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post #1 of (permalink) Old 09-12-2000, 12:43 AM
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more questions about the 4.0 head swap

After doing some research I have decided to do the 4.0 head swapp on the 258 in our 84 cj7. I have a couple more questions that I would like to ask. I noticed that the a/c pump bracket bolts to the head. Will the new head have these mounting holes? Also what kind of epoxy should I use to to plugg the water jackets that arent used in the head? Since we are rebuilding the whole engine will this upgrade work well with a larger cam? And for the last question, we havent decided to go fuel injection or not but if we do what other parts will I need from the donor vechile to make it work besides the intake?
Thanks again for the help of this board.

81 cj5 WITH SOA/SR/302
2000 TJ


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post #2 of (permalink) Old 09-12-2000, 10:37 AM
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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.

Jaffer is offline  
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