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Discussion Starter · #1 ·
93 LT1, going to install headers and 2500 stall convertor. I already installed 3.73 gears in the rear. just looking for a cam with the old school muscle car lope/choppy idle. I was thinking about the Lt4 hotcam but that may be a little tame with 3.73's and a 2500 stall. give me some ideas and sound clips if you have them. thanks :cheers:
 

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Lumpy Cam??? LOL guess that has nothing to do with the camera that got tossed around on the handlebars of my Quad...and nows its all lumpy in spots and doesnt work...:rolling:
 

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Discussion Starter · #3 ·
Lumpy Cam??? LOL guess that has nothing to do with the camera that got tossed around on the handlebars of my Quad...and nows its all lumpy in spots and doesnt work...:rolling:
well I guess all cams are lumpy if you think about it :D what I should have said is one with a lopey/chopy idle :thumbsup:
 

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that LOPEY IDLE is the result of REVERSION in the intake runners screwing up the air/fuel mix at low rpms, THIS KILLS LOW RPM POWER, YOU really don,t want that , what you want is maximum power over as much of the rpm range as you can get it, and matching the cam sellected, to the rpm range your drive trains gearing and other components in the engine are expected to make and use that power, in.
back in the 1960s cam design and carbs was limited enines to a much greater degree than now, its no longer necessary to sacrifice almost all low rpm performance to maximize the upper rpm efficiency. today engine, design, improved runners,cams and EFI can provide a much greater effiective rpm band.

sellecting a cam that lopes just for the sound is old school and sure to cost you power and loose races.....if you insist comp cams has cams designed to provide that lopey idle
http://www.compcams.com/information/whatsnew/NewsDetails.asp?ListHistoryID=1178823631


would you rather SOUND mean or BE FAST?

but IT WILL COST YOUR HP to SOUND MEANER and RUN GENERALLY RUN A LESS EFFECTIVE POWER CURVE......KEEP in mind with todays vastly improved technology (MPFI )FUEL INJECTION,COMPUTER CONTROLS, AND ROLLER CAMS ,you can open and close the valves far faster and maintain more cylinder pressure and use that cylinder pressure far more effectively


ISKY HAS THIS TO SAY
"What Causes Intake Reversion? Once and for all, let us have the TRUTH!

With the proliferation of the Motorsports Industry over the years, many new faces have come on the scene. In the cam grinding business today, there are many younger, less experienced companies struggling for recognition of their talents and a few have turned to postulating new theories in order to attract attention. However, they are I believe unfortunately, too often guilty of shooting from the hip.

Two in particular are responsible for perpetuating the "myth" that an earlier opening of the intake valve (even by a mere 2 or 3 degrees) causes the phenomenon known as "reversion". Nothing could be further from the truth! This misconception not only defies common sense, it also establishes a false premise from which other, incorrect conclusions can be drawn. Simply put, those who focus on overlap are on the wrong end of the cam-timing diagram!

Reversion, carburetor/Injector "stand-off" or the general effect of the backing up of the intake Fuel/Air charge normally associated with longer duration high-performance camshafts is actually caused by a Later Intake Closing! How do we know this to be true? The answer lies in the basic principles of physics. For as with geometry and trigonometry, these sacred truths do not change simply because someone chooses to ignore them in an attempt to garner a reputation.

Specifically, when the intake valve opens some 40 or more degrees before T.D.C. at the end of the exhaust stroke, very little (virtually no) exhaust gases remain in the cylinder. The piston is in the vicinity of T.D.C. (only .425" down the hole @40o BTDC - on a typical 350" Chevy with 5.700" rods) and no appreciable threat is posed to the forthcoming intake charge. The "False Reversion Hypothesis" taken to an extreme would lead one to the equally false conclusion that any overlapping of the intake and exhaust valves is totally undesirable. Automotive engineers of the late 1800's and early 1900's used to think this way. They were deathly afraid of overlap, so much so they actually employed "Negative" overlap (minus 5 or 10 degrees) to be absolutely sure none would occur. What was the result? These engines were severely "throttled back" or limited to low speeds and mediocre output. [ Reference: Iskenderian's Tech Article "Cam Degreeing is Simple"] But, more progressive engineers of the early 1920's who performed "brazen experiments" with longer duration cams proved these overlap fears to be only so much "stuff and nonsense", as both power, rpm and performance were actually improved. These engineers demonstrated that overlap did not cause engines to quiver, backfire or lock-up on the spot! Although, the ignorance displayed by their predecessors is easily explained by their lack of experience, (internal combustion engine design being in it's infancy) it was none the less the result of an incorrect hypothesis.

Should you need further persuasion that reversion is not caused by earlier intake opening and the resulting extension of valve overlap, consider this: What happens when you advance any camshaft? The intake as well as the exhaust valves open earlier. Does this advancing of the cam cause more reversion? Of course not. Throttle response and torque are enhanced. Yet, if these theories were correct wouldn't the engine run more poorly, especially at lower RPM? The answer is obviously yes, and because so, these theories are invalid. A brief look at what's happening on the other end of the valve-timing diagram will tell you why.

For when a camshaft is advanced, not only do both valves open earlier but they of course also close earlier - and here in lies the key to reducing Intake Reversion. Close your intake valves earlier and any tendency for the occurrence of Reversion or the backing up of the intake charge as the piston rises on the compression stroke will be reduced. It's not complex, nor is it a mystery. And the circumstances surrounding it's occurrence have not changed. In fact any experienced mechanic could tell you as much, for, as Ed's good friend the legendary Smokey Yunick might say, "Only country smarts are required to solve the problem."
 
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