If you want a quick and simple wake up, then adjust your ignition timing. Factory setting is about 4 degrees BTDC, but you can usually go as high as 12-16 degrees without major issues. Then buy or borrow a dial back timing light and check the timing curve. You want another 18-20 degrees of timing from mechanical, preferably by about 2500 RPM. Do not exceed 36 degrees total.
Make all these checks with the vacuum advance line disconnected and plugged. Then reconnect the line and verify you get 18-20 degrees from vacuum advance. This is for cruise economy, not performance.
Bruce
Good advice, but adding anything more than 12-14 degrees vacuum advance to 36 degrees "total" advance may cause pre-ignition when lightly rolling on throttle at cruising speeds. That's because these engines were set up to run very low (even negative) initial advance, so the factory tried to get some cruising speed fuel mileage back by adding 20 to even 30 (!) degrees of vacuum advance. The fix for pre-ignition is NOT backing off initial or total advance, but to limit the amount of travel by the vacuum canister pin to around .100"-.120". I could try to explain it here, but there's lots of information already available. Just google "limit GM HEI vacuum advance". There are kits to do this, but it's easy to make your own limiting plate.
Actually, after increasing initial + mechanical advance to 36 degrees, keep that vacuum advance disconnected and plugged, and then drive around at various speeds and loads with engine up to operating temp. If all is OK, reconnect the vacuum line to the canister. If only then do you hear pinging under light loads, you know that the limiting plate is required. Whew!
As mentioned above, cap, rotor and plug wires are things to check, or even replace as preventive maintenance. Also, a free-flowing exhaust system is one of the best ways to increase power and fuel mileage. With an otherwise stock engine, your exhaust manifolds are
just fine. Full dual exhaust using at least 2-1/4" tubing and low-restriction mufflers will help a lot. Whatever mufflers you choose, they should not be "necked down" internally, for example from 2-1/4" to -1-7/8" or less. (!) This is called "restriction" which is the easiest way for muffler manufacturers to reduce noise levels. So even if you stick with stock single exhaust, look for a low restriction muffler and make sure the cat converter (if you have one) is in good condition.
Don't worry about carb and cam until you get all these things sorted out. In fact, with stock heads and tall axle ratio such as 2.56 or 2.73, a cam alone may hurt more than help.
Finally, make sure the vacuum hoses are not cracked and that they fit on the nipples snugly. Also ensure that all emission systems are working properly.
***Edit: Is this a 305? If so, what I said above about a performance cam hurting more than helping goes doubly! Many years ago I had a used 81 C10 with a 305, TH350C trans, and 2.56 axle. That was the standard ratio back then for a C10 with a 305. On a good day, that thing was a dog. A previous owner had installed a switch to enable the lock-up converter, but I rarely used it, even on the highway. Adding any more camshaft duration would have made that truck almost useless, unless I drove it around in 2nd gear most of the time.
