AF Intake/Headers, are the worth the investment????

I have an 83 CJ7 with a .030 over 4.2 with a Howell TBI set, with a GM Dui distributor.
I’ve been debating some time if an Aluminum Intake and Header would help or hurt.
The Sept issue of JP notes a user had an almost stock 4.2L.

Would be interesting to have JP run a review in the Magazine to see if it’s “all that”.
Or have they??  

Intake manifolds do not build power in a way that most people think. It is better to think about intake and exhaust manifolds as tuning power, not building it.

The size and length of the runners dictate when resonance will occur. Resonance is what builds a little power because the air is flowing faster than it would be if it were not resonating. But resonance only happens in a very narrow rpm range for any given manifold design.

There are also pulses that happen inside a manifold that are caused by the valves opening and shutting. If the pulses are tied together inside the manifold, some scavenging can happen. The scavenging that happens in the intake manifold is timed with the cam profile. That's why cams and intakes should always be matched. But the scavenging that happens in the exhaust has more to do with tube size and length before it enters the collector.

Headers can be more independent of the engine internals.

The cross-sectional area of the primary header pipe affects the location of an engine's torque peak in the RPM band. The pipe length generally will not change the peak torque or the RPM at which it occurs. A length change has the effect of improving the torque on only one side of the peak by "borrowing" it from the other side. A shorter pipe improves torque after the peak (reduces it at lower RPM), preventing the torque curve from falling off so quickly as speed increases. A longer pipe extends the torque curve backwards to improve the engine's flexibility, at the expense of after-peak torque.

So in a nutshell, headers really just move power around in the rpm range and there will be a compromise. Intake manifolds can help with power but only in a small rpm range and is heavily dependant on the cam profile.

Messing around with manifolds may help or may just make drivability suffer. Certainly you'll be giving up something to get something. The 4.2 is not a race motor and is not capable of turning high rpms and therefore big horsepower numbers. It takes rpms to build horsepower. The 4.2 is an under-square design that is meant for low rpm torque production.

Manifold changes are most beneficial when you have more air running through them and that only happens with high rpms.

If you want a high rpm, high hp race motor, the 4.2 is a bad platform to start with.

You've done the best things that you can do to the 4.2. DUI ignition and fuel injection make the 4.2L a great Jeep motor. Enjoy it!