Make your own free website on Tripod.com

 COMBO POWER

1953Corvette1.jpg (13696 bytes)                PerpCutout.jpg (13760 bytes)

Up      

 

(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.

Remember… Calculating Torque into Horsepower:

1 HP = 33,000 ft-lb/min (= 550 ft-lb/sec)  or    (1 Metric HP = 75 Kilogram- meters/sec)

If Torque (Brake or corrected brake) = 325 ft/lb–                                                   Horsepower (brake or corrected) =Torque x RPM                                                                                                        5252        

Example: = 325 x 2000   = 124 HP @ 2000 RPM                                                                                                       -----------------5252

(Torque = Force x Distance)

 

Stock Compression -Standard Bore (4.030) 350 CI Chevy Compression Ratio With flat top pistons. See Chart below..                                                          
Head cc’s  - Compression Ratio

58                          11.0:1

62                          10.5:1

64                          10.3:1

68                            9.8:1

76                            8.8:1

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 Headers

Dyno: Vacuum =9in/hg

Horse power      Torque     RPM

339                    330       5400

                          392        3800

Power good but poor torque at low RPM

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 Headers

Dyno: Vacuum = 14in/hg                                                                                                                                           Horse power    Torque          RPM

328                   345            5000                                                                                               

                         408            3600                                                                                 

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

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

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

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

 

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 mile