|
|
(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?" Weve 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 will begin by talking about air. In most cases, especially in the daily drivers and mildly modified Chevys, 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, theres 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 are'ntt 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 dont have the whole system working together, you may be wasting your time. Dont 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 doesnt 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 arent 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 junk). Spark plugs should be appropriate for the engine and driving conditions. Dont 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 9.) 350 - Standard performance engine - Cast 1.94 I/1.5 E 76cc, 9.5:1 Compression ratio heads - Cast iron Intake - Q-Jet carburetor - 1-5/8 Dia. Headers - MSD distributor - 38 deg total mechanical advance - 3896929 Chevy cam with 258/268 duration at .050 lift: .390/.410 RPM Horsepower Torque 3500 250 375 5000 294 280 10.) 350 - With cam and intake system modification (A) - GM cast iron heads - 1.94/1.5 valves , 9.5:1 compression ratio, 76cc combustion chambers - Edelbrock Performer Intake manifold - Holley 650 CFM carb. - 1-5/8 headers - MSD Distributor - 38 degrees total mechanical spark advance - Cam = R.T. TM252 252/264 Duration - .430/.450 lift @ .050 RPM Horsepower Torque 3750 280 392 5000 317 333 11.) 350 - With cam and intake system modification (B) - GM cast iron heads - 1.94/1.5 valves , 9.5:1 compression ratio, 76cc combustion chambers - Edelbrock Performer Intake manifold - Holley 650 CFM carb. - 1-5/8 headers - MSD Distributor - 38 degrees total mechanical spark advance - Cam = R.T. TM264 264/276 Duration - .450/.470 lift @ .050 RPM Horsepower Torque 3750 277 388 5250 337 337 (no typo) Note: Cam duration brought the horsepower curve up and kept it there longer but torque suffered lower down the RPM band 12.) 350 - Modified - GM "492" cast iron heads w/ 2.02/1.6 valves, 64 cc Combustion chambers, ported w/ three angle valve job - 11:1 compression Ratio - Holley 300-36 Intake - Holley 750 Carb - 1-5/8 headers - 38 deg. Total mechanical spark advance - Comp Cams 292H, 292/292 duration - .501/.501 lift @.050 RPM Horsepower Torque 4000 298 391 6500 403 326 Note: This is a high performance street set up with a cam which works better in the higher RPM range. The longer Duration of the cam cause the Torque to suffer significantly at lower RPM. Higher compression causes mid range torque to come up quicker. A dual plane manifold would make this set up more suitable for the street. Idle would be a bit on the rough side. 13.) 350 - Modified Tuned Port Injection -GM "492" cast iron heads w/ 2.02/1.6 valves, 64 cc Combustion chambers, ported w/ three angle valve job - 10:1 Compression Ratio - TPIS Modified manifold, runners and plenum, stock throttle body with air foil screens removed from M.A.F. sensor - Magnum PROM - 1-3/4 headers - TPI Hydraulic cam - 278/286 duration - .490/.510 lift @ .050 RPM Horsepower Torque 4250 340 420 4750 356 394 Note: As with many TPI setups, high end horsepower takes a hit because of the long plenum.runner system of the TPI engines. On the other hand, you'll get plenty of low end torque as a trade off. Definitely a fun setup for the street. Count on steady power until about 5000 RPM. After that is when the TPI begins to suffer. Engine throttle response is also a good trait of the TPI. 14.) 350 - Modified with TPIS Mini Ram - GM 492 cast iron heads w/ 2.02/1.6 valves, 64 cc Combustion chambers, ported w/ three angle valve job - 10:1 Compression Ratio - TPIS Mini Ram stock throttle body, stock throttle body with air foil screens removed from M.A.F. sensor - Magnum PROM - 1-3/4 headers - TPI Hydraulic cam - 278/286 duration - .490/.510 lift @ .050 RPM Horsepower Torque 4750 344 380 5750 400 366 Note: Obviously the Mini Ram made up for the decreased air flow of the TPI system. Here a gain of 44 horsepower was traded off for 40 lbs. of torque at the lower end. The RPM band also jumped up 1000. 15.) 431 H.P. 383 - Brodix -8 Cylinder heads with 2.02 I/1.6E valves, 68 cc Combustion Chambers - Manley pistons (49453) - 5.7 in. Connecting rods - Edelbrock Performer manifold - Holley 750 Carb - 1-3/4 headers - MSD Ignition - 36 degrees total mechanical spark advance - Competition Cams special hydraulic roller - 280/286 duration -.525/.560 in Lift @ .050 RPM Horsepower Torque 4000 344 452 5000/5500 431 429 Note: The 383 offers excellent torque due to its increased stroke. In addition to this, the quick valve action due to the hydraulic roller provides adequate valve opening during the shorter duration of the cam. 16.) 626 H.P. Supercharged 350 - Dart II cast Iron Sportsman heads with TRW 2.02 intake and 1.6 exhaust valves - ported and polished - 68 cc chambers - TRW Forged (L2441F-30) Supercharged pistons - Weiand 6-71 blower - 2 Holley 600 CFM Vacuum sec. carbs - 1-3/4 headers - MSD Distributor - 32 degrees total spark advance - 9% overdrive - 10 lbs boost - Comp Cams hydraulic roller 286/286 duration - .560/.560 lift @ .050 RPM Horsepower Torque 5200 569 575 6000 626 548 Note: All I need is a car to put it in. Don't forget about the drive train for this set up! The contents of this site are copyright © 2000, Vetteworks, All rights reserved |