Originally Posted by monzter
I have this engine in an old Jeep CJ7 that is used for off roading, mostly in snow. I plan on a total rebuild on the engine, since it's worn and doesn't have much oil pressure or power. What I'm aiming for is power from Idle - 5000 rpm's and I would like it to idle at 500 rpm's if possible. It must be reliable and gas mileage is a concern for me. Here's a rundown of things I have now and the Jeep itself.
AMC 360 engine with Edelbrock Performer intake, Holley 600 cfm 4 barrel vacuum carburetor. 1.5/8" Long Tube headers with dual 2.1/2" exhaust. Everything else is stock as far as i know. T-18 4 speed transmission with granny low 1st gear, and Dana 20 transfer case. gear ratio is 4.10's and the Jeep is on 36" tires. It weight's around 4500 lbs ready for trip, with gasoline, luggage and everything that's needed for 2 day trip in the mountain's. It's 3900 lbs empty.
I wouldn't worry too much about it idling at 500 rpm- let it idle where ever it needs to, to transition smoothly from idle into the transition/main carb circuits. Most cams in the range you're looking at will idle smoothly in the 700 rpm range, give or take. Idling too
low can hurt the main bearings and can even cause transient pinging; you'd be better off avoiding those things altogether.
You will do fine w/the Performer and 600 cfm carb along w/an "RV" type cam like Mr. P-Body has recommended. That will give good low end torque and potentially
better mileage than a hotter cam. Be sure the compression ratio isn't too high- using a mild cam means less static compression is needed. You can look over the cam manufacturer's sites for recommendations on CR for their various cams. Some general guidelines/recommendations are here
AMC heads actually flow pretty darned good- and cylinder head flow is key to making good power. A 3-angle valve job along w/the 1-5/8" headers you have will work good. Feeding the engine cool air always helps; use a free-flowing air filter as well as good fuel filter(s).
One of the most important things to take care of is setting up the advance curve in the distributor. Using more than the stock-specified amount of initial ignition lead will almost always help performance by smoothing the transition from idle to higher rpm. Total timing has to be kept below the area where detonation can occur, and the rate of increase in the timing must also be kept below the threshold of detonation. The reward for getting this right is a much
better performing vehicle- including better mileage than the stock specs will allow. Some info on timing is here
(the page was originally on the GM HEI but the timing info is basically universal once the initial and max timing amounts for the AMC is substituted).
is some assorted AMC info. Also, looking at some of the calculators
from Wallace Racing, you'll see the 4.10 gears w/36" tires is about equal to 3.42 gears w/30" tires, so you should be good to go as far as the rear ratio goes. That said, getting good mileage (relatively speaking) is going to be dependent on the roads (hills/grades, etc.) as well as your right foot.