a6t8vw Posted September 15, 2006 Share Posted September 15, 2006 I just about got my motor swap finished. I have long tube headers with 3" collectors on my chevy 350. How do you think a single 3" compares to dual 2.5" system? more low end? also doesnt a single 3" pipe flow more than 2 2.5" pipes? check it out http://www.cardomain.com/ride/2314369 Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted September 15, 2006 Share Posted September 15, 2006 go w/ the dual 2.5" and add an H or X pipe towards the beginning of it. 2 of the 2.5" is gonna flow more cuz the other way you'd be cramming (2) 3" pipes into (1) 3" pipe. The other way you'd have each pipe just stepping down from a 3" collector to a 2.5" piping, but each header would still be breathing out on it's own and not having to share 1 pipe w/ the forcing of gasses into 1 pipe. Plus it'd look and sound a lot better w/ a dual imho. very clean z though! we might have to meet up sometime and get a few Z's together for a meet or a cruise of some sort. Quote Link to comment Share on other sites More sharing options...
Bartman Posted September 15, 2006 Share Posted September 15, 2006 I went with dual 2.5". but I would run an 'x' pipe instead of an 'h' pipe. An 'x' pipe should allow you to take advantage of the scavanging effect to increase your performance. You will find a great deal of discussion on this issue with varying opinions. Quote Link to comment Share on other sites More sharing options...
NCchris Posted September 15, 2006 Share Posted September 15, 2006 Dude, very nice swap! If mine turns out half as good as yours, I'll be extatic! Who's long headers did you use? What car were they for and how much work was involved to get them installed? TIA chris Quote Link to comment Share on other sites More sharing options...
John Scott Posted September 15, 2006 Share Posted September 15, 2006 Again you'll hear both sides. I like the sound of the single, not as blubbery. A well designed three inch single can support well into the 400 whp from a V8 and is lighter than the dual. I'd bet you won't gain more than a few hp running the dual..if any. We have guys on this site running nearly identical stroker engine combos singl/ and dual with nil difference in 1/4 perf. But, I'm still scratching my head how Z-gad puts 600+ whp through his 3". BTW beautiful car! Quote Link to comment Share on other sites More sharing options...
dustin280zx Posted October 5, 2006 Share Posted October 5, 2006 either in hot rod or the chp mag they did a test on x pipes, h pipes, and open headers.the x pipe made alittle more power then open headers and the h pipe got the lowest hp on the dyno. The engine was a sbc but i forget what ci because it was along time ago since i read it. just alittle info Quote Link to comment Share on other sites More sharing options...
v8dats Posted October 5, 2006 Share Posted October 5, 2006 i like the duals to a single myself. lighter, sounds smoother,less drone. how did u fit those wheels? coilovers? spacers?? thanks Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 5, 2006 Share Posted October 5, 2006 Duals!!! Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted October 6, 2006 Administrators Share Posted October 6, 2006 lighter, sounds smoother,less drone. Not sure how you came up with lighter. Dual 2.5's are nearly 70% heavier than a single 3.0.... however, they would flow roughly 30% more. Quote Link to comment Share on other sites More sharing options...
a6t8vw Posted October 6, 2006 Author Share Posted October 6, 2006 how did u fit those wheels? coilovers? spacers??thanks yeah i made my own adapters front 35mm rear 25mm.. the wheels are offset +38 rear tire is 265/35 its about 1/4" from the spring perch so i would say im maxed out without going to coil overs... i know i can run a 295 on that rim and would like to so coil-overs are in the works andy Quote Link to comment Share on other sites More sharing options...
Phantom Posted October 6, 2006 Share Posted October 6, 2006 I've run both with my LS1 - duals to a Y pipe and then single the rest of the way out and now true duals with an X pipe all the way to a single muffler. Bottom line - even though they have more surface friction area 2.5 x 3.14 x 2 = 15.7" vs the 3 x 3.14 = 9.42" of the 3" pipe the dual 2 1/2" pipes have 2.5 x 2.5 x 3.14 /4 x 2 = 9.81 square inches of flow area vs 7.06 square inches for the single 3". Thats just under 40% more flow area which is huge. The single 3" is also harder to bend around and is more likely to bottom out than the 2 1/2". Breathing is the name of the game and dual 2 1/2" will give you more than a single 3". Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 6, 2006 Share Posted October 6, 2006 If you're worried about ground clearance but need max flow, why not consider dual oval pipes both with effectively 3 inch diameter? Quote Link to comment Share on other sites More sharing options...
John Scott Posted October 6, 2006 Share Posted October 6, 2006 I've run both with my LS1 - duals to a Y pipe and then single the rest of the way out and now true duals with an X pipe all the way to a single muffler. Bottom line - even though they have more surface friction area 2.5 x 3.14 x 2 = 15.7" vs the 3 x 3.14 = 9.42" of the 3" pipe the dual 2 1/2" pipes have 2.5 x 2.5 x 3.14 /4 x 2 = 9.81 square inches of flow area vs 7.06 square inches for the single 3". Thats just under 40% more flow area which is huge. The single 3" is also harder to bend around and is more likely to bottom out than the 2 1/2". Breathing is the name of the game and dual 2 1/2" will give you more than a single 3". You'll have to be pushing way more power to see any difference. Probably any gains on a 3-400hp V8 are going to be lost due to your car being heavier. At the differential 5.75" clearance under my 3". Unless I'm off road, not an issue. Duals look cool, personal choice..if its all about flow then why not dual 3"s? hope someone doesn't mind my showing their exhaust Quote Link to comment Share on other sites More sharing options...
a6t8vw Posted October 7, 2006 Author Share Posted October 7, 2006 about ready for some new tires there john? haha rad Quote Link to comment Share on other sites More sharing options...
John Scott Posted October 7, 2006 Share Posted October 7, 2006 about ready for some new tires there john? haha rad um,..not mine...Actually siliconboy's TT 383.. which can justify the use of dual 3". Quote Link to comment Share on other sites More sharing options...
lt1will620 Posted October 15, 2006 Share Posted October 15, 2006 hmm. interesting, So you all know, a single 3 inch will outflow a dual 2.5 inch system, yes the dual 2.5 inch system has a larger flow area, but the added surface area of the inside of a dual 2.5 inch system means much more surface area friction. that being the case, a single 3" WILL make more power than a dual 2.5. I saw almost 10rwhp on my LT1 camaro (stock motor) when going from dual 2.5 inch with single chamber flowmasters dumped before the rear axle, to a single 3 inch flowmaster cat back with a 3 chamber muffler. Quote Link to comment Share on other sites More sharing options...
v8dats Posted October 18, 2006 Share Posted October 18, 2006 Not sure how you came up with lighter. Dual 2.5's are nearly 70% heavier than a single 3.0.... however, they would flow roughly 30% more. what i meant was duals going into a single (with a Y pipe). thanks tho Quote Link to comment Share on other sites More sharing options...
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