DAREN

iTrader: (3)

as i understand it a port job just enlarges the intake/exhaust valves. while the polish just maximises the increased airflow. what kind of effect would this have on a NA car? i know that this is common of cars with overbores and/or forced induction, but would it be an effective power adder in a NA application (ve30de). if it does add power, is it throughout the powerband or is it just in a few hundred (short) rpm? i've heard that bad port jobs can cause a loss in low end and screw up the drivability of your engine. nissan made a pretty good/efficient engine to start with so i wouldnt want to screw it up.

as shown to us by maximamike (i am not flaming you) there is a "nissan kit" avialable that includes rods/pistons/rings/ and a machined crank. how does machining the crank help to make power?

yes, i know some of you have beaten me to thwe punch: in making an all motor Maxima.

tia

Matt93SE

iTrader: (44)

There's an excellent article on head mods in this month's SCC.

that thing will answer all your questions on a general level.
I don't really thing anyone has done much with the VE heads yet, so it's still kinda up for grabs as to whether it will help or not.

the VG ports look very small and could stand a lot of tuning.. but that's also partly where our low-end torque comes from.. I'll work on some stuff later, nothing planned for the near future.

Greyboy

porting and polishing helps the air flow faster through the intake and the exhaust manifolds. If you have a K&N or something of the sort, you'll get even more O2 through the engine more quickly and smoothly = more power! I think I'd do it if I weren't a broke a _ _ intern! How much does that cost anyway?

FroMan

there were probably only be minimal gains untill you are running high boost or high compression. most NA cars will only see 1-2 hp by doing a port and polish. not worth your time or $$

geoffc

porting on na engines will gain most power by shaping the ports to direct the air flow most efficiently. on na engines, if you port too much, you'll lose power. with a power adder, you want a big port.
also, you'll want to port match the manifolds to maximize power. a cam is also neccessary to take advantage of the increase efficiency.
if all port work is done correctly and the cams match well, you'll get at least 20hp to the wheels.

Nismo87SE

I beg to differ (hehe). I will agree you can't go much larger on the intake or exhaust ports, but its mainly about air flow. I believe most of the gains come from the exhaust side too. But when my heads were ported and the ISKY 262 cam was added I could easily hit 6550 in 3rd gear. My car used to toppout around 6100 in 3rd gear also I can tell I had alot more torque everywhere too. Since the labor charge is around $700-1200 for heads/cams install, if your a DIY it will take you about 3-5 days to complete. Just make sure you have either a week of vacation or another car to use. Since my car went from 5 cylinders to all 6 with higher flow heads and hotter cams it felt faster than when I put on all my bolt ons. Too bad one of my radiator fan stopped working then I had a coolant leak from my lower radiator hose and on top of that my parking light circuit when out. There I was driving home with no dash lights at nite running to the redline in 2nd gear when all of a sudden the head gasket blows . If I had taken it alittle slower maybe it would be running now. Ain't life a *****?

Maximamike

By machining a crank, the stuff on the crank spins faster with it. Therefore giving you more RPM speed and more hp. This includes things such as lightening, knife edging, balancing, etc..

Jeff92se

iTrader: (82)

1) How crappy the heads are before you work them. If they are already good, then not much can be gained. If the design is a piece of crap before, then of course more hp can be gained. But for your reference, Nissan design is fairly good.

2) How good the machist is. If he is an idiot, then you will probably LOSE power. It's much easier to LOSE power than it is to gain power.

For mild porting, stock cams are probably okay, wild P/P will probably require diff cams to take advantage of the work.