7MGFORCE Posted August 17, 2009 Share Posted August 17, 2009 Sbc 302 For 300whp will I loose power allover the powerband? I'm planning on running 2.5" the a ypipe that exit to 3". I would do dual but I have stock tank. Anyways any ideas? Quote Link to comment Share on other sites More sharing options...
Scarab 155 Posted August 17, 2009 Share Posted August 17, 2009 You could always make a Scarab type true dual system. It will clear the stock tank easily. Both pipes exit out the same opening (enlarged) as the stock Z system. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 17, 2009 Share Posted August 17, 2009 If the single exhaust is designed properly with a good merge collector and either 3" or 3.5" tube then you'll probably gain power over the dual exhaust. Why don't you do some dyno tests with before and after comparisons and let us know? Quote Link to comment Share on other sites More sharing options...
Iceman Posted August 17, 2009 Share Posted August 17, 2009 If I go V8, this is probably going to be my exhaust choice too. I am planning on getting an in-line exhaust dump valve so I can pull a cable and bypass the muffler and dump down. A good option is these oval pipes I have seen before. Gives you really good flow without getting too close to the ground. Quote Link to comment Share on other sites More sharing options...
7MGFORCE Posted August 17, 2009 Author Share Posted August 17, 2009 If the single exhaust is designed properly with a good merge collector and either 3" or 3.5" tube then you'll probably gain power over the dual exhaust. Why don't you do some dyno tests with before and after comparisons and let us know? Unfortunately I don't have niether in mycar so I'm trying to decide wich one I should go with I'm currently looking at magma flow or flowmaster y merge pipe. Which is better design? Quote Link to comment Share on other sites More sharing options...
johnc Posted August 17, 2009 Share Posted August 17, 2009 I don't know. I use merge collectors built to spec by SPD. http://www.spdexhaust.com/pdfs/02-11_Merge_Collectors.pdf Quote Link to comment Share on other sites More sharing options...
rustorbust Posted August 18, 2009 Share Posted August 18, 2009 This is how i just recently did mine, block huggers, 2.5" to the cheap summit merge to a 3" single..... Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 18, 2009 Share Posted August 18, 2009 years ago.... when did my first v8 conversion (350 chevy with a T5 trans), I used 2-1/4 duals off block huggers then to a 2-1/2 single (crushed bent) then ending with a turbo style muffler. Back then my 240 ran high 12's at 110mph. If you go by pipe ID area then 3 inch (6.488 square inches) is about equal to two 2-1/4 pipes (7.08 square inches). So just run dual 2-1/4 pipes to a 3 inch single but make sure to use mandrel bent pipe at the rear. I doubt you will loose much hp with a single 3. Especially if you use a high flow muffler and mandrel bend pipes in the rear. I built a system like this on a friends V8 conversion and it had huge resonances/droning issues. I ended up adding a H-pipe after the transmissions and installing 2 dynomax bullets in the dual section of the exhaust (right before the Y-pipe). Really made a big difference. Car went from undriveable to sounding almost stock when driving slow. Quote Link to comment Share on other sites More sharing options...
7MGFORCE Posted August 20, 2009 Author Share Posted August 20, 2009 Johnc you mention properly designed and it seems that the more I look into it distance from headers does come up. But I can't find the specific distance from the header flange on the head before a y is inroduced. Any pointers? And is the perfomance difference minimal from optimum to off by a foot or so? Quote Link to comment Share on other sites More sharing options...
johnc Posted August 20, 2009 Share Posted August 20, 2009 28 to 32" is typical from the back of the exhaust valve to the last merge for the cylinder displacements we're working with. If you have to miss the length for packaging reasons, longer is better but try keep it with 10% of the range above. Quote Link to comment Share on other sites More sharing options...
7MGFORCE Posted August 20, 2009 Author Share Posted August 20, 2009 Sorry I'm alittle confused. When you say from the back did you mean the distance when measured the exhaust only in horizontal? Or is the header lenght included in that measurement? What I mean is let say our aim is 30" and the headers measure 12" from head to headers flange, that will leave us with 18" right? And that 18" including the merge/y pipe correct? Basically the measurement ends when the y turns 3"? Did I understand you correcly? Thanks Quote Link to comment Share on other sites More sharing options...
johnc Posted August 21, 2009 Share Posted August 21, 2009 The length measurement is fron the back of the exhuast valve and includes the exhaust port length, header primaries, secondary y pipes, etc. When you hit 3" all merged together you should be 28 to 32" from the back of the exhaust valve. Quote Link to comment Share on other sites More sharing options...
7MGFORCE Posted August 21, 2009 Author Share Posted August 21, 2009 Oh okay so it's not just from the headers flange but from the exhaust valve itself. Thanks a lot Quote Link to comment Share on other sites More sharing options...
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