For many engine builders the bread and butter business is in cylinder head work. In fact, according to our 2005 Machine Shop Market Profile (also available at www.engine-builder.com) 41 percent of gas and 54 percent of diesel engine builders’ business comes from servicing cylinder heads.
And one of the most important aspects of doing this work is the valve job that you perform. Do it properly and profits as well as a good reputation for doing quality work are likely to come your way – do it poorly and the job is surely on its way back to you. But to “do it right” in today’s competitive market, you need up-to-date equipment that can handle all the complexities of today’s engines.
Cylinder heads typically require guide and seat work to restore compression and oil control. For the valve to seat properly and to gain the most power and efficiency, engine builders must replace or bring back to spec all valve seats and guides. Seats that are cracked, loose, sunken or otherwise destroyed must be replaced with new. Drilling, reaming, replacing valve guides, removing worn, loose or damaged valve seats, cutting new seat counterbores and machining valve seats are all part of the reconditioning process that your shop must be able to handle as efficiently as possible and with precision accuracy.
There are basically three types of seat and guide machines on the market today. The first type of machine is what is sometimes referred to as a “drill press” machine. This type of seat and guide machine has a solid column for the tooling and the table floats to move from guide to guide. These are very basic seat and guide machines and have some limitations compared to some of the more advanced machines, however, some smaller shops are using these still. A small shop may not be able to justify the more expensive machines and also don’t have the volume to be concerned about doing hand grinding and lapping.
One manufacturer who sells floating table machines said they offer a lot of vertical travel and may be more universal, therefore more appealing, to some smaller operations. Some manufacturers even offer seat and guide machines that also do surfacing. So you can actually get more than one machine for the price of one.
The second type of seat and guide machines is the floating powerhead machine. This type of machine is virtually the standard in many engine builders’ shops today. Our research shows many of these machines are in the same price range (roughly $25,000-$30,000). On these machines the cylinder head remains stationary below a floating powerhead. The powerhead floats above on flat ways, which adjust front to back and side to side.
The powerhead weighs much less than the cylinder head you’re working on, so when you center it (and they all center similarly), you float the powerhead and center it with the pilot. Then when you let off the foot pedal to lock it in place, you will have a very rigid platform.
Many of today’s cylinder heads have canted valves in them also, and on an old-style machine you have to tilt the fixture in order to do canted valves. Therefore, for each guide you have to relocate the fixture. On new-style seat and guide machines the powerhead tilts and you simply adjust the powerhead for whatever angle you need. Once you’ve to set the powerhead angle you can go up and down the line with the same degree of tilt for each valve seat, whether it’s 7 degrees, 9 degrees or more. Most new-style machines can accommodate 15 degrees or more.
Today most seat and guide machines use three-blade carbide cutters with three-angles or more built into the cutter itself. These cutters are called form tools and give you a very consistent profile and seat width for every seat since it’s all built into the tooling. Some manufacturers offer slightly different tooling but the basic principle is the same: a form tool with built-in angles.
The third type of seat and guide machine is the live pilot design. There are two types of pilots: live pilots and dead pilots. A dead pilot remains stationary in the guide as the tooling rotates, whereas a live pilot spins with the tooling in the guide. You have to be very precise when fitting live pilots into guides or else there could be too much play and result in a seat that isn’t concentric. Some live pilot machines have a single blade carbide cutter that can adjust while it spins to create almost an infinite number of profiles.
Winona Van Norman offers several seat and guide machines, but its most popular seat and guide machine is the VSG-4720. According to the company, this machine is designed for precision, speed and versatility. It features precision leveling, which includes an electronic level and a digital readout for more precise leveling of the cylinder head. It uses a ball drive system that will automatically compensate for small deviations in guide alignment, and a fixed pilot design that locks in the guide.
“We use what we call a ‘dead pilot’ design,” says Ed Keibler, Winona Van Norman. “In other words, you push the pilot in the guide and the tooling spins on the pilot so that way you can control the tolerances. Probably the biggest difference between our seat and guide machines and others is we use a 3? spindle and have a greater range in rpm from 0-640 rpm. The VSG-4720 also uses an air clamping system to lock the powerhead in place when you let off the foot pedal.”
T&S developed a ball drive system for seat and guide machines in the early 1990s and has since designed a complete machine to go with it. The company offers a unique machine, which it says is quite popular with performance shops and others who do a lot of V8 cylinder head work. The TX2000XL can set up two V8 heads at the same time, so you can machine a set of heads very quickly without having to change the fixture for each head.
“You put the heads in and get them straight, and we have a way to qualify them straight to the deck surface,” says Tim Whitley, Sr., T&S Machine Products. “Once they are straight, we can use the deck surface to cut all of the seats to the same height relative to the deck surface. And if we have both heads in there, we can do all of the heads at once. For example, we can do all of the intakes on both V8 heads without changing our setup. We can also roll the heads over and do the spring seats, also without changing the setup. So it’s very fast to do a set of heads.”
“Between Sunnen and DCM, we offer basically four machines,” says Tim Meara, Sunnen Products Company. “All four of our machines are true seat and guide machines where you can install guides, seats, put three angles on the seats, etc.
All Sunnen’s machines have floating powerheads, where the workhead floats on ways above the cylinder head. The cylinder head is clamped down in a solid fixture beneath the powerhead and it is moved to the cylinder head.
Sunnen’s VGS-20 machine has been on the market for a number of years, and Meara says a few manufacturers have cloned this type of machine since then. According to Meara, the VGS-20 was the first seat and guide machine of its design on the market. It was originally a Tobin Arp design until Sunnen bought that company.
The VGS-20 features a tilting head to compensate for the angle on the valve seats. It can tilt up to 15 degrees, which is more than most canted valve angles. Meara says the tilting capability is well within what today’s cylinder heads require – stating that the most cant he’s seen is about 8.1 degrees.
The VGS-20 features 3-angle single blade cutters; fixed pilot design and ball drive automatically compensate for deviations in guide alignment, which eliminates additional setup time from guide to guide. The lightweight powerhead “air-floats” on rails above the table, and the pneumatic clamp system locks the powerhead in position when the air-float pedal is released. The universal fixture handles any size head and rotates 360 degrees, locking in any position. The spindle tilts at any angle up to 12 degrees either side of vertical, speeding up setup and machining of heads with canted valves. And you can dial in any spindle speed from 20 to 420 rpm without stopping rotation; you can even go in reverse for tapping.
With Rottler’s new SGF8 model seat and guide machine you can machine heads of all sizes from a small motorcycle head to a large Caterpillar diesel head. The SGF8’s rigid carbide centering pilots are manufactured to less than one-tenth of an inch tolerance and combined with the lightweight air-float workhead ensures precise centering and concentricity. The CNC ground carbide seat cutting inserts are available in many different designs to suit every engine builder’s requirements, single angle, multi-angle, or curves and radius shapes are available.
“Ever since we have incorporated the seat and guide system into our product line, we have been continually developing new techniques to simplify the process and maintain a high degree of accuracy on every valve seat,” says Luis Rodriguez, Rottler Manufacturing. “Cylinder head technology has changed over the years to the point where older equipment is not as accurate as today’s seat and guide machines. Our fixed [dead] pilot system can hold tolerances of .0002? to .0005? concentricity on every seat. Our carbide pilots aren’t tapered but straight, similar to a live pilot design, and meet the same diameter and angle as the valve guide.”
Another important factor Rodriguez points out is that seat materials are much harder today and to machine them you have to reduce spindle rpm to as low as 45 rpm in order to cut them properly. The SGF8 has a fine feed wheel that allows you to clean the seat in order to achieve the correct finish, height and concentricity.
Newen offers a fixed-turning system that is very different than most other methods for machining valve seats. Newen’s Elite Power Contouring (EPOC) system uses a single point cutter spindle to machine cylinder heads much like a CNC lathe, which allows you to create profiles that would be very difficult to produce with traditional machining methods.
“When you use the single point system, it works much like a CNC lathe: you generate the profile, you don’t plunge anymore,” says Brice Harmand, Newen. “You interpolate two different axes. The machine calculates the feed and spindle travel for the profile you’re creating, and then you cut with a single point, triangular cutter, which only cuts with the very tip of the point. You don’t exert pressure instead you generate the profile. You can do much more complex profiles and longer profiles with a fixed point system.”
With a range of seat and guide machines, Peterson offers a machine for a variety of budgets. The TCMV25 seat and guide machine is engineered for high productivity, according to the company. The rugged heavy-duty column supports the powerhead without vibration or deflection. The 360-degree rotation air table allows precise positioning of the cylinder head for cutting seat angle with three-angle cutter blade tooling. And the standard #3 Morse taper lets you make quick tool changes as well.
Peterson’s ASV/A valve guide and seat machine is a full-featured floating powerhead machine. The air-balanced spindle gives you positive control over all of the machining operations. And the pneumatic tool change allows for rapid tool head changes in between machining operations. In addition, the positive stop alignment air-clamping fixture makes setting up four valve cylinder heads quick and easy. The ASV/A features a variable speed powerhead with 15 degrees of spindle tilt each direction, and tooling for three-angle carbide seat cutting inserts.
Valve Guide Machines
For shops that want a separate workstation to do valve guides, some manufacturers offer valve guide stations for guide work only. You can drill and ream guides and install new ones as well.
K-Line offers three different valve guide stations. “Our top of the line model is actually a valve guide boring stand,” says Tom DeBlasis, K-Line. “You start with your boring motor, and it’s a high-speed reamer that you install valve guide liners with. It hydraulically clamps down so you get a very straight hole, so you can install liners or oversize stem valves. One remanufacturer we know of uses it to bore out the guide hole and then uses an .015? over reamer to install oversize valves.”
Cal Valves has a Wet Reaming Station that allows the flexibility to ream more than one type of cylinder head and valve guide bore without a major tooling change. By using four standard stem sizes for all of their valves, regardless of intake, exhaust, make, and model, you are able to ream the guides for a wide variety of heads in a fraction of the time it would take to replace, knurl or sleeve the guides and install OEM valves.