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Porting heads, what does it do?

Discussion in 'The Garage' started by newbe73, Apr 15, 2002.

  1. newbe73

    newbe73 Registered Member

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    Well I took the head off to get it rebuilt. I was just wondering what head porting was and how much of a power and hp increase there would be. I have herd allot of people doing it and I was just wondering how much it would cost, what head porting is and does? Thanks if you can help me out.
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    You can port the the combustion chamber, and you can get a valve job. Valve jobs help increase flow at higher RPM's. So for a 4x4, it is not always good to get a hardcore vavle job. I have heard a good 3 angle valve job can help though. I have also heard of pocket porting, and or porting the combustion chamber. I am not sure if what all that does beside help increase flow threw the cylinder.
     
  3. weisel

    weisel 1/2 ton status

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    I think that the biggest thing is to match port the heads to the intake manifold using the gasket as a template. The castings don't match up the ports right. These lips cause turbulance in the flowing air and rob power. So, they are ground out to match eachother and flow better. I have no idea on how much they cost, always done them myself.
     
  4. newbe73

    newbe73 Registered Member

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    wow i hoped that i would get more responces cuz i still do not know what it does and everything but hell i guess if you guys just wanna read it and not help me out you can
     
  5. Hossbaby50

    Hossbaby50 3/4 ton status

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    If you got the heads at the shop, then just have them do a 3 angle valve job, and then ask them what they would recommend on your application.
     
  6. BorregoK5

    BorregoK5 1/2 ton status

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    Porting is a rather vague term which when used by itself doesn't bring about a direct answer. I'm usually pretty satisfied with my chamber volume so the majority of my porting is behind the valves which is known as pocket porting. You can open this area up to lessen valve shrouding/restriction, add surface turbulence behind an intake valve (to excite 'wet' fuel on entry) and slightly improve vacuum. I often port the runners to increase their flow or remove cast imperfections as well as port match the intake to head (a restrictive intake gasket can add turbulence to wet fuel on the runners and improve bottom end, non restrictive improves high end flow). Combustion chamber porting is usually to unshroud the valves(or spark plug), shape an intake charge or change the compression ratio. Most important of all though is getting the proper equipment (or building you own but sacrafice flow number knowledge) to match the flow of each intake/head port, runner and combustion chamber to each other so you balance the system. I think people just didn't understand which type of porting you were asking about.
     
  7. i just like the "excite the wet fuel on entry" part! LOL! seriously though. is there a noticable difference in power by simply port matching the heads to the manifold? will i notice a difference just doing that and a regular valve job? thanks
     
  8. BorregoK5

    BorregoK5 1/2 ton status

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    I'm passionate about engines but hadn't noticed the romance in my writing! LOL I could say yes that port matching would make a noticeable difference but I'd probably be wrong. There are so many factors there between hardware differences and a persons perception of change that make it tough to answer. It really depends on what your looking for. I've run screens between the intake and heads before which vaporise any fuel passing through them, its a huge restriction but it made absolutely mad bottom end... but no top end! Some people polish their intake runners to increase velocity but suffer from fuel puddling, other rough up the runners to create surface turbulence and remedy puddling smoothing out idle. Matching the intake to head generally helps by removing restriction, but if your gasket was already smaller, then it was creating more turbulence than you removed... as I've shown above, that may not be a bad thing depending on what your trying to build. But matching your fuel charge to each cylender makes a big effect on overall power. A good example is an old chevy truck my dad owns. He bought it 10 years ago with mismatched heads (1.72 intake on one head / 1.94 intake on the other head) It has always run smooth, has great compression but has a funky power band and eats gas. It can however pull a heavy load all day long up any hill, and suprisingly gets about the same gas mileage as any other time.

    Forgot the valve job, a good 3 angle is a good idea and will help, yes.
     
  9. CaptCrunch

    CaptCrunch 1/2 ton status

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    Hmmm... I sort of agree.

    Like B said... porting is kinda vauge and greatly depends what heads you have. Some heads can be worked more then others. Number one... let's deal with tha valve job.... I feel this is the first essential work needed. This I especailly recopmend on any new aftermarked heads as they all are pretty rough out of the box. Second... porting down the valve guide is the next bit that will gain you some air flow. All heads seem to have a ridge here that greatly restricts airflow. Another area that is a large restriction is what is refered to as the "radiuses". This is where the ports meet the valve seat. You can also get into further bowl work, but I highly recomend that this be left to a professional as it varies greatly on the head you have.

    Now the runners... again basically you want to smooth out any imprefections or ridges. Port matching is greatly overrated IMO. There is very VERY little to be gained on a non-race motor here and generally is more expensive then the basic bowl work. You essentiall are just trimming the ports to fit the gasket exactly. The bad thing is that if you take too much you head will be ruined and will not seal correctly. Pooling is generally caused by imperfections in the porting or polishing. The polishing helps a little with flow, but not much. It is generally done to reduce carbon build-up which also helps reduce detonation.

    Now what it does... expect anywhere from 10 to 30 hp from the full, non-major port job. It varies greatly on your combo though. Just got done porting a set of heads for a 351W w/ Rousch heads and man did we get some improvement. Generally port work does more effect to the exhaust side of things then the intake. So throw all this together and looking at it for a 4x4 application... well depends on your heads, the rpm range you want power in, your overall combo, and of course money.
     
  10. BorregoK5

    BorregoK5 1/2 ton status

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    After reading my post, I see where you might disagree (it was late/forums/images/icons/crazy.gif). While I made reference to restrictions causing 'good' turbulence, I was refferring more between a polished port surface puddling as opposed to a rough one which helps atomization, but didn't say so. A high reving engine would be better suited for a polish job than a low rev torque engine. A polished intake ports puddling issue(due to fuel sticking to the smooth edges and traveling down the intake on the sides as opposed to remaining air born) can be overcome by making a thin ridge just underneath the circumfrence of the intake valve for some applications. Some people refer to puddling as fuel left in the intake/runner in imperfections... I've heard it both ways. Teardropping the valve guide is a great way to improve flow as well, good point.

    Something I think we both left out though was to make sure you get any porting work done before your valve job. It's easy to slip and nick a perfectly good 3 angle job.
     

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