exhaust manifolds

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   Would anyone have any info on stock dogleg exhaust manifolds. I have 2 sets, one from my 79 AMX v8 and a set from a late model v8 out of a Cherokee. Will one flow better than the other or are they basically the same? Thanks for the help.

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79amxv8 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/04/2015 Location: Iowa Status: Offline Points: 119	Post Options Post Reply Quote 79amxv8 Report Post Thanks(0) Quote Reply Topic: exhaust manifolds Posted: Jul/31/2018 at 10:41pm
	Would anyone have any info on stock dogleg exhaust manifolds. I have 2 sets, one from my 79 AMX v8 and a set from a late model v8 out of a Cherokee. Will one flow better than the other or are they basically the same? Thanks for the help.

tufcj Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Supporter of TheAMCForum Joined: Jul/10/2007 Location: Watkins, CO Status: Offline Points: 4097	Post Options Post Reply Quote tufcj Report Post Thanks(0) Quote Reply Posted: Aug/01/2018 at 9:51am
	Flow is probably no different. If the Cherokee manifold is 1980-1991, the driver side is different from earlier manifolds, and probably won't clear clutch linkage if you have a manual trans. Bob tufcj
	69 AMX 74 Javelin AMX 67 Rogue If you need a tool and don't buy it... you'll eventually pay for it... and not have it. Henry Ford

scotty54 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Aug/07/2015 Location: TN Status: Offline Points: 70	Post Options Post Reply Quote scotty54 Report Post Thanks(0) Quote Reply Posted: Aug/29/2018 at 8:18am
	I recall an article years ago that early Jeep exhaust manifolds were better flowing. By early, I mean pre-smog pumps. Based on that I purchased an old set from a junkyard Wagoneer and am about to install them on a 77 Cherokee, eliminating the smog pump and AIR tube manifolds. Just eliminating the smog items and the tangle of vacuum lines (plus real tuning) will likely make more of a difference than the manifolds but they look nice. The actual difference, even on a dyno would be negligible I think. Headers would clearly be better.

ramblinrev Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: Dec/28/2008 Location: Wisconsin Status: Offline Points: 11543	Post Options Post Reply Quote ramblinrev Report Post Thanks(0) Quote Reply Posted: Aug/29/2018 at 8:22am
	Free flow manifolds were said, at the time, to flow almost as well as headers!
	74 Hornet Hatchback X twins (since 1977) 62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981)

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6910	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Aug/29/2018 at 10:43am
	The smog or non smog Jeep manifolds that are 2-1/4" ID were what I read the "free flows" and 15 HP better then the standard 2" and headers at the time were 30 HP gain. If you tweak the free flows by grinding off the cast flashing and port matching they were supposed to give a 20 HP gain, dual exhaust of course. This was a Jeep article years back. Don't know if the article stated this was bench tested or dyno tested. I have the 2-1/4" on my 401 and have not been disappointed for a street vehicle.

scotty54 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Aug/07/2015 Location: TN Status: Offline Points: 70	Post Options Post Reply Quote scotty54 Report Post Thanks(0) Quote Reply Posted: Aug/30/2018 at 5:52am
	That's really cool. Smoothing out cast iron runners sounds like a big job though.

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6910	Post Options Post Reply Quote Trader Report Post Thanks(1) Quote Reply Posted: Aug/30/2018 at 7:30am
	You don't have to make the ID completely smooth. The article was about removing the casting lumps, seam "lines", port matching and excess material to smooth flow at each port. With a die grinder and carbide oval burr, it took about 20 minutes per manifold. Never polished anything. Also the exhaust recommendation was 2-1/4" for a 360 and 2-1/2" for a 401. Don't remember the build specs of either or HP achieved. Wish I could find the article - 4-wheeler magazine as memory serves. Found this on another forum to put some numbers to this: http://www.ifsja.org/forums/vb/archive/index.php/t-151504.html Edited by Trader - Aug/30/2018 at 7:55am

1982AMCConcord Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/13/2012 Location: Kenosha, WI Status: Offline Points: 1287	Post Options Post Reply Quote 1982AMCConcord Report Post Thanks(0) Quote Reply Posted: Sep/02/2018 at 11:58am
	Uh... I might be wrong on the 2nd part of this... But if the set from the 79 AMX has a log style passenger side exhaust manifold... That is probably a 10hp restriction over the high flow version. Also... If the Jeep style manifold has a log style driver's side exhaust manifold... Then that won't work in the engine bay of a RWD car because it's designed to clear a front 4x4 axle of a v8 Jeep. If you use a high flow manifold on an AMC small car the strut rod bracket on the pass side need to be ground down and the collar on the manifold needs to be clearanced. To my knowledge... High flows fit all large cars. Edited by 1982AMCConcord - Sep/02/2018 at 12:01pm

Boris Badanov Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4210	Post Options Post Reply Quote Boris Badanov Report Post Thanks(0) Quote Reply Posted: Sep/02/2018 at 12:07pm
	In general port matching or making sure the steps in the transition are not impeding flow will make small gains, but not much. IMO blend the manifold opening to be a match or a little (very little) bigger than the head and don't mess with the head port. Clean up any heavy sl*g but do not re-shape (unless you have access to a Flow Bench). The flow exiting an exhaust port is no longer air, and it exits at super sonic speeds with a shock wave. A Flow Bench can help a little but I am of the opinion that the engineers at AMC did a fine job so for the most part, leave it alone or go with headers.
	Gremlin Dreams

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6910	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Sep/02/2018 at 12:48pm
	This older post has pictures of the manifolds and some discussion: http://theamcforum.com/forum/best-exhaust-manifolds_topic42669_page1.html I used the 159/160 on the 69 Javelin with 2-1/2" exhaust with no clearance issues either side.