I can tell you how to do a complete tear down and rebuild for your heads so they will run and look like new again. This will give you more power and fuel economy, but its going to take a lot of writing and a lot of it you may not understand right away but i will try to keep things as simple as I can. Buy the time your done reading this you will be an expert on your cylinder heads.
Your first job is to clean your heads. To minimize costs, the best plan is to scrape and wire brush the heads until they're resonably clean, especially in the areas between the valves, the chambers, and deck face. Next, spray them with Gunk, bruch that well in, hose off with high-pressure water, then dry them off. You may want to have them crack tested at your local machine shop for premium results.
With the heads clean, your first move is to inspect the guides, Ideally, these valve stem-to-guide clearances need to be about .0015-in. on the intake and .002-in. on the exhaust clearance. This is unlikley to be the case, so let's look at the maximum limits. Anything morethan .004-in. on the exhaust and .0035-in. on the intake will start to cost power because the valves will not seat properly. Also, loose guides will cause whatever valve job you do on the head to wear faster because the valve lands on the seat in a different position each time.
There is a simple way to check for excessive valve clearance that also makes allowances for the fact that the wear bell mouths the valve end of the guides. Lay the cylinder heads on a flat surface. With no oil on either the guide or valve stem, push the valve in until the tip is level with the top of the guide. Using a dial caliber, check the movement up and down of the valve. If it exceeds .015-in., valves steam clearance is excessive and needs to be fixed.
The next few moves depend on you cam and the springs it requires. If the valve spring loads are not going to exceed 220 pounds at full lift, you can, for the most part get away with the stock press in studs. However, It's worth nothing that occasionally press-in studs pull out in totally stock applications. If the combination to be used have sufficient lift to warrant a spring with more than 220 pounds over the nose, then screw-in studs should be used. The more expensive to buy and install flared hex studs are not necessary unless you have good reason to require pushrod guide plates to be installed. For most of the applications, the pushrod guide slots in the heads will get done. This means the cheaper, nore cost-effective straight shank studs, which only require the existing hole to be tapped 7/16th UNC, can be used.
If you want to save $5, pull the studs from the heads yourself. This is accompleshed by dropping two old rocker balls over the stud and then cranking down a 3/8th UNF nut to pull the stud. However, most machine shops have the hydraulic stud remover that makes short work of this job. If you're going to pull the studs and tap the hole yourself, besure to use a quality, long-taper tap that's sharp.
Now consider what type of valve stem seals will be used. I use Teflon seals, which minimize the amount of oil passing down the guide. However, since your engine will be used for the street, the Teflon seals reduce sten lubrication below what i consider is needed fir minimal wear rates. For good all-around results on the street, I find the K-line stem seal to be effective, as is the relatively new Fel Pro blue seal. In either case, the ends of the valve guides may require maching to accept these seals. If you have thick wall bronze guides installed, then these should already be machined for stem seals. I recommend only intalling positive types of seals on the intake guides as the additional lubricant on the exhaust helps heat conductivity and extends guide life. If you decide to stay iwth a stock diameter spring, and the budget is tight, then the stock umbrella seals, which shield rather than seal, are perfectly functional. However, you do need to make sure with this type of oil control arrangement that guides don't have excessive clearance, otherwise oil passed down the stem will dilute the octane value of the fuel. This will lead to an earlier onset of detonation. Apart from the carbon buildup on the back of the valve will cut airflow and power, so pay attention to valve-stem oil control.
There is so much more to tell ya but im running out of time and have to go to work. I will tell you more latter.
