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I don't have plans or this right now because I just replaced one exhaust manifold but....how much better are headers vrs truck manifolds both through dual exhaust? The engine is a stock 400, 600 cfm 4 barrel Holly, auto, an my only concerns are torgue, mileage, noise, then HP. Rarely get into the 4000 and above revs, 70 % city, 28 % highway, 2 % offroad. So are the truck (fat Rams horn sorta) manifolds that bad?
 

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For what you are using your truck for, the manifolds are fine. You will eventually have to replace the headers if you put them on but the manifolds will last for a very long time.
Only time I see a concern with manifolds is if they are cracked or missing.
 

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If you buy good quality headers, they too will last a very long time. My hot-coated tri-y headers (I forget the manufacturer) are 12 years old, and not rusted at all...

Headers make a BIG difference in the way the engine runs...

Best bang for the buck in my opinion....

Mike
 

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If you get crap headers and jet hot them they will last and not disintergrate, would you rather breath out through a straw or 1 inch pipe
 

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True enough, but to predict what primary size will be best for a specific motor, you must know where you want the engine to develop peak torque. If the existing torque peak is at bit lower RPM than you prefer (typical in under-cammed or stock motors), it can be "bumped" a bit by increasing the primary diameter. If the torque peak is too high (motor is "peaky", with no range and poor recovery from gear changes), the peak can be adjusted down by using a smaller pipe. A change of 1/8" in the primary diameter will raise or lower the peak torque RPM by 500 or so.
 

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OhPinions said:
True enough, but to predict what primary size will be best for a specific motor, you must know where you want the engine to develop peak torque. If the existing torque peak is at bit lower RPM than you prefer (typical in under-cammed or stock motors), it can be "bumped" a bit by increasing the primary diameter. If the torque peak is too high (motor is "peaky", with no range and poor recovery from gear changes), the peak can be adjusted down by using a smaller pipe. A change of 1/8" in the primary diameter will raise or lower the peak torque RPM by 500 or so.
Yeah i was reffering to small primary tubes not 2 1/8 or 2 1/4 more like 1 5/8
 

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No slam intended ED_3 ;)and that's a good size you listed.
 

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I recommend 1 3/4" or 1 7/8" primary tubes for a big block... 1 5/8" is just a little too small...

Also Tri-Y designs have lower torque peaks that equal length (racing) headers do. The Tri-Y's scavenge very well because the cylinders tied together draw off of each other...

Mike
 

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I run hooker Comps on my 440. I had Headman. The Headman I would rate a 4 on a scale of 1-10. The Hookers, 9. The Headman leaked so much at the flange, I was constantly hearing pip pip pip... I was constantly changing flange gaskets. I am on one set of gaskets with the Hooker. Thicker flange? Higher quality steel? It is the old story, spend a little more now or ....... Definitely recommend Headers.
 
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