Originally Posted by pjc360
I am running true dual exhaust on a 300 hp crate 360 magnum in a 91 dodge truck the pipe diameter is 2 1/4 and i have an H pipe that is also 2 1/4 and aout a foot long, for mufflers i have 18 inch flo-pro glass packs that have a louvered inside core. But these glass packs did not have any inlets or outlets, we welded our own inlets and outlet on them and they have a 3 inch inside diameter.
I have been told louvered glasspacks are restrictive... But i was thinking since these glasspacks i have dont neck down inside that they'd most likely flow pretty well considering they have a 3 inch inside diameter.
I mean i looked inside these glasspacks before i bought them and they were huge inside 3 inches and they didnt neck down at all becuse they didnt have any inlets or outlets on them we welded on our own wich were 2.5 inches so my exhaust pipe never runs into anything smaller, it only runs into bigger.
So thought i'd ask if this system should give sufficient enough exhaust flow i also have 1 5/8 hedman llong tube hedders. Just wanna make sure i am not choking my engine, there isnt any big bends in my exhaust, for the most part its stright thru exhaust.
'Packs having louvers- or anything, actually- that protrudes into the flow path of the exhaust, or cores having irregular, rough openings like those w/saw cuts the length of the core are going to be more restrictive than a muffler having smooth, non protruding openings in the core. As you surmise, the saving grace is the 3" ID- which will compensate for the protruding louvers to a large degree. But they'll still not flow as well as they would w/o louvers; the protrusions still will cause some turbulence.
2-1/4" exhaust pipes are the minimum
I'd use. IMO 2-1/2 would be a better size; 3" pipes would be overkill unless you had a lot of length and/or sharp bends or a lot of bends of any degree.
I like the use of a connector pipe between the sides, too. There is an optimum place for the connector, but for vehicles w/a full exhaust system, placement isn't super critical as long as the connector is aft of the collector and before the mufflers. I would choose to put it close to the collectors unless there's a fitment problem. That way there will be a sharing between the two sides that much sooner, which could help reduce backpressure when using a relatively small pipe diameter.
But all things considered, you should be fine w/the set up the way it is. Maybe not optimum, but still OK.