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AMC 360 rebuild

5K views 6 replies 6 participants last post by  monzter 
#1 ·
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.
 
#4 ·
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.
how is that 3900 lbs??
my long box 71 c-10 is that and much longer and wider than that jeep
 
#5 ·
Yes, Jeeps are "heavy"...


The 360 is capable of nice low-end power. A "torque" cam, something like a Comp High Energy grind would be good. Keep duration around 206-210 @ .050 on the intake. Lower lift is also desired (under .470").

A good "comp" valve grind will also help a lot.

Getting it to idle down that far is going to be a trick, and can adversely affect oil pressure.

On that, AMC engines are notorious for wearing out the oil pump, integral with the timing cover. New units ARE available, but not cheap. '73-newer is "different" from the early ones. If the housing shows more than .005" wear between the wall and the gear, it's gotta go. Leaking water is a concern, but I've seen many more with bad oil pumps than corrrosion problems.

Once properly done, the AMC V8 is a GREAT engine, long-lifed and powerful.

Jim
 
#6 ·
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).

Here 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.
 
#7 ·
Thank you all for your help. Would it be possible to build a engine that would be close to 300 Horsepower while meeting all my goal's maybe except for the idle speed. since it might hurt the engine in the long run.
I have been reading online, I can get a GM HEI distributor for my AMC engine, wouldn't that be a good choice ?
Is there any particular camshaft you would recommend above others ?

Here's a photo of this Jeep.. Weight is a rough guess, At least I prefer to say that the weigh't is more on the heavier side than not.

Regards.

 
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