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Performance Machining

A Look At Performance Engine Building Opportunities

By Doc Frohmader

There’s rebuilds and there’s rebuilds. I’ve gotten used to referring to the vast majority of rebuilds as taxi-cab builds. That’s because the majority of rebuilds tend to be cookie-cutter stuff where the primary goal is to restore the original performance of any given engine. Based on stock and stock replacement components, builders use a somewhat standardized set of machine operations aimed at building reliable, if mundane, power plants. Then there’s performance building.

Performance building ideally takes the standard operations and bumps them up to a higher level. Parts are more expensive, stresses on components higher, and machining steps become more critical to making an engine live at high performance levels. And not only are the operations performed with more care and sometimes to higher standards, but additional operations are often required.

This little nugget of wisdom simply means that there’s an opportunity to set your shop up as exemplary and build a reputation for high-end machine operations. I’m sure you already know that reputation can mean more income. People are generally willing to pay more for skills and experience that are perceived to exist in these high-end shops. In the recent ‘recession’ I’ve seen in several parts of the country where, while the taxi-cab builder was sitting on his hands, the performance builder down the block with the reputation was desperately trying to keep up against a mountain of work.

So, you’re asking, what are some of these performance machine operations and can I take advantage of their potential in my shop? Let’s give that a look.

Blocks
The expensive blocks are the ones everyone wants and often get the most abuse. Unfortunately, they came from the same plants and processes that produced all the other OEM blocks and that means casting shift and imperfections. In addition, there’s wear and tear and outright damage. So, as you’d expect, there are several machine operations used to revitalize tired blocks. Since a 175 hp taxi-cab engine running at 3000 rpm that needs to last 20,000 miles compared to a 7000 rpm drag engine producing 750 hp and running flat out are different animals, there are machine operations or variations that can be critical.

1. Align honing. A dead-straight crank bore, properly sized, round, and in alignment with all the others is in most performance shops not optional. Minor defects can cause major disasters. In this case, the equipment used to complete the operation is specialized. It means you’ll have to invest in the equipment before you can offer the service, but the shops I know of that own the tools generally keep them reasonably busy.
2. Bore stagger and core shift correction. These kinds of operations utilize your standard boring machine and cylinder hone, but first you have to know what correction to make. I’ve recently been learning a bit more about sonic testing for this purpose. Let’s say you sonic check a block and find, for example, that you have cylinders (one or more) with a thick side opposite a thin side. While this is not necessarily a problem, you may determine the next bore size would make the one side too thin. Or, on the other hand, you are intending to make a significant bore increase and want to make sure you have maximum block integrity when you’re done. Use the sonic testing data to MOVE the bore to better position. It takes accurate and thorough sonic testing and a little finesse with the boring equipment. Also, the operation is generally used to correct end- to-end cylinder location, not in-out.
3. Lifter bore bushings. Not only do lifter bores wear over time, but it turns out OEM blocks aren’t all that perfect in terms of geometry and sizes. The best aftermarket blocks and most high-end performance stuff gets re-bushed. The bushings allow perfecting the lifter angle relative to the cam, making the cam functions more consistent and improving valve train efficiency and durability. They require less clearance so they lose less oil. They have less friction and reduce valvetrain power loss and wear.

Again, this operation requires tooling, so you have to invest to reap any profits, but the number of shops offering the service is typically small. That leaves you singing to a captive audience.

4. Installing four-bolt mains, cross-bolt mains, and girdles. Beefing up the bottom end of an engine can do a lot to prevent grenading. The time to think about this is not while you are sweeping shattered parts, oil and oil dry off the track. However, you typically need access to a mill and to an align hone. Some cases require align BORING. It’s a precision job, though, and for those who need the operation it ain’t cheap.

I worked on an old Chrysler Hemi being prepped for vintage road racing recently where a set of 340/360 Mopar four-bolt mains were machined for the Hemi. On the mill the caps were fitted and the new bolt holes drilled and tapped. The block then got the mains bored to re-size the new caps to near the correct main bore size, then the mains were align honed to re-establish a perfect crank centerline and bore dimensions. The block spent two full days on the machines.


5. Wall prep. I still see the occasional shop where some operator whose education and tech savvy stopped in the ’60s manages to convince his high performance customers that finishing with a 180 grit stone is just right – regardless of ring type or engine use – as long as he can show you a cross-hatch pattern. These same guys tend to think that ‘chrome moly’ (no such thing exists) rings are high tech wonders. Today we have the benefit of a lot of research and testing such as the fax film kits to help get this right. Listen to the ring manufacturers and equipment manufacturers, follow their prep recommendations and be prepared to explain this to your customer.

6. Miscellaneous. There’s lots more to be done for different applications. You can do special cleaning such as shake-n-bake, acid dipping, de-burring, and even polishing both inside and out. You can redirect or enhance oil returns. You can modify the oiling system passage sizes and port or port-match the pump and passages. You can fit the oil returns with screen to catch debris. You might want to alter the deck to correct block geometry or to increase compression. Every operation that you perform that your competition can’t or won’t gives you the advantage and build the mystique of your reputation.

Reciprocating Mass
You could wear yourself out trying to determine how many different ways there are to modify the moving components in the bottom end. However there are a few basics.

1. Crank grinding and prep. You either do cranks or you don’t. Good crank guys are gold. Performance crank work is an art. So if you do it right and have good equipment, you will almost certainly stay busy. Performance work is more sophisticated than Taxi cab stuff, although most of the same operations are performed. The difference is in the tolerances. Not only does the crank need to end up dead straight and have good surfaces, but there is no room for barrel or taper. Surface imperfections are not tolerated. Most of all, you have to be willing to allow the builder to work with you to achieve the bearing clearances THEY want. One size does not fit all and close is not good enough. If you intend to do performance crank work, you’ll work to very close tolerances and add several steps for measurement and calculations.

If you get into offset grinding for strokers, welding for corrections or strokers, repairing snouts and keyways, special metal treatment and hardening, knife-edging and weight reduction, you realize that just standing in front of the grinder is not all there is to it. It’s a job for a dedicated pro.


2. Balancing. I’m sure some will argue with me, but I simply will NOT build an engine any more without balancing the reciprocating mass. Imbalance causes vibrations and unpredictable variations in clearances. It sets the components up for additional stress and increased wear and metal fatigue. My position is if I intend to dump $5,000, $10,000 or upwards of $15,000 into a performance engine, I’d have to be a fool not to spend a couple hundred on a good insurance policy. You and your performance customer will definitely see positive results.
   

This is another case where the right equipment is required. However, balancing is part machining and part art. It takes time and experience to balance to zeros in an efficient manner. I’ve done enough of this over the years to know that unless you do it regularly and keep your head in the game, it’s not easy to get it done in a timely way. Modern equipment helps, what with computers doing some of the calculations, but knowing where to add or remove materials takes experience and mistakes can be terminal.

The real question you have to answer to your customer is why you are doing what you are doing. His cousin’s best friend’s uncle once built an engine and he knows how to set it up! The shop down the block sets up ALL its engines the same way and they seem to work fine!

What you have to do is explain that tolerances and clearances are application dependent. What the engine will be used for (street, drag, road race, marine, etc.), how much weight it will pull, trans type, gear ratio, performance level, rpm range, reciprocating mass size and oiling system type are all important issues and will alter the specs. Both knowing how these items affect tolerance and clearance and how to get the machining done to achieve them are critical performance building issues and need to be paid for – your customer has to understand why paying more will get him more.

Heads
Any pro racer will tell you that the power’s in the heads. What they’re saying is the ability to flow air/fuel mix in and exhaust out can be made more efficient and that’s where power comes from. Performance prep requires a lot of detailed and careful work done by someone with experience. A minor mistake typically results not in a miss but in an explosion.

The obvious machine operations are such things as porting and bowl blending or enlarging, shaping the bowl and guides, and installing larger valves. To some degree these are easy to sell if your customer has the funds because you can show the evidence of your efforts. Of course anyone can do enough grinding to make it look good, but it takes experience to make real performance improvements. Your job is to show benefit if you want to develop this kind of work. A flow bench will give you more concrete proof that what you do makes a real difference and isn’t just cosmetic.

The less obvious stuff is every bit as critical. Setting your margins, seat width, contact location, valve angles, stem heights, spring heights and spring pressures not only make huge differences in durability but in performance as well. Accommodating the cam profile is an art form. Again, this is not a one-size-fits-all deal and knowing what to do as well as how to achieve it are the difference between a pro and a hacker.

The bottom line is if you want to establish yourself in performance machine work or building you will have to invest in the proper machines and tools, you’ll need to stay up on what works and what tech changes are happening, you’ll have to step up a few notches in quality and tolerance keeping, you’ll have to convince your customer you are doing the right thing and it’s worth the money, and sooner or later you’ll have to offer proof of your skills and experience. This is one case where cream rises to the top.

Manufacturer Quotes:
Most of our tooling is aimed at the performance market, and our Multi-Bal series are totally dedicated to performance applications," says Randy Neal, CWT, Norcross, GA. "We’re balancing crankshafts and driveshafts for performance applications. When it comes to our Pro 1058 machine, it can be used for general automotive work with no problem –the key is the fact that it is very versatile. We can generally capture, for instance, a cylinder head one time and perform multiple tasks to it. This way we don’t have to lose the original registers."

Another procedure important to performance engine builders is balancing. "Balancing is one of the things you have to have to do performance work. But a balancing machine is really only single functioned. If you believe you’re in the performance market and you don’t have a balancer, you’re kidding yourself," says Neal. "It used to take for a general balance job around three hours. We’re now doing that in an hour. The machines now do all the ‘mental gymnastics’ to determine what’s wrong, where to place it, what to change and so on"

"Recently, the upper end performance people have been going to the hot-honing process," says Jack Wetzel of Sunnen Products, St. Louis, MO. "We’ve been told they’re finding anywhere from 2-5 horsepower with the process. As any performance builder knows, on the upper end of the performance scale, every horsepower you can get is valuable."

Hot honing, explains Wetzel, when done with flow-through torque plates, causes the cylinder to be most close to perfectly round and straight when the engine is at operating temperature.

"It’s not an inexpensive thing to get into, however," cautions Wetzel. "The proper equipment can require an investment approaching $80,000. So it’s something that only the very upper end customers are going for right now."

On a scale that more engine builders might be familiar with, Wetzel points out the increasing attention paid to street performance upgrades. "Particularly in the Japanese cars, we’re seeing very radical performance work. Very large sleeves in relation to the original cylinder bore are being installed – we hear stories from our customers who say $20,000 is not out of the question for THEIR customer to spend on a street engine!

"Some of the shops we call on are doing nitrous, turbos, blowers – all requiring more attention to detail. Tolerances and surface finishes are more important than ever.

"With performance work, all of the standard machining steps are neccessary. But the need for accuracy increases along with the demand for performance," says Wetzel.

"Shops today are looking for more automation from their machines," says Randy Taylor of DCM Tech, Winona, MN, "for one simple reason: they’re no longer getting the skilled technicians they once were. They need the machines to do the precision work for them."

Taylor says that an engine builder for a NASCAR team told him "they pay me X-amount of money to get one-quarter horsepower more out of a motor." Obviously in this case, money for top-shelf automated CNC machinery is no hurdle. But for most builders, cost IS a concern. In this case, automation may be even more critical, he says.

"The guy who’s building engines for the local dirt track racer may have a reputation for good performance work, but by the same token, he can’t pay a machinist like they do in Winston Cup shops. He needs to know the repeatability and reliability are in the machine, to take some of the pressure off the operator. This lets the shop owner know that no matter who’s running the machine he’ll get quality work from it. We work very hard to take the variability out of the equation."

But Taylor says shop owners also want automated machines that are capable of being operated manually. "In case the computer goes down, it won’t put the shop out of buisiness. And if the shop does have a guy who can ‘tweak’ things, it allows the user to be in control.

"They want repeatability and flexibility," Taylor says.

These days, performance customers’ demands can be summed up in one word, says Anthony Usher of Rottler Manufacturing: "Precision." Thanks to the increasing presence of aluminum blocks, engine builders are faced with a need for more precise machining capabilities than ever before. Not only are the inline four-cylinder imports seeing radical machine work but big motors such as the Chevy LS-1 are becoming more of an issue

"There’s a lot of work that goes into putting bigger bore pistons into an aluminum block," says Usher. "Normally, that involves resleeving the block because the orignal had pretty thin walls. It’s critical to get the bore centers in the right place. When rebuilders are machining these blocks, it’s not as if they’re just boring it 30-over – they need to bore it, cut steps and counterbores to get the sleeves to fit and seal properly.

"Today’s performance guys are looking for a machine that can go to a programmed center. They can determine where they want that center to be, put it into a CNC program so that the machine moves quickly to that center and repeat it.

"It’s no longer just a matter of enlarging a hole," explains Usher.

"The important thing in a performance engine block is that you bore it and deck it 90° of each other, and if you can do that on one machine, it makes things better and safer for the engine builder," says Chip Brown, Peterson Machine Tool, Council Grove, KS. "Every time you move the part you’re machining you’re asking for a mistake."

"We have two or three heavy hitting machines for performance – the camshaft grinder, the crankshaft grinders and the AC-650 boring and surfacing machine." says Brown. "From our standpoint these are the three most important machines that a performance engine builder can have."

"In today’s performance market, you’re seeing heavier and heavier valve springs and lighter running masses. So you’re getting more rpm, more load on the spring and more load on the camshafts. The camshafts are becoming more and more critical today than they used to be. And that’s why it’s so important to have your cylinders and everything lined up correctly. In other words, you’re basically talking about blueprinting an engine," Brown explains.

"Engine builders demand repeatability and adaptability to do the oddball product or part – and they need rigidity in both the machine and fixturing," says Ed Kiebler, Winona Van Norman, Wichita, KS. "To simply say the machine is rigid can be very misleading. For instance, when talking about seat and guide machines you must not only have a rigid base but also a rigid spindle and fixturing. Even with all that, there is no guarantee of accuracy if the tooling isn’t also extremely rigid, the machine accurately centers and locks in place."

Kiebler says it comes down to a few things: "In performance work you are typically trying to increase the size and reduce the tolerance while removing weight and make the surface flatter, rounder or smoother. You need infinitely variable speeds and feeds to be able to cut many of the different materials listed above. The machine must have such things as digital levels, dial depth gauges, touch-off indicators, etc., to ensure proper alignment, centering or squaring of the parts before machining."

To do performance work properly, Kiebler explains, enhancements must be made to existing equipment first. Fixturing must be beefed up while making it easy to use. "Machine speeds and feeds must be increased and variable to enable the operator to cut the different types of materials often seen in the performance market. You may need to do several operations to blocks and heads that will cause you to use a seat and guide machine to machine certain areas of the engine block. All these enhancements must also give the operator the ability to duplicate the results time after time. And as a supplier, we need to be constantly updating our tooling for each machine to keep up with the changing needs of the performance market. This is one of the most critical aspects of the equipment."

Heavy-duty and performance have been RMC’s calling card for 50 years, according to Ray Meyer, RMC, Saginaw, MI. "And basically, in the last 10 years, we’ve been concentrating heavily on the performance customer’s needs. Almost all of our machinery is developed to help build race engines. Our multi-purpose machine is used in production but also for performance because of its speed and accuracy to do engine blue printing and other performance processes."

Meyer said the demand for speed and accuracy have increased over the last few years. "Where it used to take an engine builder two to three days to work a performance engine through a machining process, now can take a matter of four to six hours," he says. "One machine, one set up. Basically, one fixture achieves a lot of the machining that needs to be done for performance. It deals with line boring, connecting rod stroker clearance, block lightening. You can do all of these operations with virtually one setup."

"If you have to take the fixture down or change it you lose your benchmark," Meyer explains. "You lose accuracy each time you move from fixture to fixture or from machine to machine. We call that stacking of tolerances. When you change machines the stacking gets higher."

By minimizing fixture changes you reduce the "stacking of tolerances" effect and can be more accurate as a result. "A rotating fixture enables the operator to machine all faces of the engine block that are typically machined in one setup," says Meyer.

"Our customers in the performance market are asking for better and more consistent bearing and wear surfaces," says Ken Barton, president of QPAC. "This requires a stable process that is tightly controlled, monitored and inspected – of course, there’s a cost for this. Additional time, manufacturing, support and inspection equipment is required, as well documentation, which all add to the cost.

"Micropolishing equipment provides customers with the latest critical surface and geometry characteristics required. Additionally, bearing and wear surfaces are enhanced using micropolishing to prepare the surface for various coatings to make the surface more damage resistant and reduce friction.

"The result? One word: performance. And it enables the customer to pursue new designs using lighter materials."

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