View Full Version : Port and Polish Questions???

07-20-2004, 09:58 AM
I'm thinking of getting my Intake manifold ported and polished. Now my buddy works at a machine shop and he told me its a handheld procedure and that anyone would overcharge for the work to be done. I'm kinda hesitant on doing this myself or asking my buddy to do this. I'm not sure how many milimetres to bore out or where to get the carbite dremel bits.

Has anybody done this, or know anywhere i can find more info on it.

07-20-2004, 12:29 PM
if u want... u can ask burnhard22 what he did for his port and polish... he did that to his e30 88 325is turbo... he's also my bro... :P... ask him about it... he might be able to help u out...


07-20-2004, 12:44 PM
porting is a real science that can be easily screw up any sort of performance gain if not done properly. I recommend taking it to an experienced engine shop before attempting it yourself. Gains are very minimal and are only felt when the rest of the motor is completely tuned properly.

Polishing the intake can be done yourself with patients... again, HP gains are minimal. Below is a link of the intake ports from my old 3.2L... they were ported, knife edged, polished and flow benched. Cost me around $1000.00 in labour to have it done.


07-20-2004, 07:26 PM
You can definately port match your m20 intake manifold yourself. It's not very hard. Carbite bits are not required.

The manifold is made of a rather soft cast aluminum, and it will load up most bits fairly quickly. I used a dremel and a rasp bit. Cut on a slow speed, if you turn the dremel up to max the aluminum will get hot and load the fit up very fast.

Actually porting the manifold cannot be done yourself, you will have to send it off to Extrune Hone to get it done.

Here is a before and after picture of the ports. The green dye shows the actual size of the gasket and the ports on the head. In the picture the "after" port wasn't done. I did go back and flare the fillet back in alot further with a larger bit.


As you can see there are alot of casting "steps" and texture that are removed.

07-21-2004, 01:31 AM
So What is the amount of hp gain am i looking at? Randy says "Gains are very minimal and are only felt when the rest of the motor is completely tuned properly. " And there's no way i'm paying over a 1000 to have someone do this, no offence but i just don't have the cash. I'm a reaaaly handy guy don't get me wrong this is not outta my power i just wanna have all the information before i begin this procedure.

07-21-2004, 06:48 PM
I can't put a number on the gains for you.

Are there gains to be had? absolutely.

Will I make up some imaginary number like some of the Pepboy tuners on these boards? No.

Just do the work as I described above and be done with it. Its not hard, doesnt take too long, and will definately make a difference in conjunction with a ported head.

07-22-2004, 11:06 AM
Thanks Jordan, Your help is straight forward and appreciated. By the way nice car, i like the stock look and am doing a plastic bumper conversion for my 88 325is.

The Sly
07-22-2004, 02:34 PM
I have done all of my porting and polishing ..

A good reference guide was the site from Metric Mechanics...

They actually show where to port and polish for best results...