Performer rpm vs SD

[flyinlow]

I understand the dual plane rpm intake produces peak power sooner then the single plane SD.  Why?

[firefighter3931]

I understand the dual plane rpm intake produces peak power sooner then the single plane SD.  Why?

The answer is complicated but it boils down to runner design. In a nutshell, the dual plane is more restrictive so it creates a stronger vacuum signal at lower engine speeds. Each cylinder is seeing only 1/2 of the carburator with the reduced plenum size of the dual plane (divided center). A single plane using an open plenum has all 8 cylinders seeing all 4 venturies of the carb so the (vac) signal is weaker down low. It's a matter of airflow restriction in the design of the manifold that "tunes" the engine for specific rpm ranges.

That's my semi educated explanation >  

Here's a good read on intake manifold design : http://victorylibrary.com/mopar/intake-tech-c.htm#new




Ron

[flyinlow]

Thanks Ron 

I will have to read that a couple times.

I got a NOS Thermoquad on ebay. I wanted to take the RPM intake / performer 800 off and try the Street Dominator with the new TQ with a 4 hole spacer. That article talked about a single plane with a divider. Wonder if you can make a plate with a partial divider to install under the carb.

I was suprised that the Individual runner /carb did so well across the board.

[elacruze]

Back in the day (I hate that phrase but it works) when Holley Strip Dominators and Edelbrock Torkers ruled, it was pretty common on smaller engines to make a carb spacer plate with a plenum divider hanging from it. The closer to the plenum floor the divider was, the better the bottom end was. I was never convinced that this was a better solution than a smaller carburetor, usually it was the guys trying to force a 355" small block Chevy to swallow an 850 holley DP.

Eric