For the simple fix, swap out the too-big camshaft for something a little more conservative. If you would back the duration off to the 220-degree range, it would be much happier. The 2,500-stall converter you have now will be happy. The heads would get by, but that would be our next change. Check with Comp Cams or Crane for your camshaft of choice.
Do Ya Feel Lucky?Q I currently have a mild 350 with a 3970010 block, 882 heads, an Edelbrock Performer cam, a Performer manifold, and a 1406 Edelbrock carb. The current engine was rebuilt a few thousand miles ago and runs great, but I have no idea what parts are in it. My '69 Camaro also has an original Super T10 four-speed, and a new Moser 12-bolt with 3.42:1 gears. My Camaro is street driven but needs more horsepower, so I recently purchased the Trick Flow 420 top-end kit from Summit Racing. The kit includes the 23-degree aluminum heads, a cam, lifters, pushrods, roller rockers, head bolts, and gaskets. The cam has 228/234 degrees duration at 0.050 inch tappet lift and 0.480/0.494 inch max lift, makes power to 6,000 rpm, and requires between 9.5- and 10.0:1 compression. I also purchased an Edelbrock Performer RPM manifold. Since the engine is in the car and runs great, I haven't dropped the oil pan to find out if it's a two- or four-bolt main.
My questions concern the bottom end. I've heard mixed opinions on whether I should go with a forged crank, rods, and pistons, or stay with a cast bottom end. Some say to go all forged, and others say just the rods and pistons but use the cast crank. What would be best for my situation? Also, if my block is a two-bolt, should I convert it to a four-bolt or is this a waste of money? I will have the assembly balanced once I decide what to use. I don't plan on racing or using a power adder. Thanks for your time.Dennis LardizzoneVia e-mail
A Forged components are very durable pieces. Are they necessary for a 420hp small-block for street use? Well, for true insurance, forged is the way to go. However, we have used cast short-blocks for dyno and street-performance engines well into the 400hp range with no problems. The biggest concern with cast components is the max rpm allowable for the engine, including detonation. Nothing will kill a cast-component short-block quicker than detonation. Cast components are very strong, but they are brittle. Using aluminum heads and running good gas in the engine will take care of the engine knock. Also, since you are using a four-speed trans you are in control of the engine load.
There are many benefits to running cast components. First, you must run much tighter piston-to-wall clearance with cast pistons, since they do not expand like a forged piston. The tighter clearance keeps the piston rings square with the cylinder bore and gives you better sealing. The piston ring lands also keep their shape and can seal better.
As for your two- or four-bolt mains, your 3970010 block was offered with both. It was used in passenger cars, trucks, industrial engines, and even '69 302 Z/28s. If you stick with your cast bottom end and it is a two-bolt block, keep your rev limited to 6,000 rpm. This should be right at the horsepower peak of your 420 package. If it's a four-bolt, we've spun cast rotating assemblies to 6,500 rpm. Again, beware of detonation. If you wish to throw forged components into your four-bolt block, you will have a bulletproof package at the 420hp level. Good luck with your Camaro, and enjoy!
Rock OnQ I'm building a 383 for my '73 Chevy Nova and plan on running a Comp Cams Xtreme Energy 268 cam. My question is about rocker arms. I've read in several build books of people running 1.6/1.5 ratio rockers on their small-blocks, and I'm considering this combo. I have a set of Aero Head Dart II S/S heads with 2.02/1.60-inch valves. Is the rocker choice a good one or should I just run 1.5s? I was also looking at running a Performer RPM Air Gap manifold and Edelbrock 800-cfm Performer carb. Would the 750-cfm Performer be a better option? The bottom end will include Speed-Pro flat-top pistons.