letitsnow Posted January 28, 2009 Share Posted January 28, 2009 I'm interested in converting one of my smallblock cars to EFI, however there seems to be a lack of inexpensive manifolds that will feed a 400-450hp v8. After some searching around on the web I found this.(done by anesthes on thirdgen.org, to give proper credit) Everything I've read has said that there is not nearly as much torque loss with an EFI single plane than a carb'd single plane(due to fuel not falling out of suspension at low velocities) and that distribution is very good compared to intakes like the LT1 and TPI. I did some more reading and learned that he didn't use a plenum because of the blower, but that an N/A engine liked a plenum roughly 50% of the engine volume. I've also heard that elbows can cause unequal distribution at high velocities, biased toward the back of the elbow. I found this conversion that was done with some basic tools and employed a plenum, however I bet a box plenum isn't ideal. It's kind of sloppy, but not bad for hand tools. (done by Bjorn on TGO as well) I bought a used single plane intake off craigslist for $20. I have access to a machine shop and welder, so fabrication shouldn't be an issue. I'm curious about designing a relatively simple to build(welded together from mostly flat pieces would be good), that uses a stock LT1 TB and bolts to a squarebore holley intake manifold. Is the box a sound design when used like this? I'd like to angle and extend it towards the drives side so the TB inlet is almost above the power steering pump. Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 28, 2009 Share Posted January 28, 2009 I would be picturing AC ductworking.. make a plenum "box" but think diamonds. I am not the best ant being technical in descriptions like this, but imagine an airbox that has a bottom made from two traingles (front/rear) and two trapezoids (sides.) It would almost look like an awkward shaped house, except the "end caps" would slant towards the center of the house rather than be straight vertical. Overall, when you think of the volume of this "house" picture it a bit larger than you would want; I am going to cut some interior volume out of it later and you want the rough dimensions of this "house" large enough to accommodate it. So, take your house, chop the top of it off for your manifold flange, and flip it over; the roofline of the "house" is now flat and it looks more like a hopper. the manifold flange is now the bottom (not the "top.") Go to the top of the manifold, front driver's corner of the box, and cut the corner entirely off at a 45* angle, so you have a place to weld on your TB flange. Now, after doing that, you would have what I imagine is a "dead spot" in the upper corner opposite the TB flange, and indeed in both other top corners as well. If you could find a way to fill these corners out, and make the volume of the plenum more "egg shaped" and curved at any intersection, you would probably make it flow more naturally and evenly. Instead of packing in some aerosol foam and carving it out to desired shape, you might ALSO be able to simply profile the shape that you would want with some parallel "fins" in the corner, pointing towards the manifold inlet.. I am bascially picturing a series of walls in the corners to act as air baffles to keep airflow out of the "dead zones." I don't know how much of this concept is making it across, but its fun for me to imagine, so I hope you are getting some of it. Quote Link to comment Share on other sites More sharing options...
Xander Posted January 28, 2009 Share Posted January 28, 2009 professional products make a single plane efi intake. They also sell a fuelrail kit for this manifold. the fuel rail kit is rather good. It comes with a pressure regulator and all kinds of fittings. http://www.northernautoparts.com/ProductModelDetail.cfm?ProductModelId=17298 also over at thirdgen.org there is a separate forum on this subject. http://www.thirdgen.org/techboard/alternative-port-efi-intakes/ Quote Link to comment Share on other sites More sharing options...
letitsnow Posted January 28, 2009 Author Share Posted January 28, 2009 Buying something pre-made for it would ruin the fun:razz:, and it would significantly increase the price of this super low budget project. When you search for "plenum" at TGO, there are way more results for aftermarket intakes than converted single planes. I would be picturing AC ductworking.. make a plenum "box" but think diamonds. I am not the best ant being technical in descriptions like this, but imagine an airbox that has a bottom made from two traingles (front/rear) and two trapezoids (sides.) It would almost look like an awkward shaped house, except the "end caps" would slant towards the center of the house rather than be straight vertical. Overall, when you think of the volume of this "house" picture it a bit larger than you would want; I am going to cut some interior volume out of it later and you want the rough dimensions of this "house" large enough to accommodate it. So, take your house, chop the top of it off for your manifold flange, and flip it over; the roofline of the "house" is now flat and it looks more like a hopper. the manifold flange is now the bottom (not the "top.") Go to the top of the manifold, front driver's corner of the box, and cut the corner entirely off at a 45* angle, so you have a place to weld on your TB flange. Now, after doing that, you would have what I imagine is a "dead spot" in the upper corner opposite the TB flange, and indeed in both other top corners as well. If you could find a way to fill these corners out, and make the volume of the plenum more "egg shaped" and curved at any intersection, you would probably make it flow more naturally and evenly. Instead of packing in some aerosol foam and carving it out to desired shape, you might ALSO be able to simply profile the shape that you would want with some parallel "fins" in the corner, pointing towards the manifold inlet.. I am bascially picturing a series of walls in the corners to act as air baffles to keep airflow out of the "dead zones." I don't know how much of this concept is making it across, but its fun for me to imagine, so I hope you are getting some of it. I'm having a hard time with the shape you're describing. What I've got is a diamond shaped floor(when it's bolted to the manifold), trapezoidal sides, and a square front/back, and a roof that is the same shape as the floor but smaller. Do I have it upside down? Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 30, 2009 Share Posted January 30, 2009 I'm having a hard time with the shape you're describing. What I've got is a diamond shaped floor(when it's bolted to the manifold), trapezoidal sides, and a square front/back, and a roof that is the same shape as the floor but smaller. Do I have it upside down? Lemme try and draw it out in paintbrush.. I can throw together a sketch that should illustrate my points well enough. Here: The large arrow points towards the front of the car; the circled "dead spot" is the major one I was trying to talk about. For the image on the left, picture a V8 underneath, lokoing at the belts and water pump, and seeing the front of the two valve covers on either side of my plenum; for the pic on the right, imagine seeing the top of one valve cover in the foreground. Truncate one corner of your upside down house and put a TB flange there (that oval is supposed to represent a throttle body LOL) To eliminate the "dead spot" imagine what would happen if you took a large cardboard box, and held it so that only one bottom corner was in contact with the ground, filled that with foam, and then pushed a basketball down into the corner. the corner would be rounded on the inside after the foam cured and you pulled your basketball off of it. My whole "trapezoid/triangle" thing threw my description off.. is my idea easier to wrap your head around now? Quote Link to comment Share on other sites More sharing options...
letitsnow Posted January 30, 2009 Author Share Posted January 30, 2009 That makes pretty good sense now. I'll try making it out of cardboard when I get some time. What do you think about just cutting off the dead corner and putting a triangular plate over the resulting hole? Quote Link to comment Share on other sites More sharing options...
Daeron Posted February 1, 2009 Share Posted February 1, 2009 That makes pretty good sense now. I'll try making it out of cardboard when I get some time. What do you think about just cutting off the dead corner and putting a triangular plate over the resulting hole? Definitely sounds closer to "ideal" IMHO.. and far more practical than what I have thrown at you. (thats a problem of mine TBH ) Maybe a largish triangle for the main "dead corner" and two smallish ones on the other two? Honestly I wouldn't make them too much smaller even.. but when you start thinking about it the "other two" probably "should" be triangles with sides of uneven length, pointing primarily towards the TB inlet, and with the shortest side being the base of that triangle on the front passenger head side/rear driver firewall side of the original "house." (In other words, the "primary arrow" of the triangles would each point towards the TB flange, the "secondary arrow" would point towards the exit to the manifold, and the broadest, shallowest arrow would point back towards the firewall, or out along the firewall towards the passenger wheel.) The main "dead corner" I would say, make an isosceles triangle (two long equal sides, one shorter base) with the base on the top, and the point going down towards the exit to the manifold. I am trying to "blunt" the corners in a manner that is intuitive to the airflow.. but I am no expert by any means, I am just throwing ideas your way. I gladly welcome any critique or correction by anyone who has done this before. I have NO idea at what point the ideas I have might start becoming a wild goose chase (point of diminishing returns and all) but I think the ideas we've reached are a pretty good spot to shoot for with a first attempt. It is all easy to replicate with sheetmetal and a welder, its just a matter of mocking up the angles and lines... and it seems fairly workable. With nice looking welds, on, say aluminum sheet... it actually sounds downright pretty if you ask me Quote Link to comment Share on other sites More sharing options...
letitsnow Posted February 2, 2009 Author Share Posted February 2, 2009 Unfortunately, I don't have the equipment or skills to do aluminum, I was thinking about making it from steel and having it powdercoated. Quote Link to comment Share on other sites More sharing options...
Daeron Posted February 2, 2009 Share Posted February 2, 2009 That wrinkle finish stuff is rather nice as well. If black works on the LSx series, it can work for you too Quote Link to comment Share on other sites More sharing options...
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