Join Date: Sep 1999
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Re: more questions about the 4.0 head swap
First, check if you even need to plug the triangle jackets on the manifold side by trial fitting. Many have sucessfully used JB Weld if needed.
The 4.0 is a FI head but can be carburated. If swapping in stock FI you will need the computer and it's wiring harness plus related hoses and charcoal canister. The primary hookup wires used are a constant hot(computer), an ignition-on (coil/fuel pump) hot plus the optional tach and check engine light leads. You will also need a FI fuel pump.
You can get an MPI's harmonic balancer and pickup sensor to take care of the ignition.
You can get away with a bigger cam because the 4.0 head helps solve the ping problem associated with MPI. I like my Hesco/Clay-Smith 214R grind.
It has been dyno tested and proven with this combination.
I've been told (by Hesco) that the 'no hot cam' disclaimer on the MPI kit was an effort to discourage radical cam installation due possable computer un-compatability and that they might worsen ping problems used in conjunction with the stock 4.2 head.
Can't answer the AC question.