Originally Posted by mr_tkidd
has anybody ever herd of Edelbrock 35283 - Edelbrock Pro-Flo XT EFI Systems
i have a caprice and i was job looking arround for some parts to incress my horses. pretty much im in the process of turning my stock 5.7 350 into a beast! i just wanted to know what this kit will do/capable of? and is it worth over 3k investment?
Year of Caprice would be really helpful. In general since the dawn of the SMOG era the 305 and 350 have really been hampered and hammered by extremely mild camshafts, low compression, poor performing combustion chambers, poor piston crown designs these last two adding up to very bad ineffective and inefficient combustion. This goes beyond port flow and valve sizes which can be improved but without a different combustion chamber and piston crown shape the resulting engine is always leaving big power numbers on the table and getting really crappy gas mileage doing it. So if you;ve got 3000 buckeroos burning a hole in your pocket forget the EFI or other addons at this point and aim for the heart of the matter:
- Pistons with decent crown shapes that means either flat tops but with unleaded regular more likely a piston that is half dished and half flat top. The flat top gets the squish/quench functions up which adds the equivalent of 4 to 8 octane values to the fuel you use. The dish lets you dial in the total chamber volume that keeps the compression from going beyond what the fuel and chamber can do to keep the detonation wolf from the door. the flat portion of the piston can be closed to about .040 inch of the matching portion of the head. As the piston goes over TDC it rams the mixture from the far side of the chamber to in-front of the spark-plug stirring the hell out of it and increasing the density in-front of the plug. This makes it easier to set on fire (fewer miss fires), burns it faster so the cylinder pressure is easier to optimize on piston position for best extraction of power, and it burns more completely so you get both the ponies you pay for and less emissions doing it without gadgets to clean the exhaust.
- The combustion chamber shape works with the piston in providing the optimum turbulence (squish) and heat sinking the potentially overheated end burn (quench). A small tight chamber keeps control of the incoming mixture giving it the proper amount of swirl and re-mixes the fuel which tends to get separated through the twists and turns of the intake system. To this end you want the L31 style Vortec head. This can be an aftermarket head with the so-called heart or kidney shaped combustion chamber. This type head will deliver from 20 to 60 more horsepower depending on the cam, the crazier the cam the more power you can expect. These are sometimes referred to as fast-burn heads either as a type or as a name. The high quality of squish/quench, lots of mixture swirl and the spark-plug being moved toward the center of the chamber all contribute to this feature which produces power, adds mileage, and cuts emissions.
- This leads kind of backwards into the camshaft which leads back into compression ratio which leads back into the head and piston selection. It is not hard to build a 400 horse 350 these days that uses a warm but certainly not a racing cam something along the lines of the Comp XE268H. Selecting the cam pushes on compression ratio. While most are familiar with the Static Compression Ratio (SCR) which is a determination from the volumes of the engine bore and stroke added to the volumes in the head, gasket and piston crown divided by the bore and stroke; there is another compression ratio called the Dynamic (DCR) that needs to be considered. The DCR spins off the piston's position as it rises up the bore before the intake valve closes. Until engine RPM builds sufficient mixture velocity in the ports to ram mixture into the cylinder against the reverse pumping forces of the rising piston the engine's size and compression ratio appear to be smaller than they measure and the engine looses power from about 3000 rpm down to idle, the wilder the cam the greater this loss which can be a lot. The solution is to raise the SCR until the DCR computes out between 8 through 9 to 1. 8 tending toward iron heads and lower octane fuel and 9 being aluminum heads and high octane fuel. Hitting in here increases bottom end power and overall fuel economy a lot.
All of this happens below whatever gets picked for an induction system. So start thinking about the guts and set the intake aside as if the guts are correct it really doesn't matter much what the intake is. I can make a 350 generate a solid 450-500 horses with a 2 barrel carb, so can you by picking the right guts to build on.