When you consider that engines often turn close to or even more than, 7,000 revolutions per minute, all those pieces had better be the right ones and, just as importantly, installed correctly.

We spoke to a number of engine builders and picked their brains about the most common mistakes at-home rebuilds can yield. Thanks to their help, maybe you can avoid some or all of these and successfully go over your power plant with race-winning results.

Heads

Joe Rhyne of Rhyne Competition Engines builds stock car engines for pavement and dirt as well as just about any other racing need, including marine. He narrowed down heads as a prime area for mistakes—and not just building them.

“Something as simple as the cleaning of the head is often critical,” Rhyne says. “The cleaning process can hurt aluminum if products like abrasive pads are used. It’s about being careful with it. You should use a sharp scrapper and remove items such as gaskets carefully. People can hurt heads in the port areas by taking off up to .003 of metal when they remove gaskets.”

Rhyne says rebuilding or freshening your own heads can often lead to trouble for those who don’t know.

“One of the biggest mistakes made is when he’s starting out with a quality head, and doesn’t recognize what makes it a quality head. They re-do it and change it and reduce the original quality of the airflow. They can affect the low lift, mid and high lift flow numbers, and actually reduce their horsepower.”

That’s because heads are the most complicated part of an engine, and within that maze are plenty of traps to contend with.

“The condition of the valve guide and the valve stem need to be considered,” Rhyne says. “If you’ve got excessive wear, taper or out of roundness, you can’t machine the seat concentric to the valve guide centerline. Also, if you did machine the seat with the valve running out, it will ‘beat the seat out prematurely’ as we like to call it. The valve then moves around randomly and wears the seat down like a hammer on metal.”

It comes down to equipment, Rhyne says.

“Most people can’t do their own valve job. They don’t have valve grinders or the machinery for cutting valve seats, and even if they did, there’s more to it than that. The blending of the valve angles is the critical part. You hear people talk about three-angle valve jobs. It isn’t just about multi-angle valve jobs. The actual angles are critical depending on the cylinder head, as are the blending of the chamber and bowl areas. The top seat angle is actually in the combustion chamber, and, when you machine the seat, the extreme OD of the cutter can leave a step in the combustion chamber. That’s the part that has to be blended so you need hand tools such as a stone or a real fine carbide then a polishing spiral.”

So, what’s a home-builder to do when it comes to something as tricky as heads?

“The bottom line is that they should take their heads to a quality engine builder that can treat them as such. That way, they can go forward instead of backwards,” Rhyne says.

Parts Selection

Darrell Poe is the NASCAR Weekly Series 2000 national Mechanic of the Year. He’s also won the Mechanic of the Year regional award four times. He says choosing components is a matter of matching the rules one is running under.

“It’s determined a lot by the rules which govern the class of racing or the type of engine you’re building,” Poe says. For general parts selection, he says, “Stick with reputable quality parts and stay away from cheaper quality, mass-produced, imitation or reproduction parts.”

While every racer wants more power, building an engine is also an exercise in restraint. Avoid the “some is good, more is better” syndrome— especially when it comes to critical components.

“A common error that many engine builders make is to over-cam the engine with too big a cam. Ideally, what you want to do is match the carb and cylinder head characteristics to the cam and rod length combination for that particular engine,” Poe says.

He says that with so many changes over the years, it’s easy to get lost in the cam shuffle.

“Cam lobe profiles have advanced so far in the last few years, so there’s more to choose from. Selection is critical. If your association has well defined rules, you have a small range of cam selection. The other end of the spectrum is if your association has minimal rules on cams, pistons, etc. That opens up more avenues to you. The best way is to select a cam for the rules and track you’re running. Engine rpm and how long they need to stay up is also part of the equation.”

Assembly

When it comes to assembly, there are plenty of danger areas. We asked Gary Wagoner of the Richard Childress, Lowe’s #31 Winston Cup car what to watch for. He’s been the head engine builder there for over seven years and has caught some mistakes. He quickly pointed out one problem: “Getting the rings upside down.”

“If you get the second ring upside down you’ll have an oil problem. That second ring is the one that scrapes the oil off the cylinder wall. The top ring, if it’s off, will reduce power by not sealing off properly.”

So, what’s the smart way for avoiding ring problems?

“Look closely,” says Wagoner. “There are marks on the rings — a little dot faces the top. Also, there is a bevel on the inside of the ring that faces down when properly installed.”

Wagoner says that when assembling the short block, the correct torque is very important to performance and the life of the engine.

“You need the right torque on all main studs and rod bolts. Your heads need to be torqued correctly and in the proper sequence. If you don’t follow the sequence, the head gaskets may not seal properly. Also, if the heads aren’t torqued properly, there may be bore distortion and that can create a loss of power.”

Wagoner reveals one more trouble area.

“After degreeing the camshaft, you need to check the valve-to-piston clearance. It is very critical.”

Details

Ron Hutter of Hutter Racing Engines builds a variety of engines for stock cars—from East Coast Modifieds to Winston Cup. He ranks being thorough and showing attention to the details high on the important list for home builders.

“Pay attention and don’t be in a hurry,” Hutter says. “It’s been documented that ring clearances, gaps, back clearance on the rings, bearing clearances, rod side clearances, end play on the crankshaft, and thrust surfaces being aligned are all very important. Then there’s the clean environment issue of engine building. Keep it clean. I can’t say enough about that. Leaving corruption in various places in the engine will destroy it for you,” Hutter says.

He also provides some critical points to check on heads even if they are done outside the shop. “On heads, don’t get too close to (valve spring) coil bind; watch the clearance between valve seals and valve retainers; it depends on the lift of the cam. You don’t want to see the springs hitting the fulcrum of the rocker arm—that’s got to be clearanced just right. Pay attention to your rocker arm geometry.”

He also points out a fact about assembly lubes. These are used on the various threaded parts in the engine for assembly, and need to match up with the specifications created by the component manufacturers. “Pay attention to the proper lubes. Different lubes can dramatically affect rod bolts, head bolts, main bolts/studs stretching during assembly. Look at the recommendation from the fastener manufacturer,” he says.

The bottom line in home engine building is if you’re not sure, ask. The knowledge is there; but, remember, there’s a lot of information. If you think you’re sure, double check. Race engines are like racing itself—constantly changing. If your information is outdated, or even wrong, guess what your results will be.