You can gain a lot of flow...
You can gain a lot of flow with a simple pocket port. The valveguides are narrowed into an upside-down cone. This is easy to do with a little patience and really improves flow in an area of the head that is typically the biggest restriction.
You can check your alternator's performance. It should be putting out around 13.5 volts. All you have to do is ground one of the leads and then hold the other one to your alternator output. You have to rev up the engine a little because the alternator won't start putting out peak power until around 3,000 rpm. If you aren't getting around 13.5 volts, you probably need to replace the alternator.
Bigger Pushrods Weight is normally the enemy in the valvetrain, but not when it comes to pushrods. With the high-spring pressures and tall rocker ratios common in today's racing engines, pushrod flex is becoming an increasingly common problem that is often difficult to identify. A flexing pushrod causes the valve to open later than it should, and then springs back into shape and flings the valve so that it doesn't properly follow the backside of the cam and slams shut. It often gets confused for springs that are too light.
The solution is to swap the standard 51/416-inch pushrods with beefier 31/48- or even 71/416-inch units. Dual taper pushrods are also available for even greater levels of strength. They weigh more, but the fact that they are on the short side of the rocker arm means the extra weight isn't felt as much as if it were on the spring or valve, and the increased power that comes as a result of the improved valve control more than makes up for it. The good news is you don't require expensive Spintron equipment to determine what you need. Pushrods aren't that expensive, so you can simply pull the rocker arms, install a set of the same length of your smaller existing pushrods, and see if they improve your lap times.
Air Filter FlowIf you are racing on dirt, it can be tempting to go to the local auto parts store, buy a cheap filter, and throw it away at the end of the night. They are cheap and easily replaced, but a paper air filter can cost you power.
Paper filters are designed for over-the-road use, and while they may flow well enough when clean, their design does not allow them to absorb much dirt and dust before airflow is affected. A paper filter is top loading, meaning that any dirt or dust it filters out is trapped on the outside edge of the filter. A cotton gauze performance filter is depth loading, meaning that contaminants are trapped throughout the thickness of the filter material. A cotton gauze filter can hold considerably more without affecting engine performance. It is more expensive than an OE paper filter, but the performance filter will pay off in the long run because it is cleanable and will last a season or more.
Rigid RockersIf you are racing in a pure stock class, you are probably subject to a rule limiting you to the stock stamped steel rocker arms. The problem with stock stamped rockers is they are mass manufactured and not held to the type of tolerances any engine builder would like.
That's why many valvetrain manufacturers have their own stamped steel stock replacements. Many of these, such as Comp Cams' High Energy rockers, look almost identical to stock stamped steel rockers but are held to much higher tolerances and can actually make a difference in performance just from better valve control. With a visual inspection, it is very difficult to tell the difference between a stock piece and a stamped rocker with a higher ratio. Aftermarket rocker arms with a different ratio probably aren't legal in the strictly stock classes, so take this tip with a grain of salt.
Cut The Gaskets Modern intake gaskets are usually quite good, but it is possible to sometimes get a variance that allows part of the gasket to protrude into the intake tract. This obviously isn't good for getting the maximum amount of air and fuel through the intake and into the combustion chambers. Check your intake gaskets against the intake ports in the cylinder head and the runners on the intake to see if any portion actually interferes with the ports. If you find anything, you can safely cut away small portions with a sharp razor blade. If you have large chunks of gasket in the way, it's a sign you either have a poorly matched gasket or fitment problems that should be investigated further.
Pocket PortingYou can spend big bucks getting your cylinder heads ported, but improving what is typically the worst choke point in most stock-based cylinder heads is quite easy and something you can do yourself. It isn't the runner, but the bowl area, that requires the most help in either the intake or exhaust port in a cylinder head. The bowl is the part of the port that sits directly behind the valve. A lot of classes will allow you to hand work the first 11/42 to 1 inch underneath the valve seat, and even if your sanctioning body won't, it is quite difficult to tech because it is impossible to see without pulling the heads.
The key is to resist the urge to go crazy in there. Using a carbide cutting tool and a few sanding pads, grind down the portion of the valveguide that extends into the bowl area until you have created an upside-down cone shape. This is the biggest choke area. This small change can make quite a difference in your port's ability to flow either air and fuel or spent exhaust gases.
Roll The CylinderHeads One of the biggest problems with stock heads, especially the standard Chevy 23-degree head, is valve shrouding. Shrouding occurs when one side of the valve is so close to the cylinder wall that it impedes airflow. One way to reduce shrouding is to roll the cylinder head. This simply means to deck the cylinder head on an angle so that more is cut off the exhaust side than the intake side. This changes the angle of the valve relative to the cylinder walls (lowering the angle).
This is a procedure that will cost you a few hundred bucks at a machine shop, even if you supply the heads. That's because not only must the heads be cut, but also the bolt holes must be enlarged or slotted to account for the new angle, and the intake manifold must be cut to match. You don't want to go too extreme because it can be easy to spot with just a visual inspection of the engine. But an extra 0.050 inch cut off of the valve side is hard to spot and will reduce the valve angle by about half of a degree. It isn't much, but it is enough to make a difference in engine performance.
Here's an as-cast iron head...
Here's an as-cast iron head for comparison.
The bearing on the right has...
The bearing on the right has been modified to reduce its surface area with the journal. This helps cut friction. You can do this by cutting more chamfer into the bearing on a lathe, but be careful not to distort the bearing or scar up the babbit.
Many racers don't trust a...
Many racers don't trust a mechanical advance system in the distributor and prefer to lock it out. But using one can help improve low-end power if you have a tendency to lug the engine on slow restarts.