OK, so I have my 78 Cj7, and it runs pretty well, It has the howell FI on it now, but just doesn't have the power I'd like. I understand that swapping to a 4.0 head will really help, I need to know what I do for exhaust and intake, will they need to be swapped as well? I would like change to a header too in the process. I HAVE TO PASS CA SMOG, Someone in the hardcore area gave me some infor but I can't find it now.Thanks, Frank

I believe the only part you will need to change in the header, it will have to be one for a 4.0. The intake will cross over fine.

The tubular factory headers actually aren't that bad flow wise (asides from the cracking issues). You won't gain anything going to aftermarket performance headers except for a lighter wallet. Pick up a set of the remanned factory headers with the expansion joint thingies. Should be <$100.

You won't be able to use your 78 intake manifold. You'll need something off of a later model CJ, or an early Wrangler.
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Do a search for user name yj and corey He has done a lot with those engines and is pretty informative. some good reading and info.

I'm searching this too! I will put on here what I find. Heres something;

http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=277013

I did the headswap a while back but I went with a Clifford intake. My understanding is if you use the 4.2 intake, you have to modify the dowl pins and do a bit of grinding.
I used a stock XJ header and it worked awesome.
Topped it all off with a 500cfm Edelbrock and the thing ran unbelievable. A huge power increase. I already had high compression pistons, an aftermarket cam, and a TFI ignition upgrade, but I could tell the difference between the performance of the heads.

Another

http://www.hescosc.com/shop.asp?action=details&inventoryID=45290&catId=7758

and another;

http://www.northeastsurf.com/4.0%20head%20swap.htm

you might need these;

http://store.summitracing.com/partdetail.asp?part=TFS%2D51400419%2D1&N=0&autoview=sku

I've already done this on a 79 258, so I am not guessing when i say

-You won't be able to use the 78 Intake. You'll need a 80's CJ or early YJ intake.

-Factory 4.0L HO headers flow fine, they just crack. Get some remanned ones and save yourself money. I have no idea what you need to pass you Commiefornia laws.

-79 and down 258s have 1/2 head bolts same as the 4.0. No bushing thingies needed.

-Run the correct spark plugs. The 4.0 plugs are too cool and will foul with a carbureted motor. Don't know what you'll need for the Howell. They'd probably be able to tell you.

-Pushrod length is important. Measure the lifter preload and get the correct length push rods.
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