Porting and polishing the head - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

twofortysx · 01-31-2002, 04:55 PM

What do they do when they port and polish the head of the engine.  Also, what kind of gains would/might come from this on a stock KA?

- Matt

Tuck&Poke · 01-31-2002, 04:58 PM

they make the tunnels that air travels though smoother and larger.  you could also increase the size of the valves for better flow.  it basicaly increases horespower and torque.  smoother and less restictive airflow on any engine means more power

White240sx · 01-31-2002, 05:10 PM

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from twofortysx on 4:55 pm on Jan. 31, 2002
Also, what kind of gains would/might come from this on a stock KA?</td></tr></table><span id='postcolor'>

The one bolt-on N/A car I know with a worked head (DPR unit) only gained a few horsepower (5hp max?). The timing had to be retarded 15 degrees to combat the detonation.

Tuck&Poke · 01-31-2002, 05:20 PM

you cant base hp gains on someone elses car.  the timing ignition retard is probably true i dont know.  but just cause one car got 5hp doesnt mean this one wont get more...or less.  it depends how much you port and how finely you polish.

whateverjames · 01-31-2002, 05:22 PM

was the head shaved? i've heard nissans pretty much come with a 3 angle job, and the next step is a 5 angle. anyone know about this.

White240sx · 01-31-2002, 06:43 PM

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from whateverjames on 5:22 pm on Jan. 31, 2002
was the head shaved?</td></tr></table><span id='postcolor'>

I don't think so; DPR didn't know he had adjustable cam sprockets so they didn't deck it. It does however have cloverleaf combustion cambers, so the compression was raised (mathematically on paper).

BTW it was a DPR Stage VI I believe.

And yes, the KA has 3-angle valve job, I don't know if anyone is running a 5 angle or not.

01-31-2002, 04:55 PM	#1
twofortysx Zilvia Junkie Join Date: Jan 2002 Posts: 491 Trader Rating: (0) Feedback Score: 0 reviews	What do they do when they port and polish the head of the engine.  Also, what kind of gains would/might come from this on a stock KA? - Matt

01-31-2002, 04:58 PM	#2
Tuck&Poke Zilvia FREAK! Join Date: Aug 2001 Location: MIA Age: 38 Posts: 1,046 Trader Rating: (0) Feedback Score: 0 reviews	they make the tunnels that air travels though smoother and larger.  you could also increase the size of the valves for better flow.  it basicaly increases horespower and torque.  smoother and less restictive airflow on any engine means more power

01-31-2002, 05:10 PM	#3
White240sx Zilvia Member Join Date: Nov 2001 Posts: 219 Trader Rating: (0) Feedback Score: 0 reviews	</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from twofortysx on 4:55 pm on Jan. 31, 2002 Also, what kind of gains would/might come from this on a stock KA?</td></tr></table><span id='postcolor'> The one bolt-on N/A car I know with a worked head (DPR unit) only gained a few horsepower (5hp max?). The timing had to be retarded 15 degrees to combat the detonation.

01-31-2002, 05:20 PM	#4
Tuck&Poke Zilvia FREAK! Join Date: Aug 2001 Location: MIA Age: 38 Posts: 1,046 Trader Rating: (0) Feedback Score: 0 reviews	you cant base hp gains on someone elses car.  the timing ignition retard is probably true i dont know.  but just cause one car got 5hp doesnt mean this one wont get more...or less.  it depends how much you port and how finely you polish.

01-31-2002, 05:22 PM	#5
whateverjames Nissanaholic! Join Date: Jul 2001 Location: St. Louis Age: 45 Posts: 2,263 Trader Rating: (0) Feedback Score: 0 reviews	was the head shaved? i've heard nissans pretty much come with a 3 angle job, and the next step is a 5 angle. anyone know about this.

01-31-2002, 06:43 PM	#6
White240sx Zilvia Member Join Date: Nov 2001 Posts: 219 Trader Rating: (0) Feedback Score: 0 reviews	</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from whateverjames on 5:22 pm on Jan. 31, 2002 was the head shaved?</td></tr></table><span id='postcolor'> I don't think so; DPR didn't know he had adjustable cam sprockets so they didn't deck it. It does however have cloverleaf combustion cambers, so the compression was raised (mathematically on paper). BTW it was a DPR Stage VI I believe. And yes, the KA has 3-angle valve job, I don't know if anyone is running a 5 angle or not.