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Unread 04-30-2013, 03:56 PM   #16
Alex77cj7
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Unread 04-30-2013, 04:12 PM   #17
pman
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Quote:
Originally Posted by ADDZ71 View Post
pman,

Are those manifolds off your CJ? The reason I ask is the driver's side manifold is a rear dump which if I understand correctly will not work in a CJ due to interference with the clutch linkage. The CJ's had a special Driver side dump that is in the center of the bank. Look at Matt's thread on this and you will see the difference.
Funny you spotted that (Good eye); I noticed it when looking at Matt's thread a while back. No telling what the PO did on this 304, but these mani's were on the CJ. It did clear the linkage, but was a tight fit. I may have a stray picture laying around when I had the fenders off that showed the setup. Crap; if it doesn't work with the new pipes, I may be calling Summit!
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Unread 04-30-2013, 04:50 PM   #18
Matt1981CJ7
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The driver's side center-dump, on the bottom of my pic below, is the CJ version.

Mine came from an AMX Javlin with a 401.

Matt
exhaustmanifolds6.jpg  
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Unread 04-30-2013, 05:23 PM   #19
rah2eq
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Just to chip in: my CJ came with headers. It was a huge pain to get them to stop leaking. They were pretty warped but I ended up using two gaskets on the driver's side to get through inspection... As far as I know they are Hedman inframe headers, and other than the initial leak problems they've been fine. I welded on some thrush mufflers and put them out the back and it has been smooth sailing. I haven't had any access issues to anything (and I've had to get to a lot) and they haven't caused any other problems. I've never had a CJ with manifolds so I can't speak to any sort of power difference or change.
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Unread 04-30-2013, 05:28 PM   #20
Matt1981CJ7
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Keith,

FWIW, if you search around muscle car forums, most of the AMC guys say you will gain next to nothing, performance-wise, by putting headers on a stock 304. The consensus is, they aren't worth the trouble, unless your engine is highly modified.

Personally, I also think most headers put the exhaust pipes and mufflers in a very vulnerable position on a CJ, especially if you do any wheeling at all. If your rig is just a mall crawler, then it doesn't matter.

Matt
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Unread 04-30-2013, 05:41 PM   #21
pman
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Matt, you just wanted to show off those "purdy" pipes again, didn't you?

I called my muffler guy today and told him about the "potential" problem he may run into with the rear dump. He's a motor builder and long time Jeep owner. His words: "I'd rather get creative and design the exhaust to work with your current manifold setup, rather than put headers on it; the minimal performance gains on these motors aren't worth the potential headaches with leaks. If it was a street car, we'd be having a different conversation".

Definitely not trying to "stir the pot", but wanted to pass along the words of someone who does this for a living.

P.S.- I am not "anti-headers" by any stretch. I'm just not willing to part with my cash if the benefits aren't significant over stock. If you gave me a pair of those Doug Thorleys in the pic on this thread, I'd install 'em ASAP!!! Sorry for the slight derail, Keith!
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Unread 04-30-2013, 06:00 PM   #22
Matt1981CJ7
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pman,

I am proud of my "purdy pipes". Thanks for the excuse.

I will add, I'm very pleased with the VHT paint I used on them. They still look exactly like that pic after 2K miles.

My exhaust guy, who specializes in 4x4s, said the same about headers, and dual exhaust, on my 360. He said the 5-10 HP difference that headers may make wasn't worth the potential hassle of using them. He said his primary concern on a 4x4 rig was to tuck the exhaust up and away from harm.

Matt
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Unread 04-30-2013, 07:22 PM   #23
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Quote:
Originally Posted by Matt1981CJ7 View Post
He said the 5-10 HP difference that headers may make wasn't worth the potential hassle of using them.

Matt
You know I love ya but there could be closer to 30 HP between a stock exhaust set-up and full-length headers with high-flow cats and good mufflers on an otherwise completely stock engine.

Believe me, I've seen my fair share of cranky exhaust guys and I shouldn't let all of this old folklore stand my neck hair up .

You're sure right about being tucked up neat and out of the way!
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Unread 04-30-2013, 07:44 PM   #24
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Quote:
Originally Posted by swatson454 View Post
You know I love ya but there could be closer to 30 HP between a stock exhaust set-up and full-length headers with high-flow cats and good mufflers on an otherwise completely stock engine.
That was my exhaust guy's off-the-cuff calculation.

I'd love to see how you arrived at yours.

Matt
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Unread 04-30-2013, 07:49 PM   #25
nshefbuch
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Quote:
Originally Posted by swatson454

You know I love ya but there could be closer to 30 HP between a stock exhaust set-up and full-length headers with high-flow cats and good mufflers on an otherwise completely stock engine.

Believe me, I've seen my fair share of cranky exhaust guys and I shouldn't let all of this old folklore stand my neck hair up .

You're sure right about being tucked up neat and out of the way!
30??? Where are you getting your numbers? This could only be true on a turbo car, diesel, or newer v8's that get a "X" pipe put in. All this and unlimited time on the dyno would be the only way you can gain 30hp from a exhaust switch.

What was said about a 5-10 Hp gain is very realistic. Truth be told you need the heads ported to match the gaskets to actually gain much. Like I mentioned a X or H or Y pipe is the big key to power gains. Mandrel bends of course are a must for a decent gain.
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Unread 04-30-2013, 07:49 PM   #26
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Quote:
Originally Posted by Matt1981CJ7 View Post
I'd love to see how you arrived at yours.

Matt
Chicken bones and entrails

You guys do whatcha want. Just make sure you have "the proper amount of backpressure"


Shawn
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Unread 04-30-2013, 10:37 PM   #27
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I would really like to see some Dyno numbers on the claimed 5 to 30 HP increase. And where it's at in the HP Torque curve. And, what happens to the torque #'s.
Remember, were talking about a 304 with a max HP of around 150 in the 70's, the numbers go down in the following years.
To me it's not worth the chance of leaks, and cutting of the inner fender. I'll stick with the cast manifolds.
Bill
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Unread 05-01-2013, 02:54 AM   #28
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I went w/a Pacesetter in frame set, and they presented a problem not addressed here. Since they're in frame, I needed a mini starter. A new starter was on my list anyway, but some of you might find this an unpleasant surprise. I wish I had blown the extra coin on the ceramic set. And yes, the stock 304 manis are in my loft. I had my machinist help me port match these and the heaers while it was apart. I took a ton of material off the stock ones to get them to match.
Sorta OT. But I always kinda giggle when somebody mentions science w/stock jeeps. Say to yourself "AMC/Jeep/Renault and science".... and see if you don't grin!
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Unread 05-01-2013, 04:18 AM   #29
nshefbuch
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FYI for those with warped heads/headers. Remflex makes gaskets that are collapsible. These are for any warps and seal up very nicely. Yes they are expensive but worth it to not tear it all apart and clean gasket material every year or two.
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Unread 05-01-2013, 05:53 AM   #30
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Some random thoughts from years of not only using, but working on headers as well...
Minimal HP gains under 3500RPM's
leakage
warpage
more underhood heat
louder
prone to cracking
spark plug/ starter access can be a pain

Pluses:
sound
looks
There is a gain in performance in the upper RPM ranges, especially when coupled with other engine mods
can be cheaper than a new full system (fender well headers)

Personally, I prefer stock manifolds with either a dual system or a larger (up to 3") single, coupled to a free flowing muffler(or glass pack if you like more sound), plumbed out the back. I like to have a compression flange installed by the transmission, allowing the pipe to be broken for easier access in case the trans needs to be dropped (not necessary, but it usually helps). These systems are solid, long lasting, and pretty much maintenance free.
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