MaSnaka John A back pressure test is done with a piece of hose( orange ) hi temp and a 0-15 psi pressure gauge. The Tool guys sell them for about $40.00. You need to have a bung welded into the side pipe for the port to get the reading. I have FI in my car so I just remove the O2 sensor. Witout getting into the story world, depending on who make the side pipes for your car, there is a 10-40HP loss in the higher rpms. If you have the bung welded into the side pipe You can test the system with a road test and watch the gauge. Exhaust systems are like head porting, there is some (BLACK MAGIC) to getting the most performance out of the motor with the smallest power loss to the motor at all rpm ranges. At WOT you want to see between a 1.5- 3.0+ pressure reading. Anything more and the exhaust is restricting the motor for power, having not enough backpressure, Open headers and you have the same thing with a possiblity of burning out the exhaust valves. The question is trading noise and power for HEARING.
My ERA pipes work nice for street driving. This is what they where built to do. They do kill some HP in the higher RPM with my 452 now 482 motor. I don't have a dyno run with before and after side pipe switch, to race pipes. I will say that you can't drive the car long without ear plugs with these pipes (race) and not have cops hear you a mile away. Neighbors are not happy when I fire this car up either. Race track no problem, quiet development PROBLEM.
It's a simple test minus the bung hole welding. Hope this helps point you in the right direction. As far as the build up IMO the parts you have are matched for the 1,500 to 4,500 rpm range. There is something wrong with the air cleaner. Mythinking is that there is no space between the top of it and the carb. I think that the choke butterfly is being pushed down with the top on and screwing up the flow of air to the carb. Quick test with the cair cleaner top on. wipe some grease on the under side of the air cleaner top and install it on the carb WITH the choke plate in the full open position. If you see any grease on the choke plate, see if you have an interferance problem with the lid. If yes or 1/4" of clearance, All the dyno readings are no good and need to be redone.
I run a small 8" cal custom chrome air filter on my throttlebody setup and in my case I got 6 more HP because of the air bending into the throttlebody. A carb is another story but have good clearance inside for the choke plate on a holley carb. Grease the lid, see if it hits, then run a straight piece of something over the carb and tell us how much clearance there is between the choke plate and the flat piece. See if the choke hits the flat stock. Get back to us.
Lets fix the carb issue first before getting into other modifications to the motor
Rick L.
Back Pressure test
Threaded Mode
