Before my engine build, I searched high and low for info on the 'net on how to tweak more power out of the AMC/Jeep 2.5, and just wasn't coming up with much info. I have since built the engine, and am constantly trying new things to get more power, and hopefully better fuel economy.
Here is what I have right now:
- Pretty much everything in the long block is OEM, except the cam. UPDATE: NOW RUNNING STOCK CAM
- The block was decked about 0.070" to get the squish clearance tight. I am running about 0.030" with a FelPro gasket. FYI, The Victor gasket is several thousandths thicker than the FelPro. Note: this much block-decking will require adjustment to the valve-train, as the pushrods will be a little too long. Note: the 86-up engines use a thinner head gasket, so these specs wont apply.
- The head is mildly ported. I cleaned up the casting flaws, and took alot of the valve-guide material out. I also had a local race-engine guru do some magic to the valves and valve seats.
- The pistons are OEM cast, 0.040" oversize.
-The cam is stock, but advanced 4 degrees.
- For the exhaust, I built my own shorty header, which is probably not the best choice, but better than stock. I would prefer a long-tube header, but noone makes one listed for this year or body style, and I dont know if the header listed for the newer 2.5 will fit this engine and clear all the brackets.
- For the intake, I used a long-runner intake from a mid-90's multi-port injected version of the same engine, and fabricated my own carb adapter plate. I used 2-part epoxy putty to fill the fuel injector holes.
- I am running a Weber 32/36 carb. I originally used a Weber 34/34, but was disappointed in that carb. Hard to tune, hard to find parts for, and rumored to be made by a sub-par manufacturer with the Weber name slapped on it. I fabricated my own air filter holder and use a 9" round paper filter (available on the shelf at most parts stores).
- The ignition system consists of stock components and a Summit digital ignition box. The box really didn't give any more noticeable power, but gave a much-needed rev limiter. FYI, for the inline-6 guys: the 4-banger distributor weights and springs are very different than the ones in the 6. I found alot more power running the 4cyl weights and springs over the 6cyl ones (the wights and springs are different, and the total timing for the 6cyl is dramatically more limited). May be worth a try to see if they work better for the 6 also.
In my quest for more power, I will be running experiments with the cam timing and port profile. Once I get the cam degreed in, I will be putting the Jeep on the dyno to set a baseline. I will then be re-profiling the ports and running it on the dyno again to see just how horrible the stock ports are.
Like you've never heard that before. As far as porting the heads. . .excuse my ignorance in that matter, I was just going by what a guy at Clifford told me. Of course, they wanted me to buy their race head off the shelf. . .I wouldn't worry about their website. I would call them. Those guys know more about AMC inline motors than the AMC engineers did.
