Headers and Mopar MPI Kit

It works fine with the RIGHT header. If you have a header that was for your carbed 4.2, it may or may not fit. The flange may interfere with the mounting of the EFI intake. If you really want to see the full potential of the EFI kit however, do yourself a favor and pick up a '92 to '95 4.0L cylinder head and install it in place of your 4.2 head. Of course if you do this, you'll have to replace your header with one made for a 4.0. Borla makes a great one. Check out Tim's 4.0L head conversion write-up on the subject. From what I've seen and heard, the new head makes a world of difference and lets the EFI work even better. Since you'll have the whole thing apart anyway, why not... it's only a few bucks at the wrecking yard, just make sure you pick a good one (for a few bucks, a machine shop should be able to perform a thorough check for you). Good luck, and let us know how it goes.

-Spyder

I purchased a header with the MPI. Because a installed the 4.0 head, I needed a new exhaust manifold. Protech out of Denver sold me the header with the MPI.

Good luck, On mine, I could not be happier.

Enjoying Montana's Big Sky (& rocks & rivers & mountians etc, You get the picture.)

The Mopar kit works well with headers. I used a Borla header on one CJ-7 with no problems other than the cheap gasket supplied with the header. I did have to relieve an area of the intake with a file at a point of minor contact with one of the tubes. You won't know until you try it. It definitly will fit with your stock manifold if you still have it. If you do get the 4.0l head, and don't wish to buy another header, get the stock tube exhaust manifold with the head, it's not too bad compared to the 4.2l iron part. Semper fi.

What is the diameter of the end of these different headers? how well will the 4.0 head on a 4.2, plus header, plus MPI take care of v8 envy.
Thanks
Tas
'89 YJ I6