Just wanted to know the benefits

 

I assume you're talking about porting and polishing the heads. Typically, it smooths imperfections in the runners and combustion chamber. It allows the engine to breathe better, thus get more power

 

More can be gained for less.

 

True but there's nothing like building an engine a little to raise responsiveness and overall power. Port and polish the heads & intake plenum, bore the throttle body, balance the injectors, and you've got a nice baseline to make the most of other "adders".

 

P&P requires removal of the heads. If you're going to go through all that trouble you'd better be stuffing that engine with other goodies. Otherwise.....

 

How do you go about doing all of that? Is there a write up? and are the gains worth all the work it takes?

 

1. Save your money. Get bolt-ons first.
2. No because there's no one right way to perform headwork. To get it done right it takes a lot of trial and error on a flow bench. Most mom and pop machine shops have never dealt with VQ heads on a consistant basis. You screw something up and the heads could end up flowing worse than stock, be more detonation prone, or lowering the compression ratio inadvertantly. And no, it's not a DIY job.
3. No. Now if you want to build a motor with cams and other goodies then that's another story. I'd say yea go for it. Otherwise, no.

 

3.5L cams would IMO do better than a P+P job. It's just a lot of trouble for the little performance improvement you get. There is so much more to do that will add much more throtle response / performance. Not to mention, it's not a cheap job either ...

 

Several wise men in this thread have already said something along the lines of... "More can be gained for less."

Keep in mind that the heads do not circulate air, that's the intake and manifold's job. With a FWD VQ, our intakes are fairly well designed compared to other cars.

So, as others have said, it's really involved, hard to find people with the right experience to do so and when you do they will definately charge you for it.

Now, with all of that said, you question was 'what are the benefits?' You should net about 1/2 HP per every CFM of air moved over stock.

Most P & P jobs get their real gains from the valve seat. This however is usually with the same lift and valve characteristcs as before the P&P. So just as JztMax stated, more aggressive cams would most likely net you more power.

Not a very well organized post, but.. hope that answers your questions.

 

I DISAGREE I PERSONALLY HAVE A SET OF HEADS AND YES IT IS A DIY JOB, you can polish the exaust ports and intake ports and beyond the valve seat there is alot of meat that can be taken out w/out taking overall integrity away from the head. the intake side can be enlarged and made for a better flow direction to the valves. so yes what does P&P do well for one lessen knock retard which VQ engines are prone to which also loses alot of performance, better mileage due to better efficency, and overall better airflow with or with out cams, cams w/p&P is most ideal. So when you do get your motor ripped apart its worth an extra day to spend doing some work to the heads

 

Until someone shows me a dyno or timeslip that betters Dandy's 13.00 or 220whp, I see no reason to dig that far.

 

i would not p & p unless your rebuiling the engine, going all out for performance. just doin the p & p is a waiste of time and shouldn't really be done on a maxima unless your doin what i stated in the first line.

 

No flow bench data @ various valve lifts no care. Seriously.

 

You DO realize that the intake ports are supposed to have a certain roughness to them for a couple very important reasons, right? Probably not...