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(Please excuse some of
the formatting until we get it figured out. Upon transfer format changes.)
Carbureted Engine Combinations and Power (John Myers – Vetteworks) Engine combinations vary among almost every engine. Performance enthusiasts always ask.-."What engine combo works?" We’ve decided to write a summary of results for various combinations which have showed up in numerous publications related to V-8 engines. Most are Chevy but some may vary. Without a lengthy explanation here is some good info on a number of engine combinations and other performance related topics. Engine combos follow some important information concerning tuning.
We’ll begin by talking about air. In most cases, especially in the daily drivers and mildly modified Chevy’s, speed of the air entering your intake and the runners of your cylinder heads must be remain high. In this class of cars, dual plane manifolds, mildly ported heads and proper header size is essential. Without it, the fuel/air mixture has a good chance of dropping out of the main air path and onto the surfaces within the passage from carburetor to combustion chamber. In addition to the air, carburetion should remain consistent with the volumetric potential of the engine. In other words, there’s no use running a carburetor capable of providing more fuel than your engine can burn. A Holley 850 just doesn’t cut it on a mildly modified 350. Using a 780 would be about the largest application for the same engine in a highly modified – street driven car. The only instances that would benefit from anything larger than a 750 on a 350 or 383 would be if the cylinder heads, intake manifold and exhaust were paired with a radical cam to generate enough draw to require the added CFM of the carburetor. More capacity of the engine = more CFM = bigger carb. Cams are intimidating when it comes to choosing one. All those big performance articles begin to contradict the real world when it comes to properly selecting a cam. As shown in some of the combos that follow, cams aren’t the key to a good strong engine. On the other hand, they help to bring the entire carb/manifold/head/exhaust arrangement into tune. If you don’t have the whole system working together, you may be wasting your time. Don’t pay too much attention to all the hype. Instead, read some of the publications written by the experts about small block Chevy performance. (See "Chevy Books" in the table of subjects in the Motor &Tech page.) Next time someone asks you how much lift your Cam has, tell them about the duration and how the other components are set up to deal with it. Lift is fine but if the duration is short, the lift doesn’t help unless you are running extremely high compression and large cylinder displacement. Ignition is another topic commonly misunderstood. As outlined in the table below, ignition modifications rarely gain the HP expected. They may be capable of supplying a more than adequate spark but that only means that your engine will run like its supposed to. This is a good thing but to expect large performance gains from an ignition system would be fruitless. Also, many of the performance ignition wires on the market aren’t made to last as long as those that came with the vehicle. Make sure you buy good quality wires from an established manufacturer. Also, you should make sure that the wires are properly routed away from heat and objects which may draw the spark through the insulation. This is a very common detail that is often overlooked. In most cases it will lead to premature wire failure or arcing. Use wire looms if necessary. Another good idea is to buy the spark plug wires with the crimper tool so that you can cut the wires to the correct length and install the ends yourself. If you rely on a universal application you may end up with wires which are way too long and nearly impossible to route without running into something. (And looking like crap). Spark plugs should be appropriate for the engine and driving conditions. Don’t assume that the coldest plugs are best for high performance. With a properly tuned and component matched set up, one heat range hotter should be O.K. Transmission/Stall Converter: Make sure your total timing comes in at the same time your stall converter stalls 1.) Engine 383 400 Crank - .030 over – 350 Block – 882 Cast production Heads – Comp Cams 292 Hydraulic 244 Duration, .507 In. Lift @ .050 – Edelbrock Performer RPM – Holley 750 – 1-3/4 in HeadersDyno: Vacuum =9in/hg Horse power Torque RPM 339 330 5400 392 3800 Power good but poor torque at low RPM ¼ Mile – 13.15 @ 104.8 MPH 2.) Engine 383 400 Crank - .030 over – 350 Block – 882 Cast production Heads – Comp Cams Dual Energy 275 219/229 Duration, .461/482 lift at .050 – Edelbrock Performer RPM – Holley 750 – 1-3/4 in HeadersDyno: Vacuum = 14in/hg Horse power Torque RPM 328 345 5000 408 3600 ¼ Mile – 12.97 @ 104.7 MPH 3.) 350 .030 over (355) – Edelbrock Performer intake – Edelbrock Q-jet carburetor – 1-3/4 headers – 882 Heads (1.94/1.5 valves) – Crane HMV-266 cam (210/216 duration @.440/.454 lift)Dyno: Vacuum = NA Horse power Torque RPM 285 332 4500 355 3500 ¼ Mile – 13.78 @ 97.50 MPH 4.) 350 .030 over (355) – Edelbrock Performer intake – Edelbrock Q-jet carburetor – 1-3/4 headers –#6073 Edelbrock 70cc Aluminum heads (9.5 CR) – Crane HMV-266 cam (210/216 duration @.440/.454 lift)Dyno: Vacuum = NA - Horse power Torque RPM 339 356 5000 395 4000 ¼ Mile – 13.14 @ 103.2 MPH 5.) 350 .030 over (355) – Stock iron heads – GM HEI distributor – cast iron exhaust manifold – Cast Iron manifold - Q-jet carb Dyno: Vacuum = NA Horse power Torque RPM 278 292 5000 343 3500 ¼ Mile – 13.99 @ 96.05 MPH 6.) 350 .030 over (355) – Stock iron heads – GM HEI distributor – cast iron exhaust manifold – Performer Aluminum dual plane manifold (P/N 2101) - Q-jet carb Dyno: Vacuum = NA Horse power Torque RPM 293 308 5000 346 4000
¼ Mile – 13.84 @ 97.5 MPH 7.) Points vs Electronic – 5.7 GM Crate motor 5.7 GM crate motor – 9.5:1 Corvette aluminum heads – Crane HMV 272 Cam – Edelbrock Performer Manifold – Holley 750 Carburetor – 1-3/4 Headers – Turbo Mufflers RPM 2500 3000 3500 4000 4500 5000 5500 New single point 346 355 364 *370 363 334 298 New HEI 343 354 360 *369 359 335 303 New MSD Electronic 345 357 363 *367 360 335 303 distributor w/6AL box and Blaster 2 coil * = Peak Horsepower 8.) 350 (Rocker/Roller differences and Engine Combo) 1.5 Inch Rockers vs 1.6 .030 over (355) – pocket ported 882 cast iron GM heads (9.1:1 CR), Weiand Dual Plane Intake – Holley 750 – 1-5/8 headers Crane Roller Rockers RPM 1.5" Rocker HP 1.6" Rocker HP + Gain 3250 221 218 -3 3500 240 237 -3 3750 263 257 -6 4000 280 283 -3 4250 302 303 +1 4500 316 317 +1 4750 324 336 +12 5000 345 347 +2 5250 346 354 +8 5500 350 364 +14 5750 351 353 +2 6000 334 343 +12 1.6 Rockers + .02 ET and .20 MPH improvement in ¼ mile
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