Part of the allure of building an engine is the challenge you find within the smallest details. Checking parts down to the thousandth of an inch is part and parcel to making reliable horsepower. While most of us have no trouble putting a short-block together, we stumble when it comes to the cylinder heads. Typically, we'll buy a new set of heads and assume that because they are new, they must be correct. Nothing could be further from the truth in some cases. And it's up to you to find and correct the problems before they cause damage or cost you power.
We've found several tips for making reliable power and helping to make the task of checking the heads a bit easier. There are also some trick performance parts we found that will make your heads last a whole lot longer. So copy and laminate these pages, then put them in your toolbox for easy reference any time you are playing head games.
Spark Plug Depth
With so many different heads on the market today it's important to be sure you're matching the right components to your particular set. Most head manufacturers take the time to carefully test that particular spark plugs will work. They usually list specific spark plug part numbers in the instruction sheet that comes with the heads. If you want to run different plugs than those they recommend, be sure to get plugs with an equal "reach." That way, the correct amount of the spark plug will protrude into the combustion chamber. Too much or too little can cause problems, and the pistons may even hit the plugs if they're way too long.
Pictured here are two Autolite plugs in a Dart Pro 1 head. On the left is a plug that's too short, and on the right is one that is the perfect length. The plug on the right is known as a Surface Gap plug and features no ground strap to speak of. Rather, the spark has four distinct points to jump to, creating a more reliable arc even under extreme cylinder conditions. Also remember to apply anti-seize to the first set of plugs you install in your aluminum heads and follow up with a light coating of anti-sieze on every other set of plugs you install. Too much anti-seize can cause detonation in the chambers, so never apply it past the end of the threads.
Color Me Perfect
If you've recently purchased a cc'ing kit to measure your chambers and ports, there's a clearer way to see your fluid. Most cc'ing experts agree that ordinary rubbing alcohol is the best fluid to use because it completely evaporates. But alcohol is hard to see, and most guys simply add food coloring to it. Buying your rubbing alcohol already dyed mint green is an easier way. This stuff is normally sold to people that use it to sterilize their mouths, but it's only a few cents more a bottle and is easy to see. Besides, it smells nice too.
Suck It Up
After you're done cc'ing your heads with your new mint green alcohol, use a Mighty-Vac hand vacuum pump to get all the alcohol back out of the chamber. You simply attach a narrow tube extension to the hose and suck it into the plastic collection can that comes with the Mighty-Vac pumps. This is also a good way to double-check your measurement because you can pour the alcohol right back into the burret and see if it refills very close to the top. You can also use the Mighty-Vac pump to remove some alcohol from your burret if you over-fill it.
Not all spring heights are created equal. Most of the time installing new valve springs is a simple process. But if you're gong to run a cam with more lift it's wise to increase your spring's installed height. The easiest way to measure spring height is with a mic like the one you see here. But you can also use a snap-gauge and micrometer. Installing or removing shims under the spring creates equal heights for every spring. Also, if you're using multiple shims, always run the thickest shim in contact with the spring. Springs can cut through thin shims, and if there's no shim or steel cup under it, the spring will gouge aluminum cylinder heads and ruin them in no time.
Teflon PC seals are the most widely used type of valve stem seal on the market today. Installing new PC seals can be a real pain in the neck without the right tool. This seal installer from Powerhouse is designed to surround the seal as you simply push it on. Information: Powerhouse Products, 3402 Democrat Rd., Dept. SC, Memphis, TN 38118, (800) 872-7223, www.powerhouseproducts.com.
After installing your new valve stem seals, it's important to check retainer-to-seal clearance. Using a dial caliper as shown will tell you exactly how much lift you can run until the retainer smashes the seal. It's wise to stay about 0.020 inch below that number to counter-act any possibility of valve float or bounce. Different types of seals will offer different clearances, so be sure to check. It's also a good idea to check this if you have already run the PC seals with no problems but are planning to increase rocker arm ratio for more lift.
Valve Stem Height
This step is important but often only done on high-end engines. Comparing and correcting valve stem installed heights is critical to performance. This valve stem height-checking tool from Silver Seal Products comes with numerous adapters to fit any type of head. If these heights are not equal, then each rocker arm will have to be measured, and different length pushrods will have to be cut for every valve. Stem heights can be altered by switching valves around, by machining the valve seat deeper, or by cutting a small amount of material from the valve stem tip. Be sure to consult with your machinist before you start cutting parts. Source: Silver Seal Products Company, P.O. Box 1050, Dept. SC, Trenton, MI 48183, (800) 521-2936.
New aluminum heads often come with the spark plug threads less than perfect. Powerhouse Products offers this spark plug thread chaser that will clean and fix any bad plug holes. While it's best to chase the threads with the heads off the engine, you can fix crossed threads with the heads on the motor by applying a liberal amount of grease to the chaser and running it in. The grease will hold any chips, and you can carefully wipe the grease out of the hole afterwards. The chaser is made to fix threads for both 14mm and 18mm (5/8 and 13/16 hex) plugs. There's even a rubber O-ring on the chaser to hold it in a socket if you're doing this in the car. Information: Powerhouse Products, 3402 Democrat Rd., Dept. SC, Memphis, TN 38118, (800) 872-7223, www.powerhouseproducts.com.
Seal The Threads
This step is a headache saver. Factory Chevy blocks, excluding Bow-Tie racing blocks, all have head bolt holes that run right into the water jackets. And hot, pressurized water will definitely make its way up past the bolts if you don't properly seal the threads. While we haven't found the perfect sealer for every engine yet, GM's Teflon thread sealer seems to work well in most cases. Apply a liberal coating around the entire thread surface and let it "tack up" for a few minutes before installing the bolt. High-temp RTV silicone also seems to work, along with Permatex Form-a-Gasket, if you apply it to both the bolt and inside the hole and let it tack up before threading the bolt in. Of course, no sealer will work in dirty threads, so be sure to always clean and chase the head bolt holes with solvent and a thread-cleaning tap like those available from ARP. Sources: ARP (805) 278-RACE (7223), Nearest GM Performance Parts dealer (800) 577-6888.
Anytime you install new heads or even change your head gaskets to a different thickness, you should always verify correct pushrod length. The ideal pushrod length will cause the rocker arm's roller tip to sweep evenly across the valve stem tip with it centered at about mid lift. Too short a pushrod will put unnecessary stress on the valve stem tip as it tries to push it towards the outside of the head. And too long a pushrod could put the roller tip over the edge of the valve at max lift. Adjustable pushrod length checkers are available from all the major cam companies. Remember that big-blocks use two different length pushrods and small-blocks use a different length still, although exhaust and intake are the same length in most small-blocks.
Port The Studs
It's a necessary evil that rocker arm studs must protrude into some of the intake ports. Sometimes the protrusion is so minor that it won't hurt performance at all, but other times the stud can create a serious obstacle for the air to move around. It's wise to check each stud that protrudes into the ports before installing the heads. If the stud sticks in the port as much as shown here, then torque it in place and use a carbide cutter to contour it to match the port wall. This is an important step even if you're not porting the heads since not all ports have a rocker arm stud in them, and they will flow differently otherwise. Always remember to seal these threads to prevent oil from being sucked into the intake ports.
Here's an area that you can port at home without fear of completely ruining your cylinder heads. The casting on the sides of both the intake and exhaust valves may already have been plunge cut by the manufacturer to ensure adequate valve clearance and good flow at low lift. However, you can improve low lift flow further by opening these areas up with a die grinder. We like to lay a copper head gasket, like this one from SCE, on the head to see just how far we can open the chamber. We use a copper gasket because its bore is perfectly round, just like the cylinder, while a composition gasket may not be round.
You don't have to use the copper gasket when you assemble the motor, just be sure that the composition gasket you use does not cover the area you opened up. Also make sure to never grind this area beyond the cylinder bore diameter. It's best to check and scribe the area you wish to grind using a gasket with a bore slightly smaller than your cylinder. When done correctly, this newly opened up area will enhance low-lift flow and will add only a small volume to the chamber, so it won't kill compression. Source: Specialty Component Engineering (SCE Gaskets), 1122 West Ave. L-12 Unit 111, Dept. SC, Lancaster, CA 93534, (800) 427-5380, www.scegaskets.com.
Race motors get torn down often, and constantly removing and retorquing the cylinder heads can get you stuck, literally. The problem occurs when, after repeated retorquings, the aluminum at the top of the bolt hole begins to collapse inward. This grabs the stud and won't let go. We've seen guys using an engine hoist hooked to the rocker arm studs, trying to pull the stuck heads off with no luck. Stepped washers like these from B&B Performance are the answer. After the head has been drilled with the special, stepped drill bit shown, which is also available from B&B, the steel washer gets pressed into the hole. That way the aluminum can never collapse around the stud again. Source: B&B/Steph's Performance, 699 Cross St., Lakewood, Dept. SC, NJ 08701, (732) 367-8700.
We're always talking about proper valve spring height and its importance to making reliable horsepower. What do you do if your valve springs are not all correct? If your springs are too long when installed, the easiest way to shorten them is to use shims under the springs although there are other ways to correct the problem, like using these different height retainer locks from Crane. These locks can move the retainer up or down 0.050 inch. If you need to shorten spring height by more than 0.075 inch, using the -0.050 lock eliminates the need to stack multiple shims under the springs. Or if the spring is already too short when installed, you can move the retainer up by using the +0.050 lock. Source: Crane Cams, 530 Fentress Blvd., Dept. SC, Daytona Beach, FL 32114, (904) 258-6174, www.cranecams.com.
You wouldn't think that there would be much to correctly installing rocker arms, but think again. There are two areas that need to be addressed when bolting on any aftermarket rocker. Both involve proper roller tip placement on the valve. Ferry's Aluminum Cylinder Head Repair has designed a rocker geometry checker to help you put the tip where it belongs. You use the geometry checker with the valve at half lift to see if the roller is centered on the valve. Ferry's tool is easy to set up and use and comes with detailed instructions and a "Zero" standard for reference. If your rockers are off, you can change the roller tip's position by lengthening or shortening your pushrods. Or if you are running shaft rockers, you'll have to shim or machine the shaft mount pedestals.
Another area to check when installing new rocker arms is if they are centered over the valve tip from side to side. Adjustable pushrod guide plates are the cure for that problem, and they can be purchased from Isky Cams (323) 770-0930, www.iskycams.com. Any misalignment here could be disastrous if the roller tip slips off the valve, and since an off-center roller will try to push the valve sideways as it opens, it will cause undue heat and wear on the valve guides. Ferry's has several other unique valve train checking tools designed for the serious engine builder that can be purchased by calling (972) 557-3565 or writing to: Ferry's Aluminum Cylinder Head Repair, 710 Quietwood St., Dept. SC, Dallas, TX 75253.
Crane has worked closely with NASCAR and NHRA teams in developing a titanium retainer that won't fail even under the highest loads. To cure the problem Crane developed its 7-degree "Posi-Stop" retainers. The specially engineered retainers feature a stepped design to reinforce the bottom of the retainer. This increases the retainer's strength and eliminates the lock's ability to "pull through" the bottom. The Posi-Stop retainers are lightweight, come complete with machined locks, and are available to fit 5/16-, 11/32-, and 3/8-inch valves. Source: Crane Cams, 530 Fentress Blvd., Dept. SC, Daytona Beach, FL 32114, (904) 258-6174, www.cranecams.com.