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Registered
Join Date: Jan 2006
Posts: 195
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3.2 intake manifold
Hello guys,
Today I was see that the inside of the intake manifold of my 88 3.2 engine is a bit rough.If I remove all imperfections (not much) and I have it polished is there even a tiny increase in HP and/or throttle response ? Of course I don't like to increase it's diameter size. Thank you, Jim 
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02-07-2008, 09:50 AM
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Registered
Join Date: Nov 2000
Location: Dallas
Posts: 3,578
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Not sure but I have heard that it's better to have the interior surface of intake manifolds be slightly rough as that helps improve airflow. Apparently the most effective improvement to the Carrera intake manifold is to make sure all 6 tubes/runners FLOW evenly. This is not something that's easy to monitor for the average do it yourself owner.
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Buck '88 Coupe, '87 Cab, '88 535i sold, '19 GLC 300 DD Warren Hall, gone but not forgotten |
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02-07-2008, 12:51 PM
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abit off center
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If your only moving air as in an injected engine then you can polish them but if its a fuel/air mixture as in a carbed engine you want a honed or sanded finish on the intake, this lets the mixture coat the manifold walls (boundry layer) which moves much slower than the rest of the mixture and acts like a ball bearing surface which helps move the rest of the mixture thru the intake system, especially at low speeds. A polished surface with carbs will not allow this boundry layer and can cause the fuel to dropout at lower RPM's
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______________________ Craig G2Performance Twinplug, head work, case savers, rockers arms, etc. |
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02-07-2008, 06:22 PM
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E-85 sippin drunk
Join Date: Jan 2002
Location: Warner Robins, GA
Posts: 1,554
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Craig.. your information is spot on.... but the 88 3.2L intake is on a F.I. motor....
Jim, You will never get every runner even close to exact unless you cut the manifold apart, do your sanding and polishing, and then reweld back together..... IMHO... the best solution is to get the manifold Extrudehoned... It will cost about 600 US dollars.... and is worth it.... but only after you have done just about everything else that you can to your motor first. I would not waste the money on a motor that does not have an aggressive cam, aftermarket headers, forced induction, etc.... Most of the gains come from having the runners more equally balanced to each other.... rather than enlarging them. Air flows like water....taking the path of least resistance. Extrudehone uses an abrasive media to mimic the flow of water...and only taking out a little metal where there is a restriction.... and then smoothing out the rest of the part... look them up...... http://www.extrudehone.com/auto/auto-performance.php
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Brad...930 gt-1 racecar, increased displacement to 3.6L, JB racing Cylinders, JE 8 to1 pistons, stroked crank, Carrillo rods, extrudehoned 3.2L intake, full bay Bell I/C, GT-2 EVO cams, Rarly8 headers, GTX-3584RS turbo, twin plug, P&P heads, Link G4 EFi system, G-50/50 with LTD slip and oil squirters/oil cooler, zork tube, full race coilover system, with carbon fiber body, full cage, E-85 sippin drunk |
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02-08-2008, 06:18 PM
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Registered
Join Date: Jan 2006
Posts: 195
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I remove all imperfections with 80 grit then smooth with 120 and with 150 as final pass.
I use a custom made extension to my electric drill to port the runner up to where the curves started.I also polish the main intakes tubes with 80 and 120 grit here. It looks a million times better now... Thank you all for your help! Jim |
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02-29-2008, 08:38 AM
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1969 and 1986 Porsche Targa and Coupe 1720cc and 3
