New to the straight six

Ok guys so i have a 1980 amc spirit with the 258 and a 3 speed auto.
I want some more power out of it no more than 300hp just because i want it as a driver too
Some of the things im looking into: the clifford intake with weber 38 carb and clifford dual exhaust header but after some research im not sure what i want to do

I guess my main question is where is a good place to start on the 258 (i want to keep it instead of swapping)

I thought about doing a 4.0 head with better intake and exhaust and upgraded fuel injection or carb and upgrading the ignition... do you think that's a good start? I'm new to the straight six and i want it to be a fun driver with enough power... i might add im not looking for top speed im more looking to have fun at a red light or two... i like the low end from the 258 and want to build off of that

Edited by Nick_m - Aug/29/2014 at 3:17am

If you want to
A. Keep the 258
B. Install 4.0L head
Then I would
C. use a 2002 up 4.0L head
D. Use a Clifford, or Offenhouser dual port intake, perhaps a 2000 up efi intake swapped to carb? I've not seen any flow results with the last one, but it has been done.
E. Find a set of what I call "bundle of snakes" 2000 up dual outlet shorty header.

The bundle of snakes header is designed to work with the 2000 up head and even though the head has smaller exhaust ports some have stated it flows the best.

And of course a cam of your choice.
300hp? I doubt it, but it will run good once you get it all sorted out.
I would add that I would go with a 97-99 4.0L shortblock if I could fine one and the 2000 up head, being careful to avoid the ones that tend to crack. I forget what design symbol is but there was a redesign in 2002 and a lot of 2000-2002 engines were fixed with the newer head.

Illnois doesnt test anything older than 1996.

The 4.0L swap sounds best to me too. You can use the factory headers, and that'll save some $$.

With a more agressive cam and a Clifford intake it'd be alot of fun. You'll need an electric fuel pump, and may want to switch to a 258 water pump to run a V-belt.

Look to Sixpack for good tips - few people have built this engine to the level that he has.

FSJunkie wrote: 258 + 4.0L = 4.6 stroker. Only thing I don't like about 4.0L's is they're noisy and don't produce good torque until 3000 RPM. All the Jeep guys love to say "...lots of low RPM torque..." when it comes to a 4.0L, but those that do have never driven a 258. I'd have to look at the torque curves, but I wouldn't be surprised if the 258 out-pulls the 4.0L below 2500 RPM. 258's just fall on their face above 3500 RPM. 232's rev out a little better.