jonlabree Posted June 13, 2006 Share Posted June 13, 2006 A while back I posted a note about how I had ported my exhaush headers and removed the stock blockage in the outlet pipe.Well, I finally got them put back on the engine and belive it or not ithas made quite a large difference in performance. It also has given my exhaust system and totally different sound. (with a stock muffler) A much mellowersound, but not loud.If you remember I ported each cylinder pipe and then because they are weldedon the inside, I had them rewelded all around the outside of each pipe. (theoutside is only spot welded) Then I had them sand blasted and coated them withPore12 black. and the heatsheilds with Pore12 silver. Looks, sounds, and performs much better much better. Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted June 13, 2006 Share Posted June 13, 2006 I have heard of this before. Where is this restriction located again? Link to comment Share on other sites More sharing options...
jonlabree Posted June 13, 2006 Author Share Posted June 13, 2006 In the outlet pipe right above the o2 sensor. Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted June 13, 2006 Share Posted June 13, 2006 Via the Pants Dyno, you know about how much there is to be gained? Link to comment Share on other sites More sharing options...
jonlabree Posted June 13, 2006 Author Share Posted June 13, 2006 Unknown, but I do notice a marked difference. <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> Link to comment Share on other sites More sharing options...
Barney Eaton Posted June 14, 2006 Share Posted June 14, 2006 This was covered in the last Reatta newsletter.Some time back, 2seater did not think you would notice an improvement on a stock engine. Good to hear you can feel the improvement. I enlarged a photo of the restriction and tried to calculate the area of the restriction and it was more than 25% of the inside diameter of the pipe. Link to comment Share on other sites More sharing options...
jonlabree Posted June 14, 2006 Author Share Posted June 14, 2006 Barney, I not only removed the restriction but I ported the headers at the cylinder head. Link to comment Share on other sites More sharing options...
Guest Greg Ross Posted June 14, 2006 Share Posted June 14, 2006 <div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> tried to calculate the area of the restriction and it was more than 25% of the inside diameter of the pipe. </div></div>I went thru this rationalization when considering switching to a 2-1/2" diameter exhaust system (a la '91 retatta) Calculate that area differential and although we're only talking an increase of 1/4" on the diameter, it represents an increase of something over 30% on the cross sectioal area.From memory, that photo that Padgett posted way back I'd take a wild guess and say you're probably doubling the available cross section, eliminating power robbing back pressure and causing heat build-up. All bad! Link to comment Share on other sites More sharing options...
2seater Posted June 15, 2006 Share Posted June 15, 2006 As Padgett has pointed out in the past, probably the only reason the rear manifold is as short as it is is for engine installation. The engine and cradle is installed at the factory from the bottom so it does make sense. While not curing the basic design, opening up that restriction is right at the point where the exhaust from #4 and #6 run right into #6 and the stuff coming from the front. This whole area could be improved with some additional fabrication (the front is already pretty good), but opening up what is already available costs almost zero dollars. I am not so sure about porting the openings at the heads, the openings are already larger than the ports in the heads. They are not welded very smoothly, and cleaning up the big bumps that may hang out in the exhaust flow, can be beneficial. If you can figure out how to remove the stubs of the individual header tubes from inside the "log" part will also help, but the only way I have found to do so is cut the manifold open, clean it out, and weld it back together without adding your own restriction. Link to comment Share on other sites More sharing options...
Guest maybe2fast Posted June 18, 2006 Share Posted June 18, 2006 quick question. I removed as much of the restriction as possible the other day at my shop and it did seem to make a difference. my 2.5 catless performance exhaust got alittle difference tone and felt slightly quicker. now I really don't want to remove the rear header from the car and I have a front manifold ready to install that I ported. Would it be bad to install just the front ported manifold and leave the rear one alone with the restriction removed? Link to comment Share on other sites More sharing options...
Guest imported_barra Posted June 18, 2006 Share Posted June 18, 2006 Has there been any change in the miles per gallon? Link to comment Share on other sites More sharing options...
Guest maybe2fast Posted June 18, 2006 Share Posted June 18, 2006 not sure... its hard to fill up these days Link to comment Share on other sites More sharing options...
jonlabree Posted June 18, 2006 Author Share Posted June 18, 2006 First let me say to Maybe2fast, I don't think it would hurt anything to only install the front manifold. I did the same thing for abut a week until I had time to change the back one.As far as milage, all I can tell you is that about three weeks ago I drove from Chicago to Milwaukke and back in heavy traffic on the tollway and averaged 25mph. Which I think is an improvement. <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> Link to comment Share on other sites More sharing options...
Guest maybe2fast Posted June 20, 2006 Share Posted June 20, 2006 consider that done! Link to comment Share on other sites More sharing options...
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