But you have been a great help. thanks.:chug:
Click to expand...

Io let me be your guide to fuel injection! I have more schematics and notes on the swap than you'll knew what to do with!
 
I am over due for a trip to have a ride on a dyno, never have.
I am thinking seriously about the grave yard GM TBI. Strangely enough I have picked up a flywheel required for the MPI and I have an adapter for a GM TBI, things could fall either way. I would like to compare the dyno graphs between a TBI and Tinmans MPI.
I have to say his numbers are surprisingly substantial. I had expected some low speed torque improvement but 50 lb/ft is remarkable. I would very much like to see what a similarly built TBI would do.:cool:
 
IOPort51 said:
I am over due for a trip to have a ride on a dyno, never have.
I am thinking seriously about the grave yard GM TBI. Strangely enough I have picked up a flywheel required for the MPI and I have an adapter for a GM TBI, things could fall either way. I would like to compare the dyno graphs between a TBI and Tinmans MPI.
I have to say his numbers are surprisingly substantial. I y had expected some low speed torque improvement but 50 lb/ft is remarkable. I would very much like to see what a similarly built TBI would do.:cool:
Click to expand...

Will you be using just the fuel control of the tbi or will you swap the spark control as well? The electronic spark control is a huge advantage of the fi over the vac advance.

You will need to reflash/tune the tbi ecm to get good results.
 
Is that what you called a damper in your parts list?:cool:
 
I am getting ready to pull the AMC 258 i6 / 4.2l out of mine and I am thinking about doing the head swap. I would love to do the FI conversion, but the wiring scares the hell out of me.
 
C dubya said:
I am getting ready to pull the AMC 258 i6 / 4.2l out of mine and I am thinking about doing the head swap. I would love to do the FI conversion, but the wiring scares the hell out of me.
Click to expand...

I can give you all my notes and diagrams and work you through it or you can buy one of my harnesses.
 
I like your harnesses. I have made my list of parts I need to aquire. It seems it has been done enough now that I could figure it out over time. Now the parts hunt can start.
 
You must log in or register to reply here.

Jeep-CJ Donation Drive

Help support Jeep-CJ.com by making a contribution.

Help support Jeep-CJ.com by making a contribution.
Goal
$200.00
Earned
$0.00
This donation drive ends in
0 hours, 0 minutes, 0 seconds
  0.0%
Contribute
Back
Top Bottom