Port And Polish

[mr_crust]

hey guys im getting some engine work done, now im getting me head re-conditioned....whats port and polishing ?? is it worthwhile doing ??any benfits from it .

thanks

[R31Nismoid]

depends on your setup

[mr_crust]

my setup is currently :

1996 R33 Series 2.

rb25det with pod, 3" exhaust and in the commin' months a bigger cooler

[cookie300zx]

if you have the heads off, you may as well get it done at the same time. save the labour cost down the track. won't really do much till you run more boost, would also be good with a larger turbo.

[R31Nismoid]

if you plan on using just the stocker turbo, or a very mild upgrade later on - no really worth the $$

[Bl4cK32]

Id say its a good thing to do while the heads off.

Remember boost is a measurement of restriction of airflow. Anything that helps the motor breathe better is good imho.

You will get better power out of it for the same boost that you had before....

On a side note, the guys who did mine and Cubes did it for roughly $200 ish...anymore spent wasnt worth the $ to power gain....

[Evan_R33]

most modern heads are designed well enough, untill you are at the stage of weening every Kw out of your car.... it's not worth it. spend that money on the cooler. you will see a result.

[RB240Dav]

As you guys were saying, porting isn't really necessary or needed at mild modding.

But, wouldn't polishing the combustion chamber be a nice measure to help control Knock if and when he plans on upping the boost?

I bet that would be rather inexpensive to just polish without porting.

[clayoth]

Any time I have had an engine apart I have matched up the manifolds and cleaned up the casting dags. I feel that this much work (not very much) is worth the effort.

[itbmils]

I agree with RB240av and clayoth

better flow = more power, more efficiently (free kilowatts so to speak)

the amount of power an engine can develop is dependent on the mass of air it can breathe per unit of time – a simple mathematical fact of life for an engine builder.

I have seen (or read about) up to 30% gains when porting the RB25 head, and I'd think it would be worth while no matter what the boost level (IMHO)

Modern heads may be good - but they are still mass manufactured and include castings and dags.

At a minimum you should look at port matching, a polish up of the combustion chambers (for a cleaner burn) and a polish up of the inlet and exhaust valve bowls. Keep in mind you may also need to replace valve seats and seam seals at the same time (if you are not doing so already)

get it tidied up - you know you should

[NickR33]

get a quote... if its more than a couple of hundred $ don't bother imo...

[itbmils]

I've just had this done on my R32 GTR - so I expect it will be more than a couple of hundred $$

steam seals will be that much

[NickR33]

yeah I don't see the point at mr crusts level of modification... unless bigger turbo and fuel system are waiting in the wings... even then I would be looking at cams instead... however it all changes if the head is stuffed and needs a recondition or you plan on running sky high revlimits

in a GTR its a different story

[R31Nismoid]

Its not really free kilowatts at all. Same could be said by adding 1-2psi in, doesnt "cost" you anything.

With a better flowing head, itll make same power @ less boost, potentially...

But if you want to make more power you need to screw more in anyway.

On a stock turbo your limited to the boost you can run, so there is no benefit either way that can be justified. Even a mild 2530 upgrade or something to 220-240rwkw

I mean i ran a 100% stock head, flowed fine for the 270rwkw on 17psi outta the gt30, 330rwkw on some 104/24psi

I was on a budget then, and i couldnt justify the cost at all.

I didnt do cams for that reason either.

It was $1000+ that could be better much spent on a PowerFC/AFM/Fuel system IMO, and it was

[NickR33]

It was $1000+ that could be better much spent on a PowerFC/AFM/Fuel system  IMO, and it was

<{POST_SNAPBACK}>

totally... I spent a grand on cams and there is no contest between the effect of that mod vs when the cooler went in... the cooler won hands down! but I kinda knew that would be the case;)

so yeah, save your money

[Al]

My head has been ported and has a set of Tomei cams. Was advised NOT to polish the head, something to do with the fuel spray, this came from the porter.

Unlike those that have not experienced the benefits of porting and cams, but still like to talk it down, i can not speak highly enough of the benefits i have felt and gained.

BUT: As stated b4, this should be done after a turbo upgrade. Wether you decide on just a "hi-flow rb25/vg30 turbo" or go crazy with a "T78", gains can be had with porting and cams.

My "hi-flow rb25/vg30 turbo", with porting and cams is making 270rwkw@15psi, compared to Ash's GT30 making 270rwkw@17psi. I have also the added bonus of looking standard, as the turbo has the factory comp cover/housing and factory shields.

Once again: these should be one of your last power mods, but i beleive that they shouldn't be overlooked.

[itbmils]

if the head is off - you should do it now - if you have the $$

you will not need to revisit the head if (when) you go for additional power upgrades

[R31Nismoid]

Unlike those that have not experienced the benefits of porting and cams, but still like to talk it down, i can not speak highly enough of the benefits i have felt and gained.

My "hi-flow rb25/vg30 turbo", with porting and cams is making 270rwkw@15psi, compared to Ash's GT30 making 270rwkw@17psi. I have also the added bonus of looking standard, as the turbo has the factory comp cover/housing and factory shields.

But you did all the mods at once, but hard to judge how good one thing is when you do a complete package of mods.

We made the same power (although would loved to have tested that same dyno to compare much more accurately) but i saved what... $1500?

More beer money for meeeeeeeeeeeeeeeeee :lol:

[Al]

But you did all the mods at once, but hard to judge how good one thing is when you do a complete package of mods.

We made the same power (although would loved to have tested that same dyno to compare much more accurately) but i saved what... $1500? 

More beer money for meeeeeeeeeeeeeeeeee :lol:

<{POST_SNAPBACK}>

I too would have liked to see a same dyno, same day, comparison, As i believe that dyno charts aren't really worth much. Mind you my car is only fully tunned to run 255rwkw, as i never intended to run over this power, with a std bottom end.

Note: Little off track

Did you save that $1500?

What about the new ic piping, oil and water lines, most people require a new exhaust manifold (You were lucky and has the GTS-R manifold), maybe an ext. wastegate, etc. When you add all these up, just to acheive a similar figure, how much are you really saving, you'll probably find you are actually spending more

Lets not forget all the hidden costs:

- More boost=less reliablity

- EPA: You mods stuck out and were obvious, the officer will really have to know his stuff to pick up on my mods. B)

[itbmils]

now now - lets settle it down girls

let's agree that port and polishing is a good thing - but only when it's justified, and I mean in terms of cost and desired performance

Let's also agree that to REALLY see the benefits - you need the other supporting mods, EG exhaust, dumps, AFMs CAMS and the list goes on

My opinion is that once these other mods ARE done - that you will see better results if the proper prep work has also been done

I also ggree - $1500 is a lot of beer (or scotch in my case )