whats a 'gas flowed' head

[darren318is]

im pretty good at all things auto but one thing i dont know and really wanna is wat dis is and its advantages are

[Dan318-is]

i would also like to know this

and whats the difference between this and a port/polish?

[kidsinister]

Gas flowing involves either opening out the ports on a head, smoothing any sharp corners, basically making sure the gases flow smoothly and possibly in greater volume through the head.

Polishing is just a matter of smoothing out rough surfaces in the ports; less effective, but sounds good.

[Dan318-is]

so gas flowing is better?

what sort of gains?

iv have to modify a head in college i dunno whether to skim it of gas flow it?

[Andy335Touring]

some good info on here

http://www.pumaracing.co.uk/mainmenu.htm

[Dan318-is]

link dead my friend

[Andy335Touring]

Works for me ?

[Dan318-is]

i deleted the main menu bit an it worked

some good info on first glance mate thanks!

n e idea what gains from a gas flowed m20 head?

[tomstickland]

Most heads are cast and then machined. The machined bits usually break into the cast parts with a sudden profile change. It's near impossible to cast really sharp edges where inlet ports break into two for 4 valve engines etc.

Gas flowing implies smoothing the inlet ports to provide a more smooth inlet flow.

Porting is usually about enlarging or reshaping ports. It's an area where a lot of bad work is done. Just enlarging the ports often results in a loss of power/torque.

Polishing is about polishing surface and offers no flow benefits, and can make lose performance since a certain amount of roughness helps keep the fuel in suspension.

All three terms are mixed up with one another. For every decent set of headwork there's probably 50 sets of bad headwork.

[Dan318-is]

so which is the better of the three??

[Jon_Bmw]

For every decent set of headwork there's probably 50 sets of bad headwork.

So true, you really have got to do your research on the person you would get to do the work. Its not something you can look at and think "thats a bit rough" and half an hour later you've smoothed it all over.

You will make a mess of it.

As far as i understand:

Skim:Taking a layer off where the head meets the block, often done on rovers due to their head gasket problems. Best only to be done once, as its not so effective after that. This will increase the compression ratio.

P & P: As Tom stickland said, opening up ports, smoothing off the rough stuff, but all to easy to lose HP not gain it.

Gas Flowing: Again as Tom stickland said smoothing the inlet tracks, but i presume actually checking it with flow rates to make sure you're getting everything you can out of the head. Professional will know all the weakspots of cast oem heads so they won't be trying and then trying something else when the first way failed. It takes serious time for serious head work, not a couple of hours in 'supreme headworks for council cars uk'

Also 318-is, you say you are not sure whether to skim or to gas flow, are you sure you mean skim?

If you want a project, where you'll make noticable gains with head work, use an Mi16 head. But you probably already knew that??

[TW166Y]

and heres me thinking that it was when you grab someones head and fart on there face... sounds like a gas flowed head to me

[TW166Y]

sorry iys late and iam vrey drunk

[Hyperion]

and heres me thinking that it was when you grab someones head and fart on there face... sounds like a gas flowed head to me

[Dan318-is]

and heres me thinking that it was when you grab someones head and fart on there face... sounds like a gas flowed head to me

lol!!

iv been told by a few people not to skim an m20 head as they are already week or something?

iv got about 12 hours in the workshop overall to try and gas flow a head, but the beauty is iv got a spare one if i cock it up

what do you mean mi16 ?

i thought that was a gun lol!

[BrAdZ]

and heres me thinking that it was when you grab someones head and fart on there face... sounds like a gas flowed head to me

Hahaha soo funny

[Jon_Bmw]

and heres me thinking that it was when you grab someones head and fart on there face... sounds like a gas flowed head to me

lol!!

iv been told by a few people not to skim an m20 head as they are already week or something?

iv got about 12 hours in the workshop overall to try and gas flow a head, but the beauty is iv got a spare one if i cock it up

what do you mean mi16 ?

i thought that was a gun lol!

Well skimming is a waste of time really unless you desperatly want to increase the Compression Ratio or have a slightly warped head and i do mean slightly.

An Mi16 is a cylinder head off a pug 405 mi16, either came with an ali 1.9L block or a cast iron 2.0L block. Basically peugeot made this head very easy to modify, if you are doing this for a test and you've got to get results then you'll do much better with an mi16 head than an m20 head.

Have you looked at the m20 head to see where you 'might' get any gains by gas flowing it? Research it to see where you might gain, but most people keep it close to their hat as it were.

[tomstickland]

Heads can need skimming if they are at all warped. It does increase the compression ratio which can be a good thing. But people get obsessive about skimming heads, as if running 11:1 is going to release all this hidden power. In most cases it doesn't do any favours at all since pump fuels are having ever lower knock resistance so the extra CR cannot be used for anything useful. It generally just encourages gasket erosion or silly amounts of ignition retard which is no use to anyone.

It's the same as overboring. People keep sayinh "2.0 bored out to 2.1" as if that's going to explain a 100% increase in power.