Knowing your front-end geometry is an exercise in patience and mathematics. Even Winston C
Regarding Reverse Rotation
Q: I have heard of reverse-rotation engines, but haven't seen any articles on the subject. I would like to know the process for converting an engine to reverse rotation (cam, ignition, valvetrain, oil pump, starter modifications, etc.). What kinetic/gyro effects would result?Guy LavertyVia E-Mail
A: Years ago, I did some work with Smokey Yunick on reverse-rotation engines. My recollection is that Smokey said they were "a hell of a lot more trouble than they're worth when you consider all the changes required." In fact, while you're likely to see some reduction in chassis torque that favors less left-front corner lift, there are some related suspension tuning issues that also require rethinking. So even if you get past the mechanical problems involved with changing crankshaft and camshaft rotation and solve technical requirements of the ignition and oiling systems, there are on-track situations that require attention. Maybe Smokey was right. He often was.Jim McfarlandAutocomAustin, TX
Editor's Note: If you wish to do further research on reverse rotation, reference Smokey Yunick's report on it in the May 1991 edition of Circle Track. While it is too large to reprint here, the article covers all your questions in Smokey's own inimitable style.
Needs More Vacuum!
Q: I need some help! I run a 406 small-block Chevy. The specs are fresh block, scat crank, Eagle six-inch rods, flat-top forged pistons, Edelbrock RPM heads, cast-iron factory four-barrel, high-rise intake and open three-inch pipes from stock exhaust manifold.
What I need is two more inches of vacuum. Will mufflers help? Will a restrictor plate under a factory Quadrajet? I tried moving timing, and I can get 18 inches, but I need 20. The cam is a .410 lift Crane Saturday-night spec.
A: Scott, it's hard to tell exactly what you need to do without seeing your engine, but I can give you a couple of ideas to check out. You asked about mufflers, and there's a possibility that might help a little, but there are two bigger things that probably will help you more.
I don't know where you have the cam in the engine, but it might help to advance the cam just a shade, two or three degrees. That should help your vacuum some. The other option is likely to make the biggest difference. You don't say, but I have to assume from the other specs you gave that you are running a hydraulic cam and lifters. Competition Cams makes a lifter called a Hi-Tech Hydraulic lifter that actually bleeds down. That should definitely get you the two more inches of vacuum you need. It doesn't hurt your engine at all and it helps to get the vacuum down when your engine is being checked, but once the rpms get up there it all straightens out and does just what it's supposed to do.Jay DickensJay Dickens EnginesAberdeen, MS
Formulas in Mark Chevalier's story "Wrapped Up in Traction Control" (Nov. '01) were misprinted. The formulas appeared correctly, without the exponents. The formulas with exponents are as follows:
To calculate wrapup stiffness with a pull bar:
S = 4.77 * K * h2 * (1 - .005 * t)
To calculate wrapup stiffness with a lift bar:
S = 4.77 * K * L2
h-distance from the axle centerline to the pullbar mount
t-angle of the pullbar
K-distance from the axle centerline to the line of action of the spring
Send your questions
Direct your Track Tech Questions to Track Tech, Circle Track Magazine, 5555 Concord Pkwy. S., Ste. 329, Concord, NC 28027, or send us an email at ctrack@emapUSA.com.