Author Topic: head porting & polishing (Read 6405 times)

Selfish · « **on:** February 27, 2009, 02:50:49 PM »

hi everyone. I'm about to tackle the task of replacing the head gasket on my 91, 318i, because I really miss driving it. I was wondering if anybody has done any head polishing and porting (or any other task that I should do while I'm at it, for that matter) and if so, is it a complicated process? I've seen some guys do it on youtube and it doesn't look hard at all. In fact, I'm more concerned about messing up when putting everything together after replacing the head gasket. I was going to have someone more experienced help me out, but the guy is always too busy for me, like he was going to do it for free....so I said f** it, I'll do it myself. All input or comments welcome.

xwill112x · « **Reply #1 on:** February 28, 2009, 08:55:23 AM »

I've ported and polished the heads on a 91' 5.0 mustang, but not on a m42, it really isn't tht hard.

and since your a local, i'll help ya out...some

http://lmgtfy.com/?q=how+to+port+and+polish+a+cylinder+head

cheers

Selfish · « **Reply #2 on:** February 28, 2009, 11:31:00 PM »

I also read in a blog somewhere that you can adjust (advance) the intake cam to get some extra top end horsepower, without having to buy adjustable cam sprockets, since (supposedly) M42 engines already have them tunable cam sprockets from the factory. Is this right?

Danny707 · « **Reply #3 on:** March 01, 2009, 12:32:53 AM »

Not worth it.

xwill112x · « **Reply #4 on:** March 01, 2009, 01:07:52 AM »

Quote from: Selfish;67399

I also read in a blog somewhere that you can adjust (advance) the intake cam to get some extra top end horsepower, without having to buy adjustable cam sprockets, since (supposedly) M42 engines already have them tunable cam sprockets from the factory. Is this right?

yes, but best setting is factory.

marko · « **Reply #5 on:** March 03, 2009, 01:06:24 PM »

unless you trully know wtf you are doing - do yurself a HUGE favor & do NOT port/polish (read: butcher) your own head... you are just looking for trouble. its an exact science - done with flow benches and such...

also, scroll down this page & read what MM said about porting/polishing (in fact, read the entire thing), as it makes for some interesting material...

http://www.metricmechanic.com/catalog/porting-the-head.php

& this one regarding 'surface turbulence'...

http://www.metricmechanic.com/catalog/surface-turbulance.php

Quote from: Selfish;67328

hi everyone. I'm about to tackle the task of replacing the head gasket on my 91, 318i, because I really miss driving it. I was wondering if anybody has done any head polishing and porting (or any other task that I should do while I'm at it, for that matter) and if so, is it a complicated process? I've seen some guys do it on youtube and it doesn't look hard at all. In fact, I'm more concerned about messing up when putting everything together after replacing the head gasket. I was going to have someone more experienced help me out, but the guy is always too busy for me, like he was going to do it for free....so I said f** it, I'll do it myself. All input or comments welcome.

marko · « **Reply #6 on:** March 03, 2009, 01:18:06 PM »

but if you really have your heart set on it - have these guys do it for you...

http://www.extrudehone.com/auto/auto-performance.php
http://www.gethoned.com/auto.php

gearheadE30 · « **Reply #7 on:** March 03, 2009, 03:06:47 PM »

If you have the cash, Metric Mechanic has some nice head parts too

Selfish · « **Reply #8 on:** March 03, 2009, 10:01:25 PM »

hey guys, thanks a lot for all the info! I�ll keep you posted as to how did it go!

1991 E30 M42 · « **Reply #9 on:** March 03, 2009, 11:48:22 PM »

Quote from: marko;67566

unless you trully know wtf you are doing - do yurself a HUGE favor & do NOT port/polish (read: butcher) your own head... you are just looking for trouble. its an exact science - done with flow benches and such...

+1

There is a science to it, and if you are not familiar, you should not attempt, size and shape are huge factors in the final flow. You can actually loose horsepower if done incorectly.

Boyracer · « **Reply #10 on:** March 04, 2009, 05:26:10 AM »

I would not be so harsh about small DIY headwork :eek:

You can remove irregularities left by machining ports, remove step between valve seat and port/combustion chamber and of course match intake manifold and head ports in case they are not perfectly aligned. Doing those should not lose any power, altough gains might not be huge either.

If you really want to modify port shapes and dimensions, then there is good possibility to ruin the head.

Restonightmare · « **Reply #11 on:** March 10, 2009, 02:00:34 AM »

Quote from: xwill112x;67405

yes, but best setting is factory.

"The best setup is to adjust the intake cam to 5 degrees (advanced) and leave the exhaust cam alone. "

That's false then?

318/6 · « **Reply #12 on:** March 18, 2009, 10:35:29 PM »

Quote from: xwill112x;67405

yes, but best setting is factory.

For midrange, I agree.