well that's where I'd start and redyno it after changes

 

The dynojets are ghey. If the carb is vacuum secondary, it's not going to load the engine up right, and chances are the secondaries aren't opening all the way, or at all. If that's the case, then that means the dyno tune will most likely be WAY off from the actual tune it needs to run best under a real load at the track. And even if the secondaries were opening all the way, carb'd cars don't always react well on dynos, most of the time they operate differently on a dyno than in real life, especially on dynojets. If you take it to the track it might be close or it might not, only way to tell is run it and shut down just after the traps, coast to a stop(off the track obviously) and pull the plugs and check them for proper fuel/timing. The RPM Air Gap is a great intake allt he way around, especially on a 347(it was actually designed a bit bigger than the standard RPM to give it bettering huffing when on strokers).

 

The Cobra intake is closer to the Edelbrock Performer Plus than anything else. It's good for a stock or mild build, but it's not going to handle your stroker very well. I doubt you'd pick up 30hp from just the intake, but you'd probably see a noticable overall improvement as well as more usable power at the top of the rpm range.

 

enlighten me here please. I always thought the dynojets are rolling drum dynos, where you have to accelerate the drum and therefore cause load (secondary should open then). what did I miss here?

Kalli

 

It's not the actual load the car will see. When you accelerate in a car the load is based on the rolling resistance of the tires, bearings in the drivetrain etc, the inertial load of rotating parts of the drivetrain like tires, gears, driveshaft etc, and most importantly overcoming the inertia of the car as you accelerate(ESPECIALLY from a dead stop). A rolling dyno just has drums of a given weight that you accelerate, and to call it a dyno is almost a misnomer, they're really an accelerometer. The vehicle accelerates the drums, and based on the rate of acceleration it tries to determine torque output. The resistance the engine sees accelerating that drum isn't even anything like what the vehicle really sees, and often the load is so minimal that in some cases it's closer to revving the engine in neutral than it is to driving it down a road. Even a Mustang dyno where you program in vehicle weight, gearing and all that other good stuff, is still only simulating what the car actually sees and there is room for error. Carburetors are extremely sensitive to HOW the engine is operating so they do even worse on a dyno, since the way fuel is metered and sheared is heavily dependant upon how the engine is operating and what the load is at a certain rpm.

At best a good dyno is nothing more than a tuning aide, it gives you a good baseline to go from and a safe starting point(on a carb'd car it basically MUST be a Mustang dyno to get close). Ultimately the final tune has to be dictated by driving the vehicle and adjusting for best performance. That's why if you look at even Formula 1 where they have multi million dollar dynos with TRANSMISSIONS, that load the engine and shift gears up and down and simulate running the engine in a car around a certain track, they STILL adjust the tune once the car is out on the track. The technology in dynos like everything, isn't perfect, and requires bit of fine tuning beyond the dyno in the actual driving condition. That's why many people, especially those with carbs will get a race car dyno tuned after they have it set up, only to find it picked up power on the dyno, but got slightly slower on the track.

 

thanks a millionj for that ex-planation. makes sense to me !
just never thought you could be so much off with for exampl ethe vac secondaries/load

 

^^^^^^In the end all that matters is ET.........I wouldn't get depressed or excited about big or little numbers..I've seen cars with smaller numbers whoop up on ones with larger numbers

 

Yeah, who cares about peak power output, maximize power under the curve and tune at the track and it'll run quicker than most people think it should.