right a little disscusion on port polished heads.

the question is, do they really work???

now im not talking about cams, or big valves here, i mean just opening the ports up.

i have spoken to a few people, one of which used to be a touring car machanic, and i have been told, that opening the ports on a turbo head is a waiste of time, as your forcing air in and out with your turbo.

and when i had my head overhauled, the guy doing it was going to have a look to see if there was anything restricting the flow, which theres not on a CVH head.

So is spending all this money on getting your ports machined and polished a waiste of time???

disscuss

 

A lot of this depends on the head you are starting off with and what gains you are expecting to get.

If you use this alone as a method of tuning then you will see very little gains. But if you are using this along with other modifications then it will help. Being able to flow more air through the head is always a bonus, as long as its done properly.

I would never take a head off just for porting and polishing, but if I was changing cams and valves, then you may as well have it done at this point because the cost isn't a big issue then.

May as well optimise everything if you can.

But if yoy took the head off purely for porting and polishing, the costs would outwieght the benefits IMO.

 

Exspanding just the ports will add some power but you need bigger valves nd cam to really make the most of it.
If im right in saying so, the polishing helps the air to flow faster as there is nothing to restrict it, if the head is rough inside the ports the air gets trapped in the rough parts causing a vortex and slowing the air down going in and out the cylinder head, sorry if im wrong but i think thats about right

 

the way i understood it is this , when u port and polish a head on a turbo car u get a psi drop and the reason for this is becasue the turbo doesnt have to work as hard to force the air through the head there for its means that the airflow is a lot greater ....hes arally engine builder and uses flow bench as well so i belive him lol ....and as for the cvh u can port it out a lot cos of the crap inlet design

 

porting and gas flowing are only required with na motors where you want every single bhp
with forced induction , it is ot as important. it would help though on such a motor to match port at least
as for polishing , you end up with droplets of fuel sticking to the ports because it is too smooth ,resulting in a lumpy idle among other things

 

its popular belief that turbo cars dont need big ports & ported heads but its far from the truth the percentage of power that a na engine makes in power with a ported head so will a turbo engine even more so as it as a higher percentage to start with a standard rs turbo with with a good ported head will make 210 bhp with 11 psi boost as stated before on here its one of the best mods you can do to any cvh

 

LEE-RS

Is spot on, and the rest of you are frankly talking garbage It gives massive benifits in truth. My 1600 indeed made 210hp @ 11psi. The very same day, a number of RS turbo's ran, which i had a large hand in building. Std car with 16psi of boost made 177. Another std engine, running on 18psi with a pro alloy cooler, 3 in bore zorst, filter etc just nudged 200hp. And mine did 210 on 11psi on a std cam. The power all comes from the head, it just revs so much more.

The notion that a turbo just forces the air in is total rubbish. A normally aspirated engine also has something forcing air into it's cylinders - atmospheric pressure. A n/a car runs 14.7 psi of absoloute pressure if you like. We open up the ports etc and the power goes up. If we then add more pressure (using a turbo) it will flow even more air and power will go up. Blow through a small staw, then blow through several - which is easier? This is exactly how ur turbo sees it. You're blowing with the same pressure each time - but with lots of straws - there is more volume of air moving.

A worked CVH is very very good - it will flow shit loads of air.

 

so are we talking stage 3 head to get 210 at 11 psi??

I want one!

where can I get one?

 

mine works and i havnt got big valves

 

Blow through a small staw, then blow through several - which is easier? This is exactly how ur turbo sees it. You're blowing with the same pressure each time - but with lots of straws - there is more volume of air moving.



well put rick

 

NMS or CNCheads. They seem to be the better heads.

MSD can sort one out if you supply a head although you would have to ask them if they can do it(they sub contract it out to one of their mates. He does a good job but it depends if he is busy and if they will supply without doing a conversion).

My own car is on a big valve NMS head. KE jetronic cannot flow enough fuel for anymore than 11psi on my engine. I am running 14psi held and have to change gear at 5k rpm as it runs lean above that (on a standard turbo!!). I doubt that my car is above 200bhp though as it's only running standard ignition advance.

 

Hrsturbo

As Daz says.

It's the porting, throats, seat area that makes the diff more than the valves.

You need a good blueprinted engine to get that sort of power though - but it shows what's possible. Karl Norris once did a 200hp at 8psi run, although this engine was cammed - still bloody impressive.

 

hope they work i just brought one off LEE-RS

 

turboben

Get it to an engine shop, so they can check the trueness, and condition of the seats and guides.

 

what do you mean
do you know something about the head i dont

 

no lol. But i would never put a s/hand head on without giving it a once over.