I was going comment on the sbc thread but this is more relevant and needs it's own thread. Those Hedman 66609 in the sbc thread are more a mid length header in my books. Yeah tests show around 10 hp less on 300 HP motors vs long tube headers. My Sanderson shorty headers for my Olds V8 are basically 1 5/8" tubular manifolds with a 3" collector. I needed custom down pipes but I could route everything through the passenger side hump. The new Thornton manifolds are the same with either 2.25" or 2.5" outlets and take A body down pipes. I am not super impressed with the larger 1 7/8" primary tube/ 2.5" outlet version for an extra $250 with how they squashed the one pipe. There was room to move that pipe tight against the next pipe, allowing less flattening. It would made the flow loss minimal. I know full length headers can be flattened but much less realistate and right near the outlet can't be good. I assume some tweaking is needed in a G body using A body down pipes. The Pypes down pipes tend to not even fit A bodies let alone G bodies. The Olds Hedman shorties are also mid length but go nearly straight down, the sbc sweep back, making ground clearance tight on the Olds, you need a tight radius bend even on A bodies. They do fit G bodies even though they say only earlier cars. I assume bolt on down pipes are available for popular sbc shorty headers with larger collectors, we have squat. The BBO is another can of worms. The W/Z manifolds give up 30 HP over long tubes. The new Thornton shorties for the BBO are super nice but not sure how the fit is in a G body. The Hooker headers limit turning radius and the expensive DMR and American Racing headers are cost prohibitive. Thoughts and personal experiences welcome.
