May 2012 Chevy High Performance Q&A

Richard’s at it Again

Kevin McClelland Mar 22, 2012 0 Comment(s)

You have a great question about the Vac-u-Pan system. If the crankcase vent is before the O2 sensor, there’s a chance you are introducing free oxygen in front of the O2 sensor. In addition, if you have slip-fit collectors you must ensure that they are not allowing air to make its way into the exhaust stream ahead of the sensor. The Vac-u-Pan system is a good crankcase vent system, but it really doesn’t draw much vacuum on the crankcase. You can plug the header collector and run a filter breather on the left side valve cover while using the O2 sensor. Once you are finished tuning you should remove the sensor to prevent lead fouling. They will last around 10 hours of running before the sensor starts dying. After you have the car dialed in, get the sensor out of there and only use it if you run into issues with the performance of the car, or you’ve changed the combination.

Thanks for the kind words about the column. If we all keep helping each other out maybe we all will get a little smarter. Every time we think we’re getting a little sharper one of our cars will put us right back in our place!

Charging Problem

I’m having some trouble with my charging system. I have a ’69 Camaro with a 383 and 700-R4. The battery (Duralast Gold) is in the trunk. Both the positive and the negative battery cables are four-gauge. The negative cable is grounded to the frame at the rear bumpstop bracket. The positive cable goes to a battery disconnect switch, and then to the starter. The alternator (Powermaster 100-amp, internally regulated, one-wire, 25/8-inch pulley) is connected to the starter with a four-gauge wire. There is also a four-gauge wire from the starter to a junction block on the radiator support. The junction is where almost everything else is connected (electric fan, front wiring harness, MSD box). The engine block is grounded to the frame, again, with a four-gauge wire.

When I drive (cruising around), the voltage is at 14 V. I don’t seem to have any problems while driving. At idle or low rpm (at stopxlights or in traffic), it slowly drops below 11-12 V, as low as 9-10 V. When the volts drop, I give it some throttle, and the volts come back up but drop again unless I keep my foot on the throttle. When the fan (Flex-a-lite Black Magic, 15-inch, 3,300-cfm, puller) comes on, it draws a lot of voltage. I don’t drive much at night, since I don’t want to draw more by turning on the lights and find myself with a dead battery on the side of the road.

I didn’t seem to have any problems before the battery went in the trunk, but I would like to keep it in that location. I’ve been told that maybe I should try switching all the four-gauge wiring to 0/1-gauge, or maybe a smaller diameter alternator pulley.

The battery, starter, and alternator are all new within the last year or so. I think I’ve done everything short of rewiring the whole car. I want to add a stereo system and fuel injection, but without the proper amount of voltage, I’m sure they won’t work correctly. What do you suggest? Thanks for your help.

Rick Umipig
Renton, WA

We’ve covered battery relocation questions several times, but you have the answer in your letter and we want to see you out driving your Camaro. First of all, anytime we relocate the battery to the trunk we use 0/1-gauge welding cable. Welding cable is a very fine-stranded copper conductor. The current actually travels across the top of each strand of the cable. With the fine-stranded wire, you get two benefits: outstanding current-carrying capacity, and flexibility to get into difficult locations.

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