Fueil injection for the 4.2 to 4.0 head swap - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 08-27-2002, 12:08 PM Thread Starter
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Fueil injection for the 4.2 to 4.0 head swap

Has anyone done the 4.0 conversion and used the FI from the donor vehicle. I want the power and reliability but I don't want to drop 2k for the mopar MFI and another 200 for a vibration damper. I have an 87 YJ with a weber carb on it now, stock manifold and stock exhaust. What are my options? Can I reuse the weber on the new head? can I keep the same valve cover or do I need to change that out also? Thanks...
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post #2 of (permalink) Old 08-27-2002, 12:54 PM
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Re: Fueil injection for the 4.2 to 4.0 head swap

I haven't done this swap, but have read a fair amount about it here and other places. Here's my input:

You can use the FI from the donor vehicle. Make sure you get the head and intake from a '92 and up vehicle, the wiring changed signifigantly (for the better), also '92 and up heads are the HO style, better flow than previous versions. You still will need either a new damper or a bellhousing with a provision for the CPS to run FI.

If you want to stick with the Weber, then you can reuse your stock intake manifold and use a 4.0 exhaust manifold/header. The 4.2 intake matches up, but the exhaust won't, mandating the use of 4.0 components.

AFAIK, you'll have to use the 4.0 valve cover as well.
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post #3 of (permalink) Old 08-27-2002, 01:58 PM
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Re: Fueil injection for the 4.2 to 4.0 head swap

TBI conversion is also an option if you decide not to do the MPI from the donor 4.0
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