Header on 258

Need help Header on 258

I have a 75 cj5 with a 258 and an offenhauser intake with a Holley 390, my neighbor gave me a pacesetter header for free and the header gasket is coming in today. I have noticed the factory exhaust manifold helps hold the intake in place so am I going to need special bolts or some kind of clip to hold the intake in place and does anyone have pics of the engine compartment that I can see how this is done. Once again I am new to the jeep world so just need some advice all I have ever worked on is bikes and a v8 or 2.

 

As long as you can fit the header with the manifold in place, you don't need any connection between the manifolds. The 4 bolts that connect the manifolds seal an exhaust passage to the intake manifold. This exhaust passage provides heat to the intake for warm-up and in extreme cold weather.

Usually you have to cut part of the 4-bolt flange off of the intake manifold to make a header fit. The flange is pointless with a header anyway, since the header cannot supply hot exhaust gaas to heat the manifold.

 

I ran an Offenhauser Dual Port and Holley 390 with a set of Adapters headers on my 258 a while back. I could never get the thing to idle properly and the gas mileage went down the tubes big time. The guys at the local speed shop said I was having a fuel puddling problem because of the way the headers were mounted using an extra gasket . I removed the dual port manifold and 4 barrel and went back to my stock carb and manifold while still running the headers. There was still better throttle response than stock with just the headers on but the darned thing kept loosening causing exhaust leaks at the head. I could figure on having to replace the header/intake gasket once a year or so. I eventually said the hell with it and went back to my stock exhaust manifold. I think I get about the same performance increase that I realized from the headers with my DUI dizzy.

 

Just a comment - I would not spend a lot of money on a header or fancy manifold for a 258. The 258 head is very restrictive compared to the 4.0L head. You can even buy a brand-new 4.0L HO head for about $500, and you'd be hard-pressed to buy a carburetor, fancy intake manifold and header for that much.

This also means that the 258 pieces go-fast pieces aren't worth very much on the used market... if you already have them, go ahead and use them, but I would not spend any money on 258 induction and exhaust.

There's lots and lots of info about junkyard upgrades for the 258 online, BTW.

 

Thanks guys well i guess i will just stick with the stock exhaust manifold then and send this header gasket back.

 

4.0L head on a 258: http://www.monsterslayer.com/pages/jeep/40Head/40Head.htm

 

Thanks this will be good restroom reading, and thanks for all the help this web site is awesome everyone has been great.