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


SmileWavySmileWavySmileWavy

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.

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

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

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