AMC 360 poor fuel mileage

[FrankNB]

I'm just curious and kind of alarmed at how my Jeep drinks gas. I calculated as low as 5mpg (roughly) on the highway(no OD). Well, basically I have the big tank on a 94 YJ(Wrangler in the US). With bumpers, rock rails, winch, T18a, Dana20 twinned with Teralow, 60 front locked, 8.8 rear with ARB and 3 gal onboard air, 4.56 gears and 5 x 37 inch Interco SSR on Allied steel beadlocks. Bla bla bla.. My point for this showing off is an all out description is that the thing is much heavier than a stock jeep for example.

I rebuilt the 360 about 5 years ago with the Edelbrock intake, TFI upgraded distributer, MSD Offroad box, Summit cam shaft, and turned around Rochester 4bb Q-jet.

What else can I say, I easily overheat. The Q-jet is an 81 model with no electronics (and now manual choke), but designed for EGR which I don't use since my manifold is the non-egr. I have and oxygen sensor and a stoich gauge on the dash and it gives me a lean reading. I haven't tried another gauge or sensor. I've enriched the carb about 10% by switching jets or rods, I forget but I wrote it down somewhere. I have a bigass 4 core rad, an electric fan set as a pusher. Its fine driving at cruise, it's just at low speeds and high rpm that the heat gets harder to manage.

Anyway, my buddy saw that article in the offroad magazine about the Howell unit. He's been kinda hinting me to get it. In the article, you know which one it's in here somewhere, they improved the power and torque a bit but almost double their MPG. And at the same time probably cure any potential problem that my damned egr carb might be causing.

Is that science fiction and should just keep the Q-jet? Here, in Canada with the exchange and all the Howell will cost me 2000$. I don't want to invest that much if I'm not going to recover it in fuel use.

Besides that, it runs alright. Anyway, the baby started crying so gotta to.

[ironman_gq]

you could go to the junkyard and build your own efi system. as for cooling get rid of the pusher fan and either use a mechanical with a good shroud or go get a ford taurus fan, extend the shroud to cover the whole rad surface and use it as a puller on high speed.

[FrankNB]

Problem is, we put the fan as a pusher because the rad is too close to the engine so I got this Zirgo 2700 fan reversed for pushing.

Hmm.. I wish I could fit a Taurus fan in there... Something to ponder.

Just for fun, here's the build that we did.

http://entertainment.webshots.com/album/563027368YgLCqG

[tufcj]

My CJ is set up similarly. I run a 360, T-18, Dana 300, thru Dana 44s with 4.27 gears (4.88s coming) and 37" tires on beadlocks.

The 360 is a stock 74 bottom end with 1970 291C heads, a mild cam, stock exhaust manifolds, performer intake, and Howell EFI. I run a 2 core aluminum radiator with a stock fan and shroud. I don't have any problem with overheating. I get about 10 MPG average. I got 9-10 with a well dialed Holley.

You have to remember that driving a Jeep down the road is like pushing a sheet of plywood thru a windstorm, it's just not aerodynamic.

Where is your sensor installed? It is just an O2 sensor, so it should be within 12" of the head to get hot enough to get a true reading. Also, is the smog pump gone? It pushes a large volume of air into the exhaust, and will corrupt O2 sensor data.

I like the Howell, but I don't think it will cure your problems. Check and double check your timing and advance curve. If the cam has been changed, are you sure of the cam timing and the condition of the timing set?

Bob
tufcj

[FrankNB]

Well the O2 sensor is directly below the flange as you can see in this picture.

http://entertainment.webshots.com/photo/2502638740102229463aACrFC

[ironman_gq]

do you have 3.5-4 inches between the rad and the water pump pulley? with the taurus fan if you push it all the way to the passenger side and use the holes in the fan shroud to mount it to the rad mounts then the back of the fan motor clears the water pump pulley to the side if you center it the motor hits the pulley. At least thats how it worked on my CJ but I dont think the YJ's are too much different

[FrankNB]

Well, the main problem is that when we put the motor in we put it ahead just a bit too much. My option would be to see if I put a skinnier rad and a pulling fan instead. The Taurus fan would be great.

I'll really see this summer how it performs.