Performance for beginners

For a guy, or woman, wanting to modify their engine for a little more performance without losing a lot of low end, how does one go about it? Well, ASSUMING the engine is in good shape, the obvious choice would be to add a set of headers. Well, I will tell you, the "oversized" reproduction Ram Air manifolds are good for over 550HP on a mild stroker with aluminum heads and the power curve was still rising at 6,000 rpm so how bad could they be for a basically stock engine? Yes, they are more expensive than a set of D-port headers, but, you don't have to worry about them rusting out either.... and they're quiet! Ignition is the next area of concern. Hei distributors have been known to be weak at high rpm. With the addition of an aftermarket module and ensuring the distributor gear has been shimmed to limit endplay, you should have a good performer. Use vacuum advance, either ported or manifold, whichever runs best for you. Replace the stock vacuum canister with an adjustable unit and calibrate it for 10-12 degrees at idle--- use manifold vacuum for the calibration. A few benefits of vacuum advance are less throttle needed for a given idle rpm (manifold) and better fuel economy(either ported or manifold). The actual ignition curve can be manipulated as well. If your low rpm throttle response or idle characteristics are lacking, perhaps your engine needs more initial timing. Simply cranking the distributor around is not enough though because your TOTAL timing will be increased as well. On a low compression engine, it may be able to take 40 or so degrees no problem, but if it is a higher compression combo, then you will want to limit the total while increasing initial. There are weight and spring kits available for that. Induction would be the next area of consideration. With an otherwise stock engine, I would go with a Performer intake with either the stock Rochester Quadrajet or an Edelbrock 750cfm carburetor with a "strip Kit" calibration kit. Some will claim equal or better performance from the stock intake, but I will take less weight from the aluminum as an added benefit. When the time comes to dig into the engine and replace the camshaft... PLEASE, don't go too big! You will lose drivability because there is NO cylinder pressure. When one speaks of cams being big or small, long or short, he or she is usually speaking in terms of duration (the amount of time the valves are off their respective seats). So how can one replace a stock camshaft with an aftermarket performance unit and NOT lose low end performance? Focus on OTHER camshaft parameters such as AGGRESSIVENESS, LIFT, and LOBE SEPARATION ANGLE. An aggressive lobe opens and closes the valves FASTER, producing more vacuum and building cylinder pressure because, generally speaking, for a given .050" or .200" duration, the advertised duration is SHORTER. By comparing those numbers, you can get an idea of how AGGRESSIVE the lobe is. One cannot readily compare hydraulic and solid lifter cam advertised duration because the checking lift is different--- .006" for hydraulic and .015" or .020" for solid. The Comp Cams X/E cams are examples of aggressive cams. Additional lift for a given duration allows more charge into the cylinders without a loss of low end performance or idle characteristics. As long as your valvetrain geometry is correct, more lift is a win/win situation. Lobe separation angle has a direct affect on idle characteristics and the shape of the torque curve. Going tighter increases OVERLAP, the amount of time (in degrees) in which the valves are open simultaneously which leads to reversion (the unwanted reversal of air/fuel or exhaust past its respective valve). The benefit of a tighter LSA is a greater PEAK torque output and usually higher average numbers. The opposite is true for a wider LSA since the intake and exhaust won't tune to the same degree.--- less peak numbers but a broader curve. If you keep the duration numbers in check, then a tighter LSA will give a noticeable idle without losing low end. As a ballpark estimate, a ten degree increase in .050" duration numbers from stock is pretty good--- especially when an aggressive lobe is used. MORE TO COME..... QUESTIONS OR COMMENTS? E-MAIL ME @ PSPERFORMANCE@COMCAST.NET

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