Headers vs manifolds?

[SlantSixSullivan]

I am building a mild 360 for my Diplomat, and I am using the slant six K member and using Schumacher mounts to do the swap. Something I want to take into account for the swap is clearance. I want to run headers instead of manifolds, but I am slightly worried about them clearing my steering box, as well as my starter. I have the high mount starter (80% above oil pan rail). Speaking of the oil pan... does it need to be changed if I'm using my slant six K member? Back to headers. For a sure fit, I could use block huggers, the real short headers. I'd prefer to use long tubes, but I might not be able to make them clear without bashing them with a hammer. My question is this: Has anyone ever used the short headers? Are they any better or any worse than long tubes or about the same?

 

[slant6billy]

Good questions. So lets revisit some things. The K member is fine from the slant. Your 360 needs a mid sump car pan. If it is the LA 360, that's easy. The Magnum 360s from the 90s require a different pan, since they were only found in trucks and have a rear sump. Headers: Some are better than others. Doug's headers being one of the best. Ram-horn style for a mid 90s truck will hit on the passenger frame rail and would not fit no matter what you do. Non- ram horn style shortie headers may work, but go up in price. If you find a set of uncracked magnum exhaust manifolds from 93-02, you get good flow and heat transfer. Infact if you can get a manifold for the passenger side from a 1993-98 Jeep grand Cherokee and the driverside from a ram, you get some nice outlet geography. What I mean is the out let dumps away from the oil pan. Factory ram truck manifolds on the pass side banks toward the engine at the outlet. On jeeps the starter is on the pass side and banks away. The idea is you want them to bank away to clear the trans (727) and linkage...etc. Plus you can get these for cheap.

 

[SlantSixSullivan]

Good questions. So lets revisit some things. The K member is fine from the slant. Your 360 needs a mid sump car pan. If it is the LA 360, that's easy. The Magnum 360s from the 90s require a different pan, since they were only found in trucks and have a rear sump. Headers: Some are better than others. Doug's headers being one of the best. Ram-horn style for a mid 90s truck will hit on the passenger frame rail and would not fit no matter what you do. Non- ram horn style shortie headers may work, but go up in price. If you find a set of uncracked magnum exhaust manifolds from 93-02, you get good flow and heat transfer. Infact if you can get a manifold for the passenger side from a 1993-98 Jeep grand Cherokee and the driverside from a ram, you get some nice outlet geography. What I mean is the out let dumps away from the oil pan. Factory ram truck manifolds on the pass side banks toward the engine at the outlet. On jeeps the starter is on the pass side and banks away. The idea is you want them to bank away to clear the trans (727) and linkage...etc. Plus you can get these for cheap.

I've heard before that Magnum manifolds flow really well. Those should be easy to find. I was shopping online for some short headers for a good fit, and found these Fit Chrysler Mopar Small Block 5.2L/5.9L Stainless Steel Header Manifold Exhaust | eBay I'm skeptical, as I'd never heard of this brand of headers before. Also, the price doesn't seem "right" to me. I don't know, though. The 360 is an LA, and may already have the correct pan. I will have to inspect it more closely. Are the manifolds for the Jeep 318 the same as the ones for a 360 Ram? I doubt it, but there are more 318 Jeeps around here than 360 Jeeps. I will do some thinking

 

[BudW]

More air flow = more power.

That said, for many headers are a pain to install, leak often, causes other problems (starter clearance, spark plug removal, and so forth), they dent easy, rust easy, and so on.

For a well performing 360, magnum exhaust manifolds (from Grand Cherokee, not a pickup) may do you fine and will be quieter.
Grand Cherokee manifolds dump between the two rear cylinders. The truck manifolds dump behind the rear most cylinder which interferes with the firewall (both want to occupy the same space).

I don’t know what years are, but the first one or two year Cherokee manifolds flow better than later year ones do.
Once I get home and (after I remember to) look up the part numbers for you to look for).

 

[SlantSixSullivan]

More air flow = more power.

That said, for many headers are a pain to install, leak often, causes other problems (starter clearance, spark plug removal, and so forth), they dent easy, rust easy, and so on.

For a well performing 360, magnum exhaust manifolds (from Grand Cherokee, not a pickup) may do you fine and will be quieter.
Grand Cherokee manifolds dump between the two rear cylinders. The truck manifolds dump behind the rear most cylinder which interferes with the firewall (both want to occupy the same space).

I don’t know what years are, but the first one or two year Cherokee manifolds flow better than later year ones do.
Once I get home and (after I remember to) look up the part numbers for you to look for).

Luckily I work at an auto parts store, so I have access to these manifolds from Dorman (at a discount, too!). I just need to know what exactly to look for. Thanks!

 

[AJ/FormS]

Long tubes should help pick up the low-rpm torque, especially with a properly placed x-over. This is important with heavy cars, low-stall TCs,and hi-way gearing.
The increased torque will find it's way back into your wallet by increasing fuel economy in steady state cruising.
But yeah, the header merge area tends to accumulate moisture and debris and in about 4 winters my un-coated TTI merges became perforated. Then I got to remove them and repair the damage.TTIs are pretty thick and the repair work went well.
The thing about headers is the merge area is possibly the only area that makes trouble. The rest of it (TTIs I'm thinking),can last for decades. And new replacement merges are available at reasonable cost. My TTIs are 15 years old, have over 125,000 miles on, and the merge area has needed attention twice, and is currently leaking again. It is finally time,I think, for new slip-on merges.
As to the x-over, I really noticed the low-rpm torque loss when I removed mine.

 

[BudW]

Luckily I work at an auto parts store, so I have access to these manifolds from Dorman (at a discount, too!). I just need to know what exactly to look for. Thanks!

I found some information on the Magnum exhaust manifolds.

'92-93 (94?) have 2-1/8” outlets. All of the newer ones have 1-7/8” outlets.

The good Pickup/Dakota manifolds are part number 53006617 (Left) and 53006618 (Right).
These exit behind the last cylinder and I “believe” these want to take the same real estate as the firewall. That said, the do appear to fit some A-bodies with a bit of modification.

Grand Cherokee manifolds exit between the last two cylinders and “should” fit our cars.
I have a part # 53009477 (Left) from ’94 Grand Cherokee that has a 2-1/8” outlet – which I got off of eBay for $13.75, four years ago.
I also have an 68-70 right side 340 manifold that I’ve had for over 30 years (actually I have both sides) that I thought about using (Right 340 and Left Grand Cherokee) – but hadn’t installed, yet.

I recorded part numbers for the Magnums - but can’t find my notes anywhere (from one of several hard drive crashes?).

Hope this helps
BudW