I have a dead stock 85 D100, 225 with a 4 speed OD. Anyway, the truck gets around well enough with light throttle application. I find it strange, however, that it seems to have less power when applying more throttle. Timing is right, engine seems tight. Any comments or ideas? Is it that under carburetated?

Undercarburetion would show up at the higher RPM ranges, not as much in normal acceleration.

Can you give us more information? Does it bog, then slowly pick up? Does it require feathering the throttle just to build speed?

Lots of possiblities: Bad accelerator pump, fuel restriction, bad timing advance, etc.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

...exhaust restriction (quite likely on an '85), screwed-up lean burn, dead or dying oxygen sensor and/or other feedback fuel management components if so equipped...

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Too many people who were born on third base actually believe they've hit a triple.

The truck doesn't bog like an accelerator pump issue, and basically needs to be feathered all the time. I have not power with additional throttle, and instead run the engine to a higher rpm range under light throttle to accelerate more quickly. Basically, there is no perceivable power difference between having the throttle barely cracked open to wide open. The static timing is set to stock specs. It does not have lean burn. Interestingly, it has a fairly noisty exhaust leak under the hood when cold, but after about a half mile, the engine has much more power, runs smoother, and doesn't make the exhaust leak sound anymore. I haven't had time to look into the exhaust leak in detail, but it seems to be around the cat.

Does the engine get any spark advance as the RPMs increase?
Static timing is only the first piece of the timing advance curve, there needs to be some centrifical advance and vacuum advance to get the engine to develop power at higher RPMs.
It is time to "plot" your advance curve using a timing light.
DD

The exhaust you hear leaking under the hood is getting sucked into the air cleaner via the thermostatic air cleaner. That'll put a hurt on performance, for sure. You'll definitely want to check the exhaust system for leaks and clogs. Doug's suggestion to plot the timing advance (or at least watch the timing mark with a timing light as you rev the engine) is a good one. Does your distributor have a vacuum advance pod on the side?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.