Dennis Wells (Wells Racing Engines) is no stranger to the pages of this magazine. For more than 40 years he has built engines for a wide range of racing and high-performance street vehicles. Because of his combined success and longevity, we recently cornered him with some specific questions about his building experiences. There are lessons to be learned from what follows.
What's the most frequent issue you face when a customer's engine doesn't perform up to his expectations?
Well, most of the time it's generally not the engine but the tune-up that's been applied to it. Obviously, conditions like atmospheric pressure and temperature can change from the dyno to the track or the car isn't handling properly. Like if it's pushing in the corners and it lugs the engine down, they don't understand that if you exit a corner 20 miles an hour lower than you need, you'll be going 20 miles an hour slower at the other end. It's incorrect to assume that just because you've got a lot of horsepower you can make up a difference like this, but you can't. It's not so much about power as it is torque and where it's produced in the rpm range. Of course, gearing can also come into play.
For example, I had a customer in here today who had just switched from alcohol to gasoline and he says the car won't come off the corners like it did. I explained to him he gave up a lot of lower rpm torque by making that change and he needed to gear the car lower. Engines are packages, and cars should obviously be geared to take the most advantage of where torque is produced. In a case like this, the lower gearing will spin the engine higher and then adequate valvespring pressure comes into play. You just have to look at the complete package.
Are there any areas of engine building that are more critical than others?
Today, I think the most critical issue is adequate valve clearance. Camshaft design and technology has changed considerably in recent years, resulting in much faster valve movement. Years past, the rule of thumb was 0.080-inch on the intakes and 0.100-inch on the exhausts. That's not true today.
I've seen instances where if the cam's ramps were rapid enough, piston-to-valve clearance needs to be as much as 0.130-inch and the valves still lightly touch the pistons. You've really got to be careful about camshaft selection and the amount of required valve clearance. This is generally not a problem on intakes as much as the exhausts, like always.
Not only do some of these cams 'pitch' the valves but cause them to bounce during closing, especially on the exhaust side. You just need to strike a balance between how much power you want or think you need compared to how much maintenance you want to do. And you can't overcome the problem with more valvespring.
The worst case I've seen was with an engine that just wouldn't make power above about 7,000 rpm. I'd been using this same combination for years with no problem. Come to find out, the pushrods were flexing. I switched from a 5/16 0.080-wall pushrod to a 3/8 0.120-wall pushrod and it was like a 50hp difference.
I guess my point is that the most critical areas aren't areas at all, but the fact that parts packages need to be treated exactly that way. In this case, you might have thought more spring pressure would've solved the problem but, in fact, it would've made it worse.
Once an engine leaves your shop, how do you deal with parts failures when the problem was caused by the customer and not the part?
If it's a loyal customer, I mean like one who's been with me for quite a while, I'll provide the labor free and maybe split the parts costs with him, depending on the situation. But if he's not going to be coming back or goes out and "bad mouths" you, that's not an attitude that makes me want to help with the repair costs. It then becomes a business decision based largely on the attitude of the customer.
Sometimes I'll fix a problem that I know was not my fault because I plan on making that money back over time with additional work for that customer. I mean one bad customer who's out there "bad-mouthing" you is just terrible. Most people don't pay much attention to comments about how good a particular motor turned out. They just remember the criticism. You get a bad name out there, even if you don't deserve it, you're in trouble. It sometimes makes good business to just fix stuff to avoid a problem like that.
You've had years of experience running chassis and engine dynomotmeters. what would you say are the benenfits of each type of testing equipment, along with any drawbacks they create?
Let me give you a current example of how these compare with each other. I just had a customer's Sport Mod car on the chassis dyno. A lot of these guys run Quadrajet carburetors and pump gas is the fuel. We're not talking about much horsepower from these motors, probably around 400 or so. Sort of a "working man's" race car class.
The problem with the Quadrajet is that when the secondaries open up, it tends to break the tires loose, so they're really sensitive to tune. He sends me his motor to run on the engine dyno, and it's just about impossible to properly adjust the secondary function to produce best track performance.
Just because it can be made to run clean on the engine dyno doesn't mean it's going to handle the transient loads presented at the track. I feel like the engine dyno is the best for doing research where you're looking for maximum power. You can't do this on the chassis dyno.
For example, if a customer doesn't bring me the same tires and rear gears he runs at the track for testing on the chassis dyno, we won't get the same readings (power levels) he'll get at the track. They always want to compare power levels with their buddies and I have a hard time convincing them that's not the reason you use a chassis dyno. There are just too many variables involved.
I can change rear tire pressure and change the power. Chassis dynos are unbeatable for getting best on-track driveability. At the end of the day, each type dyno has its own purpose, just like any machine, and you've got to choose between them based on what you're trying to accomplish.
The one thing I want to emphasize is for racers to not misunderstand what they can and can't derive from testing on either of these types of equipment.
On the track, the load sensed by an engine during acceleration is not constant. If fact, it decreases as the mass of the car is accelerated, up to the point where aerodynamic resistance overtakes lower speed inertial resistance. Unless an engine dyno is built to accelerate a mass, like a heavy flywheel that simulates car weight, you can't determine transient load conditions as a car experiences on the track. A chassis dyno will at least approach this condition where an engine dyno can't.
As I previously said, WOT power measurements should be confined to an engine dyno. Any other type of power evaluation or tuning conditions belong on a chassis dyno.
As professional engine builder, what is the most difficult part to becoming successful?
I guess it boils down to developing an ability to deal with a wide variety of customer personalities. Different people want to be treated differently with respect to what they expect from you. For example, I have this longtime customer who called me eight times today. I mean, if every customer called me that many times a day I'd never get anything done. But you just have to learn how to deal with it. It's like any business where you need to learn the personalities of your customers to know how they want to be treated as well as how they treat you. Of course, we all have an ego and it's really important to not only recognize your own but those of your customers.
In your recall, what's the most successful project you've completed?
That's easy. I think putting in our SuperFlow chassis dyno and beginning to run Sprint Cars on the rolls is it. I mean, nobody had ever done that before. Even the SuperFlow engineers gave us a blank look when we told 'em we wanted to start to run Sprint Cars on the dyno. Even they didn't know if it would work. And you can't imagine all that we've learned using that technique.
Of course, once we did it, seems like a lot of other shops started doing the same thing. It just makes sense. We've now been doing this for about 11 years with no dyno problems at all. In fact, I've got 14,800 runs on that equipment, maintenance-free. I think I've greased the U-joints one time. Can you imagine that? Especially when you're starting Sprint Cars on the rolls, in gear and with all the shaking and counter-loading going on. It's brutal.
Also in your recollection, what is the most humorous experience you've had?
Well, we've had our share of these but probably the time a guy left a rag under his carburetor. He put on the carburetor, engine wouldn't start, having all kinds of problems, called me up and he finally managed to get it started. He called me again and said he had bits of rags shooting out all the headers and wanted to know what he should do. Funny thing is he didn't damage anything but he said there was red lint going everywhere. I'd like to have seen that one myself.