YES 5.9 Magnum manifolds work in early A bodies. Here is exactly how!
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Treblig
Well-Known Member
The large hole manifolds that I am talking about are the 96/97/98 Jeep Grand Cherokee (JGC) manifolds. The have a 2 1/8" exit hole, compared to the small hole magnum manifold that has a 1 5/8 or 1 7/8 exit hole. To compare, the 340 manifolds are 2 3/16", which is 1/16" larger than the JGC manifold. There are some 92/93 manifolds that are also large hole but they are designed differently. Unfortunately the JGC driver's manifold will not work on an A body BUT....the passenger's side fits like a glove and can be machined out (ported) to the same size as the 340 manifold. If you can find a driver's 340 manifold you can easily find a JGC manifold for 30/40 bucks!!!
What keeps the JGC drivers side manifold from fitting?
Dartfreak75
Restore it, Dont part it!
That's is cool what about later a bodies wonder how they would fit in them?
I’d imagine they’d fit better since the engine bays are bigger.
Dartfreak75
Restore it, Dont part it!
Yea that's what I was thinking too I have a set off a ram I may try it for kicks and giggles. I'm kinda second guessing headers anyway
Yeah I’m investigating my options as well. I currently have cheap headers on my car that scrape from time to time and when I install my HDK suspension I’ll be dropping the car even lower. So instead of coughing up money for Doug’s or TTI’s, I’m thinking of going with manifolds or buying a set of $75 ram shorty headers on eBay and seeing if I can make them work.
Treblig
Well-Known Member
The JGC is a Mopar but it has a newer Jeep engine. The Jeep engine was designed with its' starter on the passenger's side. Our Mopars have the starter on the driver's side. The Jeep, with its' starter on the passenger's side, has a ton of room in the space that our Mopars have a starter. With all this extra space where our starters normally live the Jeep engineers decided to use this space for the manifold to be. As a result the Jeep driver's manifold exits where our cars have a starter. I only know this fact because I attempted, for many many hours, to install a JGC driver's manifold in my 69 Barracuda. The Jeep manifold ran right into the Barracuda starter no matter what I tried ( I also had installed the smaller later starter to increase the space in that area). If you install a Jeep motor (318 or 360) in your Mopar you could probably use the Jeep driver's manifold. You're welcome to try this for yourself but with our Mopar starter on the driver's side I don't see any way it can be done. If it could be done someone would have already done it!! On the other hand (right hand...LOL) the JGC passenger's side manifold fits like glove on our Mopars and offers much better flow. So if you can find/get a 340 driver's manifold it's a piece of cake since the JGC manifolds normally sell for $25-$40 at most car salvage yards!!!
Dartfreak75
Restore it, Dont part it!
I have two sets of 360 manifolds one off a magnum truck the other is off a 77 charger I think they where f bodies maybe? I'm not sure. I may do some testing and see what will fit. I like the performance side if headers but prefer the original look of manifolds. And there is the ground clearing issue and rusting out and pita to change plugs etc! Lol
Bulldozer
free ice cream sandwiches
does the engine sit crooked with the shims only on one side?
Thanks for the explanation! I’d completely forgot about the fact that the Jeeps have the starter on the “wrong” side.
Treblig
Well-Known Member
Those will probably not have the large 2 1/8" exit hole like the JGC manifolds. Check and see....let us know??
Treblig
Well-Known Member
FYI..........that manifold test did not try the JGC manifolds, especially the ones that I machined out to the same size (or larger) than the 340 manifolds!!
Yeah I really wish they would’ve tested magnum manifolds
Dartfreak75
Restore it, Dont part it!
That is interesting. I cant believe the 360 manifolds performed so close eith the 340s
Dartfreak75
Restore it, Dont part it!
Ok I will look at them and get back to you
Treblig
Well-Known Member
Remember that the magnum engine (as it's known) was made for many years AND all or most of the manifolds on these magnum engines were referred to as "magnum" manifolds. BUT.......... as it turns out, most of these "magnum" manifolds were NOT the large hole (2 1/8") manifolds. There were some large hole manifolds made in 92/93 (Dakota manifolds I think) and some made that came on trucks and vans in different years. I researched these manifolds for many years. I purchased many, many so called "magnum" manifolds and conducted many experiments. At one time I had as many as 30 sets of manifolds.
I measured all of them and test fitted many of them on our Mopar engines. Some of the large hole truck/van manifolds will work on the passenger's side but exit very close to the firewall and will introduce "heat" into the firewall. I found that the JGC manifold (96/97/98) fits perfect, even better than an original 318 manifold. Just remember that just because a manifold came off a magnum engine it doesn't mean that it has the 2 1/8" exit hole.
Dartfreak75
Restore it, Dont part it!
I'm going to try this In my 75 dart. What down pipes are you using? Did you have to make them or will any abody down pipe fit? Sorry if this had already been covered.
Treblig
Well-Known Member
This was custom made while the engine and the 340 exhaust manifold was installed on the driver's side. I used a section of mandrel bent J pipe but it's actually better to use a mandrel bent 2 1/4" donut. The passenger's side (JGC) is a piece of cake for anyone. This was in a '69 Barracuda (318).
Dartfreak75
Restore it, Dont part it!
Thanks that is awesome. What flange did you use for that? So you welded the flange on the prebent tubing?
Treblig
Well-Known Member
Yes, that's the only way it can be done if you want mandrel bent pipe. Walker sells the flat flange on ebay. The donut can also be found on ebay. You have to weld the mandrel bent pipe to the flat flared end with the flange in place. Most muffler shop can put a flat flare on some 2 1/4" pipe.
Dartfreak75
Restore it, Dont part it!
Thanks man that is awesome that gives me all kinds of ideas and options!
Treblig
Well-Known Member
You're welcome. Although I figured out a way to make the downpipe on the bench, the easiest way to do it is to install the manifold in your car and piece it together under the car so that it clears everything and fits well. You can tack weld the pieces in place and when you have it exactly in the right place (orientation) you can remove it and weld it up 100 percent. This way it fits your set up perfectly.
Dartfreak75
Restore it, Dont part it!
Yea that is what I was thinking too. Kinda from it up in the car then take it back out and weld it up and reinstall it.
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