Mopar Action On-line – Tech Questions
don duick, sydney, NSW, australia, 1970 Dodge Charger 440
I put Edelbrock heads on my new 440. It has 10.25:1 compression, 224/230 (@ 0.050″) cam, Weiand dual plane inlet manifold, inlet and a Holley 750 HP carb. I have HP manifolds and I also have Hedman headers with 1 ¾ ” primaries, 3″ collectors, twin 2 ½ ” exhaust. Which one of these two exhausts would you recommend? My worry is that I would not get full benefit from these heads with the HP manifolds. This car is mainly used as a weekend cruiser, no future mods are planned.
Love reading your replies on this site.
As airflow (and, therefore, HP) increases, the iron manifolds become more and more of a “cork”. When the factory built big-blocks over 400 HP, they went to special manifolds (Max Wedge, etc.).
Headers — any headers — will be a huge HP gain. Of course, headers as small as the ones you chose will offer the least gain, but the gain is still significant, as a wild guess: 30HP. That number might increase to 50-plus with larger primary pipes. The rest of the system is also marginal, 3″ would have been better. Just as a point of reference, late model 6.1 and 6.4L SRT cars are 2.75″.
Of course, that dual plane manifold is also a cork!