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Does anyone have any advice running stock exhaust with a mild cam in a 4.2?
My project is a 1980 Cherokee Chief with the old inline six, i would install a
header but i cant seem to find one that will clear the front driveshaft.
the cam is a COMP Cams CL68-201-4 for those wanting to know.

So 1980 was a crossover year. Do you have the cast iron intake or the aluminum one? Typically there is 79 and older, and 81 and newer. 80 was kind of a mix depending on when it was built.

The aluminum intake (and the exhaust manifold that was used with it) flow a lot better than the older cast iron intake and exhaust that was used with it.

The latter exhaust is not as good as a header, but is better than the early one. If you have the older one, it’s worth tracking down the later version.

i have the cast iron intake/exhaust. is there a specific year that i can find the aluminum exhaust or would you know of a header that could clear the driveshaft? i have a 6 inch lift maybe that would be enough to get away with one of the short pipe headers. just want to be sure before i spent the cash and labor.

IIRC '80 is the last year for the "heavy" 258. Should be the same as the '79 and earlier engines. I have never heard it described as a mixed year; instead a clear change for 1981.

Agreeing you could use the '81-up manifolds. In '81, the 258 was freshened up with a lighter block casting, new lighter and more efficient manifolds, plastic valve cover, and a lighter crankshaft with fewer counterweights. The newer manifolds will bolt on, and should be no problem with the driveshaft on that side. The newer exhaust manifold is much smoother and less restrictive than the older type.

I have some '85-ish manifolds from a CJ-7 on my '77 J10. Any 258 1981 or newer will have the newer manifolds. No changes needed other than installation of the new manifolds and a small notch in the steel power steering bracket for clearance. You lose the exhaust heat flap between the manifolds, replaced by an electric carburetor heater. Depending on your location, you may want to enable that for better cold-start performance.

Not sure about a header. Most of the market for these headers is for CJs, which were always passenger drop. The YJ Wrangler got the 258 '86-90 and is driver drop as I recall. A header for that model might work, though there are a lot of dimensional differences between the Wrangler and your Cherokee.

Another possibility is to switch to the 4.0L head, either the earlier one or the '91-up HO type. These come with a header from the factory, and can accept the aluminum 258 intake. No personal experience with these, but there is plenty of coverage of this topic on the internet. There is a lot online about putting the 4.0L HO head on the 258 block. Supposedly much of the power advantage of the 4.0 HO head on the 258 comes from the increased compression, and the '83-90 4.0L head has a similar compression increase. Recall the hot rodder's 4-Cs: cam, carburetion, compression, cubic inches.

tgreese wrote: ↑Mon May 24, 2021 6:56 am IIRC '80 is the last year for the "heavy" 258. Should be the same as the '79 and earlier engines. I have never heard it described as a mixed year; instead a clear change for 1981.

To my knowledge, later 80's did get the aluminum intake, as I have seen one. But not really important here, just wanted to verify which one he had.

I would never say never when it comes to Jeep. One can imagine plenty of reasons why Jeep would have switched over to the new design when the parts and the factory were ready.

I looked at the '80 parts book and there's nothing about the updated engine. Strangely, the '80 engines have their own part numbers for crank, valve cover and manifolds. But there's nothing to suggest a split within the year. Critical missing parts are missing that would not be on the earlier engines, such as the exhaust gas tube between the manifolds and the electric heater in the intake. Just FYI. There could be a supplement that I'm missing.

thanks for the info guys, will see if i can hunt one down in a junkyard.