Braking News
Q.Is it safe to drill my own brake rotors? Given the price difference between stock and drilled rotors, I'm considering using a pattern and drilling them on my drill press and then counter-sinking the holes. Problems?
Thanks, and I'll look for your answer in Street Rodder.
Bob Hargreaves
Via the Internet
A.Quite a few years ago I asked one of the foremost manufacturers of headers why he no longer offered the Try-Y design that worked so well on small-block Chevrolets. He replied that since most of the drag cars in magazines had equal-length, four-tube, g-race-style headers, he "couldn't give Try-Y headers away." Despite the fact that Tri-Ys made more low and midrange torque and were probably a better choice for street use, hot rodders saw the four-tube style on race cars, so that's what most of them wanted." Basically it was the "if it makes a race car go fast, I want it on my street rod" theory. The same holds true for drilled rotors.
Race cars used drilled rotors because under severe braking conditions the friction pads can get so hot that a gas is created. That gas creates a sort of "cushion" between the pads and rotors and, as a result, braking efficiency is reduced dramatically; holes in the rotor merely give the gas an escape path.
While there isn't a street rod on the planet that will ever encounter this problem, they became the things to have once drilled and slotted rotors began showing up on a few high-profile magazine cars. As a result, many of the brake system component manufacturers and suppliers responded to the demand. So, do street rods really need drilled rotors? No, they don't. Holes, slots, your initials-they are all cosmetic rather than performance enhancements. On the other hand, none of that stuff hurts anything either, so if you like the look, go for it.
That being said, if you opt for drilled rotors, don't do it yourself. Buy those that have holes put in them during manufacture. Drilling rotors later is an invitation for cracks, and cracks will impact braking, although not for the better, and they don't look good either.
More Braking News
Q.I have a '29 Ford coupe with a 454 Chevy. I'm having troubles with the brakes on it. I originally built it with manual brakes but recently upgraded to power brakes. That's when my problems started; the front brakes lock up after only a few pedal strokes. I've replaced the master cylinder, power booster, and combination valve. I also added residual pressure valves but still have the same problem. I've bled the system with a vacuum pump and the old buddy assisted method with the same results. Any help you can provide is greatly appreciated. Rick SmithVia the Internet
A.The next time the brakes lock you'll probably find that opening the bleeders on the calipers will release the hydraulic pressure in the system and the brakes will unlock. There are a number of reasons for the system to retain pressure and the brakes not release, but since the problem started after the power booster installation, we should start there. Here are a few things to consider:
Is the master cylinder compatible with the power booster (did they come from the same source)? Make sure the pushrod from the booster is adjusted correctly and allows the pistons in the master cylinder to fully retract when the brake pedal is released.
Are you using a disc brake master cylinder? A manual brake master cylinder will have a built-in residual pressure valve that will hold too much pressure in the line when the pedal is released and cause disc brakes to drag.
Check to see that the brake pedal returns properly; it may be necessary to add a return spring.
You mention a combination valve and that you installed a residual pressure valve. Most combination valves have a residual valve built in so an additional residual pressure valve would be redundant. In fact you may not need one at all. You didn't mention where the master cylinder is mounted, but you don't need one at all if it's on the firewall. If the master cylinder is under the floor you won't need more than a 2lb residual valve. If you've installed a 10lb valve, that's more than likely the problem.