Lack Of Oxygen
Q
My '73 Camaro has a freshly rebuilt 350 small-block Chevy. It's bored 0.030 over, with 9.73:1 forged Speed-Pro pistons, Edelbrock RPM aluminum heads and intake manifold, an Edelbrock 750-cfm carb and hydraulic flat-tappet RPM camshaft (234/244 duration at 0.050 inch tappet lift, 0.488/0.510 inch max lift), Summit lightweight roller rocker arms (1.5:1 ratio), hardened pushrods, and a windage tray. The ignition is handled by an MSD 6AL box, distributor, and plug wires and a Flame-Thrower coil. Exhaust runs through 15/8-inch full-length headers and 21/2-inch Delta Flow 50-series Flowmaster mufflers. This is all going through a TH400 with a Stage 1 shift kit, a 12-inch B&M Torque Master converter, and a 10-bolt posi rearend with 3.73 gears.
My problem is with all of these parts, my car is too slow. My best time at the track is 14.9 seconds. My best 60-foot time is a 2.41seconds with a top speed of around 93 mph. Even though I race at 5,000 feet elevation, I feel this car should be quicker. I have even had it at a local auto shop with a chassis dyno. After three hours on the dyno and numerous timing and carb jet changes, I didn't gain anything!
Also, I am using a drop air cleaner with a 2-inch element versus a 3-inch element. When I do this, it leaves me with a quarter inch between the top of the air cleaner and the hood (I know I should get a cowl hood). When you look at the air cleaner with 2-inch element, there is roughly 5/8 inch between the top of the air cleaner and the bottom. While at the track, I even took the air cleaner off and still saw no change. Could my problem be the wrong stall converter? If so, what would you recommend? A friend has a B&M Hole Shot 2400 that he'd let go for $50. I was also recommended to try a Hughes 3,000 converter. Also suggested was a bigger full roller camshaft, like a Thumpr by Comp Cams. Any thoughts would be greatly appreciated.David JohnsonAlbuquerque, NM
A
The engine package you've put together is a dyno-proven package by Edelbrock. You should be right in the power range if you were at sea level. The lack of barometric pressure is not feeding the engine with the oxygen it needs. Since you spent the dollars on the chassis dyno, and we will assume that the operator/tuner knew what he was doing, you have all the power you're going to produce. When you rebuilt the engine, did you degree the camshaft in to ensure the cam was ground correctly and that the timing chain set was proper?
Looking at your package, you have honed right in on the problem. The torque converter is way too tight. The Torque Master converter from B&M is a great RV torque converter for a truck or very stock engine. The Edelbrock RPM Performance Package would need a 3,000 stall at sea level. This same 3,000-stall converter at 5,000 feet would probably only stall to 2,500 rpm because of the lack of torque output from your engine. To wake up your Camaro, try a Nitrous Hole Shot 10 converter from B&M (PN 20482). This is a great converter, which specs out by B&M to stall around 3,600 rpm behind a small-block. Again, this is at sea level. You'd probably see this converter stall around 3,000 rpm in your hometown.
Finally, you really need to do something about your air cleaner. Putting the lid of the air cleaner that close to the float bowl vents and making the air squeeze between the base and lid and turn down into the carb is really tough. Yes, we understand it ran the same at the track with the filter on or off. We assume you have a 14-inch open element air cleaner assembly. If this is the case, why don't you go with a K&N XStream Top Air Filter, PN 66-1401? This air filter lid gives you a large filter area built right into the lid of the air cleaner housing. This would double the airflow of the filter assembly you have now.
The last thing you'd want to do is install a larger camshaft. This would reduce your cylinder pressure even more and kill what little torque you have. If you were to install a larger-roller camshaft, you'd need to lower your rearend gears significantly and go even higher on the stall speed.
Try the things listed above and compare your performance to other vehicles at the track on a given day. That will be your best gauge of performance. Don't expect the sea-level performance you see in magazines.
Sources: bmracing.com
knfilters.com
Technical questions for Kevin McClelland can be sent to him at chevyhi@sourceinterlink.com.