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Injection pump on mechanical 350

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While I am new to the site, I was pleasantly surprised at how quickly I got some great advice and tips from fellow members on my first post.

So.... here is another question that has been on my mind.

I know that my 1990 Mack CH613 four axle tractor only has a 350 engine, but it sure seems like it should have a lil' more power than it does? I had my yearly smoke test last week and the guy told me that my engine runs extremely clean. Suggested I never get rid of this truck, very clean piece with 611,000 miles.

Is it relatively easy to turn up the injection pump on this motor to get more power out of it? I have single exhaust system that I intend on changing to dual 7inch straight stacks this spring. Truck also has a 12 speed trans that I HATE. Very difficult to shift smoothly without a lil noise between gears. (no matter who is driving). (Has the air shift selector for High/Low/neutral/reverse).

Any other suggestions for pulling more power from this little power plant? Thanks, Brian

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The Robert has a small squarish cover at the rear, usually has the jake switch attached with two bolts, fuel screws are inside. The America has a square angled cover on the top rear section of the pump, 6 bolts hold it down, one is usually covered with lead so you can't remove it(ok!). Fuel settings are under here. There should be a small tag on both pumps in the center section near the bottom I believe telling you Robert or American.

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Ok, I have the Robert Bosch pump, it has the square cover with two slotted head screws holdin the jake switch on. I took it off and looked inside and saw the two screws. One is large and one is much smaller. I assume one is for idle and the other is for fuel supply?

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