Porting Heads. Interesting read

[hokey]

http://mototuneusa.com/
sign up and read about high velocity porting.
EDIT: some/most of us were wrong

[Guy]

http://mototuneusa.com/
sign up and read about high velocity porting.
we were all wrong!

Speak for yourself, one of the reasons you use a sierra 1300 head on a vitara 1600 block is the smaller intake ports enhancing bottom end response, but you port the exhaust side to fit 1600 valves to get rid of the spent charge faster and more thoroughly..

Well thats why I did it anyway

[RV80]

I see they have bikini girls

[hokey]

i had never heard of this before and everyone always craps on about port and polish

[460cixy]

it was proven with the 4v clevland heads. the ports are just stupidly big. absolutly no power down low fuckin pig to drive but big revs got big numbers. so you use 2v heads and inlet valves but use the 4v exaust valves and port fuck out of it. its nothing new small ports and inlet runners= more air speed and alot better responce. and as far as polishing goes its just a wast of cash.

[hokey]

wow i am very far behind:(

["CANADA"]

screw the spaggetii ports...im waiting for more development into sleeve's...



something for you all to think about...

[hokey]

care to elaborate for those who don't know what sleeving is?

[CHILLI 2]

Remember an engine is basically an air pump,so what comes in must go out as efficiently as possible.Most motors are set with longevity in mind rather than power and with some extra tuning can gain large increases of horsepower.The old 20l Escort/Cortina was one that comes to mind as the inlet valve and port is huge but the exhaust valve and port is to small so in order to get them to go harder you fit a larger valve and enlarge the port a little this makes a huge difference there is also some misconception that raising compression is a sure fire way to ad horsepower,while this may be true in most cases i found with my Escort while i was waiting to fit a turbo to my engine i was running it with decompressed pistons and reshaped combustion chambers and i was very surprised how well it went!i put this down to the fact that i was possibly getting better flame travel therfore burning more gases and producing more horsepower.

[chunderlicious]

i have known for a while about polishing being bad for the head as you want the fuel to atomise as much as possible and by smoothing out the valves and intakes you stop the fuel from atomising and cause the fuel to stick to the sides of the intakes.

[skootin]

This solution is for motorbike engines which obviously works well.
You have to remember the difference between a high revin bike engine and a automotive engine there is major difference in the design and characteristics how the two engines work all bike engines have short intake runners (small)and most car engines have a longer intake runner which obviousy makes the port larger. The 4V clevland head is huge yes and the 2V port smaller but there are parts of the 2V port which must be opened up to give more air speed because of the direction of airflow. Motorbike heads are usually a straight port directly onto the back of the valve. The automotive 4cyl heads are being designed more and more like motorbike heads. One thing that is different also is a motorbike does not have alot of torque because of the weight of the bike it is not a major concern where as a car or truck weighs more and requires torque which is all developed from low rpm until horsepower takes over in the high rpm,
So yes different ports require different techniques to achieve the maximum power. But we allready new that.

[F'n_Rover]

i have known for a while about polishing being bad for the head as you want the fuel to atomise as much as possible and by smoothing out the valves and intakes you stop the fuel from atomising and cause the fuel to stick to the sides of the intakes.

IMO - old wives tale. polishing is a very worth while mod, especially the exhaust. The gains on the intake are probably not worth the effort though.

You would polish the exhaust ports for the same reason that you polish the chambers - ie : to reduce heat transfer into the motor.

extreme porting is bad - cleanup and balance porting is the best thing. Just dont go stupid.

[chunderlicious]

or get it professionally flowed to the extractors and intake mods (carby, blower, etc.) and i meant only the intake manifold, the exhaust should be nice and smooth, just like a nicely tanned, good lookin, hot bodied blonde nympho....... ill be right back

[leeo]

the reason porting is done to an engine is to reduce tubulence/drag just like airplane wings. they are smooooth not rough like cast engine parts.Performance gains are small for the cost.Get more power doing stuff like expensive uni filters and extractors and good 2 1/2 or 3 inch exhaust systems.Still want more power then you look at porting and forced induction and bigger injectors etc.

[Beastmavster]

Porting has differeing effectiveness on differeent engines, based on how inherantly bad the port design is and what you want to achieve.


Most modern engines gain little benefit from port work unless you're radically changing the intake layout. A couple of kw maybe, but it's a lot of work and expense to gain it.

Dont be suprised if your ports have quite unusual shapes, asymmetrical is the norm now for decent port design.

[bilby]

just buy brodix alloy heads and u'll be smiling
























but ya wallet wont be

[bru21]

i have known for a while about polishing being bad for the head as you want the fuel to atomise as much as possible and by smoothing out the valves and intakes you stop the fuel from atomising and cause the fuel to stick to the sides of the intakes.

close but its the opposite. as fuel which has not yet atomised falls to the bottom on a unpolished (still ported yet left roughish) the increase in eddy currents due to the increased turbulance cause a rapid swirling of the vapour and an increase in atomisation, this is aided by the still unatomised fuel being trapped in the small grooves and being bioled off by the transfered motor heat and direct throughflowing evaporation.

polished inlets cause the fuel which is not atomised to sit at the bottom then with reduced eddy currents, reduced heat transfer etc stay there till higher velocity wher it runs down to the motor causing a rich situation. this can play havoc with any motor especially fuel injected ones that are not capable of allowing for these erratic changes at the o2 sensors etc. in reality though increased fuel consumption is the main result as in efi the fuel atomisation is pretty good.

[sudso]

it was proven with the 4v clevland heads. the ports are just stupidly big. absolutly no power down low ***** pig to drive but big revs got big numbers. so you use 2v heads and inlet valves but use the 4v exaust valves and port ***** out of it. its nothing new small ports and inlet runners= more air speed and alot better responce. and as far as polishing goes its just a wast of cash.

It's all a bit of a compromise, if the inlets are too small you lose out on top end power if thats where you want it but its all still relevant to cam lift, cam timing, exhaust back pressure, manifold design, fuel supply etc etc.
A piston can only suck in the cylinders capacity unless it's pressure fed

[-Scott-]

I heard recently that hydraulic valve actuation (in development) will allow variable lift as well as timing - so you don't even need a throttle butterfly. Install the biggest valves that will fit, but use small lift/duration at low speed.

Cams are typically designed to work with a given back-pressure. Reducing the back-pressure typically has the same effect as increasing overlap. No cam = no problem Change your back pressure, re-program your valve timing.

One day...

Scott

[its fishi]

I heard recently that hydraulic valve actuation (in development) will allow variable lift as well as timing - so you don't even need a throttle butterfly. ...

BMW already use this system on the Valvetronic engines, no butterfly.