Exahust options for 258

[Florida83FSJCherokee]

Ok , Im going to replace the exhaust system and need some advice from you guys with "tuned up" 258's. (no laughing 401 guys!)

Im running a 2100 motorcraft , duraspark HEI, plugs gaped at .35, no air, and no emissions. Before I replaced the carb it seemed like everyone was playing well together, but now with the new carb and the timing pushed up a bit I have a rocket! for a 6 cylinder, but I feel like the exhaust isnt getting out of the system fast enough... It just feels overpressurized when you get on it... then when you downshift or let off of it sucks and crackles...

the current exahust is old, the manifold gasket is leaking at the rear two bolts, the cat is original.. i think, and the muffler is a flowmaster of unknown install date... So basicly Im gonna redo the whole thing.

My questions for you guys:

Manifold:

Should I replace the manifold? or just the gasket?
If so is the one that BJ's carries worth the extra for the "dog leg port design"? http://www.bjsoffroad.com/prod-244.htm
what is the Dog leg port compared to original?

Is this the same manifold as BJ's for $65 cheaper?
http://www.ebay.com/itm/NEW-1972-79-JEE ... _170wt_904
It says through 79 but I figured this was for emmisons stuff so if im emissions deleted then will it work?

Another ebay manifold - matches to the 1983 cherokee parts list
http://www.ebay.com/itm/258-4-2-AMC-CHR ... 956wt_1161


Pipes: Is it worth it to convert to 3" pipes.

I feel like this will help the flow...but thats only from reading other post on here. I dont actually understand how a 2.5" manifold into 3" pipe reduces the pressure if it starts at 2.5" in the first place...???

Cat:

Question is do I need it at all? Ive tried to research this answer but find 6 of 1 half a dozen of the other opinions... Florida has no emissions FYI.

I can easily replace the orginal with a 3" magnaflow "high flow" cat. Or a generic 2.5" cat. Just a matter of if it restricts enough flow to creat any negatives or if it actually messes things up with it gone.


Muffler - not trying to start a fight on which brand.. but I can get a 3" magnaflow at the same store as the Cat. So will this be a good Muffler to use with the bigger system?

The final question is...will all the "upgrades" be a waste, and should I get a stock replacement system? (I feel like the engine isnt stock anymore so that the answer is no on stock...)

Thanks and I hope Ive given enough info to help with you guys opinions ,

JP

Here is a couple photos of the current engine set up for reference. I dont have a pic of the exhaust system but if you close your eyes and think about rusty 2.5" pipe thats pretty much what it looks like. ; )

[Tin Medic]

Lose the cat, its just a draw on power. I would go with a 2.5 all the way back with a good muffler. As far as the manifold I would look at the Clifford or Borla models, a little more pricey but worth it imo.

[Florida83FSJCherokee]

Looks like I just made the cut for the Intake still fitting. 1983 and later work with the clifford exhaust manifold.

Thanks, No idea this even existed. Unfortunatly you just doubled my budget. LOL

The clifford spec is for 2.25" pipe and 3 chamber muffler. They also recommend the x pipe for another $120, plus the second muffler and pipes $$$$, but I dont know if thats necessary for my needs. Seems the dual manifolds into the y pipe, with no cat, and new muffler will be a nice upgrade in itself. Thoughts?

Borla systems didnt show anything for the cherokee but I havent looked further than there web site.

Whats the difference in running the larger pipe? Torque loss or gain? Im more about driving on road trips and around town than mudding or crawling so does that make a difference in necessary size as well?

[Stuka]

You won't lose any power with a high flow cat. Well, nothing measurable. I have 2.5" from the exhaust manifold back. Magnaflow high flow cat, and a turbo muffler.

I noticed a HUGE bump in power over the stock 1.75" exhaust. Although I already had other mods by then.


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[Tin Medic]

Are you looking at a dual or single exhaust? I ran a 2.5 single exhaust and Magnaflow muffler on my 89 GW (it has a 360) and I liked the sound and my power is fine for regular driving. The Clifford manifold would be fine as they can take the 2.25 up to a 2.5 and run that the rest of the way. The setup I am suggesting is the same that I am putting on my CJ7. You shouldnt have dual manifolds??

[Florida83FSJCherokee]

You won't lose any power with a high flow cat. Well, nothing measurable. I have 2.5" from the exhaust manifold back. Magnaflow high flow cat, and a turbo muffler.

I noticed a HUGE bump in power over the stock 1.75" exhaust. Although I already had other mods by then.
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Ok, I was hopeing you would post on this. I rememberd you saying something in a post about your set up but I couldnt remeber where... So basicly i could just change the gasket and run new pipe , high flow cat, and new muffler with the stock manifold? or did you change the manifold as well? "turbo muffler" is this a type or a brand?

Thanks

Are you looking at a dual or single exhaust? I ran a 2.5 single exhaust and Magnaflow muffler on my 89 GW (it has a 360) and I liked the sound and my power is fine for regular driving. The Clifford manifold would be fine as they can take the 2.25 up to a 2.5 and run that the rest of the way. The setup I am suggesting is the same that I am putting on my CJ7. You shouldnt have dual manifolds??

After a second look I relize that they are one piece. I thought the back half was seperate from the front and the dual openings threw me off as well... but its just a gap... are you running the 2.25'' pipe from the manifold into the Y pipe and then 2.5'' from there back?

Thanks

JP

[Locked and Loaded]

The low flow head will always be your weak spot. You can push more warter through a bigger hose. But with a small hose bib are you really doing anything?

[Tin Medic]

Yes, I am going with the Clifford manifold setup, 2.25 into 2.5 at the y-pipe.


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[Stuka]

I have the stock 80+ manifold. A turbo muffler is a type. Mine is an IMC, but Dynomax makes a great turbo muffler.

Yes the 258 head does not flow as good as a 4.0 head, but you can still pick up a good amount if power from a carb and exhaust upgrade.


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[Locked and Loaded]

.35 gap on the plugs is alittle big. You might want to come down to .050 to .055.

[carnuck]

I'm doing the 4.0L head and exhaust with a carb intake on my Eagle. I'll have to mod it for the pipe to fit past the front driveshaft but at least it's only rotational and otherwise stationary.