Jeep exhaust Manifolds instead of headers, are these the large opening manifolds?

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roadrunninMark

roadrunninMark

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I searched the site looking for the answer as I know I read it a long time ago but couldn't find. I am wanting to run manifolds instead of headers for a modified 318 (less than 400hp) for a mostly street car. I didn't want to lose low end power or deal with any header issues. My friend grabbed a pair of Jeep manifolds, part numbers: 53008378 and 53009377. I wanted to confirm that those are the manifolds that have the larger diameter (like the Dakota RT) than the ones on the trucks and cars. Thanks
 
53009376 is passengers side large outlet
find a drivers side 340 those are large outlet not just the 68 to 70

IMG_20220715_195818528.jpg
 
IIIRC, the 2 1/8 mag manifolds we're on on 92-3 ? Dakota RT 360 mangum only
They were only 3 or 4 more hp than std ones on the Dyno
The difference between 340 and stock was 7 hp
 
Brooks James said:
IIIRC, the 2 1/8 mag manifolds we're on on 92-3 ? Dakota RT 360 mangum only
They were only 3 or 4 more hp than std ones on the Dyno
The difference between 340 and stock was 7 hp
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I have a drivers side '93 Manifold that I couldn't use because I have PS. I went with the 340HP on the drivers side and the '93 Magnum on the passenger. and yes the openings on the Magnums are 2 1/8" and the 340's are 2 1/4". I opened the Passenger side up a bit to come close to matching the 340.
 
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Tsully said:
I have a drivers side '93 Manifold that I couldn't use because I have PS. I went with the 340HP on the drivers side and the '93 Magnum on the passenger. and yes the openings on the Magnums are 2 1/8" and the 340's are 2 1/14". I opened the Passenger side up a bit to come close to matching the 340.
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Thats the exact setup I had on my 70 Dart. I broke down and bought Dougs D453's, I wanted the extra 20 hp
 
Long tubes add low end power.

Shorty's are basically worthless.

The power difference between the larger and smaller diameter manifolds is very small.
 
Manifolds lose power everywhere compared to long tube headers but the difference isn't as much with a small cam. I have Hedman tight tubes on my Duster which fit great themselves but the outlet location sucks for routing the head pipes, bought a set of Doug's D-453 about a year ago to replace them but haven't gotten around to it. To make the exhaust not go under the steering linkage I had to use angled collectors and fab head pipes from 2 1/4" mandrel-bent "donuts". It works but I'll probably pick up 30 hp and torque everywhere with the Doug's.
 
MopaR&D said:
Manifolds lose power everywhere compared to long tube headers but the difference isn't as much with a small cam. I have Hedman tight tubes on my Duster which fit great themselves but the outlet location sucks for routing the head pipes, bought a set of Doug's D-453 about a year ago to replace them but haven't gotten around to it. To make the exhaust not go under the steering linkage I had to use angled collectors and fab head pipes from 2 1/4" mandrel-bent "donuts". It works but I'll probably pick up 30 hp and torque everywhere with the Doug's.
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I don't think you'll pick up 30hp across the board but I do think you are generally correct. And I bet you do pick up nearly that in at least part of the power range. Most old school manifolds are pretty awful at power delivery.
 
Mean416 said:
I don't think you'll pick up 30hp across the board but I do think you are generally correct. And I bet you do pick up nearly that in at least part of the power range. Most old school manifolds are pretty awful at power delivery.
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Right I didn't word that great, more like 20-30 lb-ft across the board and 30hp PEAK gain. It seems to run out of breath somewhat around 5800 RPM. I have the shorty headers currently and not only are those mediocre at best themselves but I feel like the tiny 2 1/4" head pipes that snake super tightly up over the steering linkage then back down are creating a good bit of restriction. Engine is a stock 5.9L Magnum short block with custom-grind Racer Brown hyd roller cam around 222° @ .050" intake and 224° exhaust, 110 LSA, IIRC. And has heavily ported Edelbrock heads with port-matched RPM intake and 750cfm Street Demon carb. I think it *should* pull to at least 6k with the whole combo matched correctly.
 
One other thing to note with long-tube headers is the secondary tuned length is very important... you want to keep the same pipe diameter as the header collectors as far back as possible, necking it down right after the collectors kills a good bit of torque below peak. This also applies to manifolds, you want the same pipe diameter after the outlets for at least a few feet to keep the velocity up. Bolting 2 1/2" pipes to manifolds with 2 1/8" outlets will take away torque.

This is another thing I think will pick up power for my combo, planning to run 3" pipes off the collectors at least 40" back before a crossover, if I run one at all... if I do it'll be H-pipe. Has X-pipe now and I don't like the sound. Also will likely keep it 3" all the way to the mufflers.

Sorry for rambling about my own stuff lol not trying to hijack the thread.
 
Sounds like I will just get a set of long tube headers then. For a street car, I want the low end power and don't need the high end.
 
roadrunninMark said:
Sounds like I will just get a set of long tube headers then. For a street car, I want the low end power and don't need the high end.
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Just depends on what you are willing to deal with. Everything has tradeoffs. Long tubes can be a huge pita. For a street car I strongly recommend these:

Summit Racing SUM-672330 Summit Racing™ Ball Flange Kits | Summit Racing

Also I only use Percy's seal 4 good gaskets. However it appears patriot now owns these. Anyhow I swear by these.

CHRYSLER Patriot Exhaust 66037 Patriot Seal-4-Good Header Gaskets | Summit Racing
 
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