a stock 305 which would be better for performance a single plane or dual plane? whats the difference between them? thanks

 

Dual. There really isnt even a debate here between the two.

 

Dual for sure. The dual plane splits 4 cylinders per level. The single has all plenums connected to a common area under the carb. Dual works better with lower RPM, single with higher...then you have the smaller displacement of the 305...go dual.

 

http://forum.grumpysperformance.com/...hp?f=55&t=5510
read thru this and its sub links

 

What kind of performance increase ( in hp and torque) can be expected for a stock L69 305 with a dual plane intake?

Thanks!

Chuck

 

A totally stock 305 as you know is rather pathetic in both head flow and cam timing and most have restrictive exhaust. that doesn,t mean the engines hopeless , only that you need to think thru your choices carefully, Ive normally seen better results when both the intake and cam are upgraded, a common combo of well matched parts for a 305 is
http://www.summitracing.com/parts/CMB-03-0113/
http://www.cranecams.com/product/car...detail&p=23759
THESE HEADS WOULD REALLY HELP
http://www.summitracing.com/parts/TFS-30300001/
the combo of intake and cam alone, is usually worth about 30-35 hp, which is a darn nice gain, the intake alone is probably worth 10-15hp, but its going to be worth more as the cam and heads are upgraded to flow more also, because its not nearly as restrictive as the stock intake.
the heads plus intake and cam should easily be worth 50-60hp minimum. but before you go throwing cash into a 307 you might just want to save up and build a 383-406 SBC that has more potential.


these links and sub links should help
http://forum.grumpysperformance.com/...uilding#p18253

http://forum.grumpysperformance.com/...php?f=69&t=519

http://forum.grumpysperformance.com/....php?f=55&t=58

http://www.airflowresearch.com/artic...le115/A-P1.htm

 

Definetly a balancing act between cost/performance issues when dealing with the 305. Thanks for the info!

Chuck

 

The OE intake manifold is a dual plane. The dual plane intake divides the runners into 1/2 long, 1/2 short to extend the engine's torque curve. The dual plane design favors low and mid range torque production. Most DPs are designed for engines making peak power below 5,500. Some performance versions like the Performer RPM have been optimized to support power up to 6,500rpm.

As a general rule, you want to use a dual plane intake for any engine that makes peak power below 6,000rpm and is used mainly on the street. The single plane manifold is for an engine that makes peak power above 6,000rpm and where a long flat torque curve with optimal high RPM horse power power is the goal. Keep in mind that in most high performance engine builds, a performance dual plane intake will produce better average torque than a single plane even though it may reduce peak power slightly.