August 2010 Chevy High Performance Q & A - Performance Q & A

Kevin McClelland Jun 17, 2010 0 Comment(s)
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The other downfall is that the chambers are 118cc. You can clip them about 0.035-inch and get them down to 115cc, but you really start cutting into the intake valve seat. As you stated, the 110cc oval-port heads give you a static compression ratio of 9.6:1. With the larger 118cc chambers you'd drop the compression down to 8.75:1. With the camshaft installed in the ZZ502, the lower compression will drop your idle vacuum, and power will drop significantly.

So stick with those oval-ports. You'll be very impressed with the massive torque this engine puts out. It'll make your '67 a real blast to drive.

Let's Get Wired
Q: I'm building a street/strip Nova for my brother while he's away making license plates, and I can't get her to start up all the time. Usually she just gives me the starter "click" and won't even try to turn over. The motor is a 383 SBC, around 10:1 CR; the starter is a Powermaster Ultra Torque and has been bench tested and works as it should. The battery is a brand-new, fully charged DieHard Gold with 795 CCA. I have a kill switch mounted at the back of the car and a junction block under the hood to provide power for the fuel pump, fan, small air compressor for rear shocks, and ignition. I have it wired as follows: battery ground to unibody near passenger-side rear wheelwell, battery hot to switch, hot side of switch to starter and junction block, alternator directly back to battery hot, and then I have one ground strap from the engine block and one from the fender to the subframe. Everything works: the lights, compressor, pump and so on; the car just won't start. Electrical has always been my weak spot and any help would be appreciated.
Via email

A: Wow, where does one find a brother like you? Very cool, and thanks for the nice wiring diagram to explain your wiring. Usually, when the battery is relocated to the trunk it's a ground problem.

You have the battery grounded to the unibody near the passenger-side wheelwell, and then you have a ground strap attached from the block to the subframe. You also have a ground strap going from the fender to the subframe. The factory subframe is mounted in rubber, which insulates the subframe from the unibody. The only chance of a ground is through the strap from the fender to the subframe. Usually there is too much paint between the fender and the body where it attaches to have a very robust ground. After many years of trying to use the unibody as a ground path for battery relocation, we went to running a ground cable directly from the battery to the tailhousing of the transmission. This ensures a direct ground path from the battery to the engine block via the trans case. We've never had a ground issue with battery relocation since. Even on full-frame cars, we run ground cables from the battery to the trans. It just gives another level of insurance that you won't have an issue.

We've seen where the battery will try to find a ground through anything. It usually attacks the trans shifter cable and welds it together! Install a ground cable and your starting issues will be a thing of the past. Hope your brother appreciates all your hard work, and again, very cool.

Old-School Buggy
Q: I have a '70 LT-1 with original pistons, 76cc heads, and a Chet Herbert cam, and the specs are 0.480-inch max lift, 248 degrees duration at 0.050-inch tappet lift, and 106 lobe separation angle installed at 103. I'm running a 4,200-stall converter, and the engine is installed in a 3,800-pound buggy.

The problem is timing. I need to get 36 degrees at 3,000 rpm and 16 degrees at idle. Right now it is 20 degrees at idle and 42 degrees at 3,500 rpm. I achieved this using manifold port for vacuum. I would like to get rid of vacuum and somehow make stop bushings for the mechanical advance. Is this possible on a stock HEI? MSD does it; why can't a stock HEI achieve the same? Also, do you think an Edelbrock Torker II with a carb spacer would be OK? Max rpm is about 7,200 rpm.
A fan
Lansing, MI


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