what headers fit and gas mileage questions

ArtD · #1 07-02-2008, 11:39 AM

Hey guys, got a few questions...... first off we are talking about a 2001 2500 Maxi van with the 5.2 318 engine with 120,000 miles. I would like better fuel mileage, who wouldn't right? I'm figuring out that the Nitro "chip" I got off of Ebay is nothing but a resistor that tricks the system into richening the mixture. Which might help performance, but probably won't do anything for the MPG's. Being an old school racer, I'm thinking headers will have to help this thing breath better. Who makes headers for this van, and if there is no specific application (there appears to be none), what will actually fit? Anything out there??? Moving to other things, getting rid of the clutch fan and putting a modern electric fan system on should help as well, anyone know how much? I live in the Pacific NW, and at times will encounter hills, so should I put larger diameter tires on or not? Besides doctoring the fuel itself, are there any other fairly easy fixes? I'm going to be doing some light trailer towing, 6x12 go-kart trailer to be exact. These are very handy vans to have around, and I figure its probably easier and cheaper to try and get better mileage then to dump it and spend who knows how much on something that at best will probably get maybe 18 tops. Whats the best that I can get? What will work here that will increase mileage, won't hurt the anemic performance, (the headers and fan will help) and still be cost effective?

IGadget · #2 07-02-2008, 04:39 PM

The LA 318 that is in this will take many of the same mods that similar auto engines will see.The best thing would be to readover the 318 informaiton on allpar.com. the year of the engine determins what sort of options you have, More than likely the headers are not the problem, but the exhaust system from the manifold back. I ran seperate duals with 2" pipe instead of the shared 2.25" and picked up about 3mpg. course you cant ditch the cat like I was able to sneak on my 83. you also have either TBI or straight fuel injection, so maybe a good tune would be the next place I would hit.

I have heard of in body engine rebuilds, but I don't know at what year that became harder. The best I heard was remove the passenger seat and take the engine out that way, but I never tried it.

relayda · #3 07-05-2008, 02:14 AM

...there are less expensive mods, K&N filter, throttle spacer, under-drive pulley and a straight thru muffler. ~$200 total and can be installed in a couple of hours with hand tools. The hardest task is getting the old muffler off.

You could also install a high flow cat and at low stall speed towing/RV torque converter. ...then headers.

ArtD · #4 07-05-2008, 12:46 PM

The rest of it I get, how does a throttle spacer help out the fuel mileage? Where I live there is no emissions testing, so I could yank the cat. I am toying with the 2" exhaust with dual flowthru mufflers. Does anyone know if a flexfan is good for this application? I would think that getting rid of the clutchfan would help out. But then it is there for a reason. A modern electric fan system might be a better solution, I'm defininantly in the information gathering stage. So what headers DO fit? Nothing is listed, is there any application that fits and still allows the cover to be properly used?

IGadget · #5 07-05-2008, 05:50 PM

These people were going for horses, but helping the exhaust flow smoother will deffinately help gas mileage providing there is enough back pressure on the system.

http://moparmusclemagazine.com/techa...8_engine_build

You should clean your IAC just because it is an easy fix for idle issues, and those waste gas.
the bigest mileage differences can be had though driving habbits and a well tuned engine.
Just search on here for Stev's well written article on that.

relayda · #6 07-06-2008, 07:37 PM

...Yup, the flex fan is a great idea. I installed a fan off of a late model Mustang with a 200F-170F switch.

Throttle spacers cause air turbulance for better atomization.

Your best bet with the headers is to compare the stock manifolds with those on the trucks and Durangos. Your main concern is that they clear the suspension, body etc. They may or may not hook up to the stock pipe. ...a lil better than trial and error...

Go with a high flow cat...too low of backpressure with stock engine internals my adversely affect your bottom end torque.