Jetting ? on 1987 2.4 Merc

[honedout]

Have a stock 87 2.4. Stock air box. Someone has cut a homemade exhaust relief at the bottom of the mid section on both sides. Will jetting need to be changed or stock ok. Runnin 74 mains now.

[hydroholic]

No, you should be ok with the jetting you have now.It's most important when you change the air and fuel flow into the motor. For example when removing the air box and installing velocity stacks which will allow the air in theory to enter through the carbs and intake at a smoother and slightly faster rate than compared to what it was entering before.But you will still have the same amount of fuel entering as before which leads to a lean mixture. If this mixture is lean enough thats when you can have some big problems like melting some pistons or worse. And even more importantly any time you raise compression you will need to rejet . The cut outs will allow the exhaust to flow out faster because of less back pressure due to them being above water at throttle.This in turn will allow the fuel and air mixture to enter the cylinders faster. But the ratio of fuel to air should stay the same, just enter faster and after it has burned, exit faster. Now I hope I have not opened up to big of a can of worms as I am sure someone will disagree with me. Not saying I am 100% right but this is my experience and have always done this on all my motas (2.0's 2.4's and 2.5's and my current 2.4 200) and it didn't affect them. But it's real easy to run it,switch it off, and take a plug reading. Then you will know for sure. Even though so far it has never affected any of mine, every new motor ( new to me) I relieve the exhaust on, I take a plug reading just to be sure. Better safe than sorry! Good luck.