Z1 Performance

iTrader: (564)

maybe you know that....but having owned and built both, the are equally fun when properly executed

scratch137

iTrader: (7)

In the nismo spec2 heads, do they actually replace anything or is it all port/polish work? I ask because i was thinking about going to a port and polisher localy and have him do my heads to the specs of the nismo ones, but i dont know if it is just port and polish work or whatever, or if they port and polish and also replace parts. Basically, can i achieve nismo type heads through port n polishing or do i need to actually buy new heads?

Z1 Performance

iTrader: (564)

the NISMO heads are a totally different casting

smaller combustion chambers which net you alot more compression

nismology1

Basically, VQ30 head casting including 46cc combustion chambers with VQ35 intake ports, ported and polished, with titanium valvetrain. A more compact combustion chamber >>>>> increasing piston dome.

scratch137

iTrader: (7)

So i cant replicate these by just getting some headwork done? Ok, well were can i get these heads, with minimul wait time? Also, if i did get some headwork done, what would be a good route to go? I mean port polish and stuff but what else could i do to achieve equal if not better results then the nismo or similar?

nismology1

You could get the nismo heads through Z1auto and i'm sure there are other vendors. But these are on a made-to-order basis and aren't bolt-on.

https://my350z.com/forum/showthread....ighlight=heads

scratch137

iTrader: (7)

So from some port and polish work, i wouldnt be able to get the same gains as the nismo?

Z1 Performance

iTrader: (564)

no, since the NISMO heads raise compression as well

heads are available from us

Last I checked there were a couple sets available but it changes on a daily basis

http://www.z1auto.com/prodmore.asp?m...ine&prodid=923


and here are the ti valves you'll need in order to install the heads

http://www.z1auto.com/prodmore.asp?m...ine&prodid=921

scratch137

iTrader: (7)

So i cant port and polish my heads to achieve higher compression? And the nismo heads, those valves in the link, do i need to buy both the valves and the springs? And will they work w/ any cams and basically all i will need is the valves and they are good to go?

Z1 Performance

iTrader: (564)

porting and polishing, in an oversimplified nutshell, promotes faster velocity and better combustion. The only way you can increase compression with your stock heads is to fit pistons that have a higher compression ratio than stock

For the springs, you can use any springs you like, from Supertech to Ferrea to NISMO - but those valves do have to be used

In terms of cams, yes any will work, though would likely want to go for something on the aggressive side to really make use of what those heads can do (Tomei 272 or 280, NISMO Spec Units as found on our site, JUN 272's, etc

scratch137

iTrader: (7)

Ok now i understand, thanks much. Good to get a straight forward answer :-D. But 1 thing you mentioned about getting higher comp, how does nismo raise compression with their heads w/o new pistons?

Z1 Performance

iTrader: (564)

Compression is the ratio of the cylinder volume when the piston is at the bottom of its stroke cycle in relation to compared to the cylinder volume at the top of its stroke cycle.

So anything that affects the above affects compression - piston shape, combustion chamber cc, headgasket thickness, etc

scratch137

iTrader: (7)

i seeeeeee lol. Sounds good to me lol. I wish i could just make my combustion chambers smaller w/o buying new heads lol shucks

Z1 Performance

iTrader: (564)

technically you "can" - but what a can of worms you would be opening up, not to mention the cost ..... makes me queasy just thinking about it!

The "cheap" way to get compression is pistons. Several manufacturers offer off the shelf pistons that have higher compression than stock. Also, most piston manufacturers will build you a custom spec piston to achieve whatever compression you like as well

nismology1

Annnddd...
hehehe...

nismology1

According to this post, nissan now sells the heads complete with the valvetrain.
https://my350z.com/forum/showpost.ph...&postcount=129


And can you absolutely confirm that the excessive valve clearance issue with off-the-shelf camshafts has been rectified? Thanks in advance.

Sk8fe

iTrader: (5)

Although for an LS2 GTO, here are good pics that illustrate what LT headers look like. Long Tube headers will have a large collector at the end of the pipes and have the "elbow" kink to start heading back towards the rear of the car. The SLP headers shown are technically LT headers, but are designed more for ease of install rather than the Kooks, which are designed to wring out the last pony of horsepower. LT headers definately have a deeper sound and provide more HP gains, but ground clearence can be an issue and not recommended if you are going to or have lowered your car's ride height.

Sharif@Forged

iTrader: (92)

+1000

Most tuners in Japan are extremly overated, IMHO.

Reyes5937

iTrader: (6)

So whats the difference between the nismo heads and the cosworth heads?
Do the Cosworth heads raise the compression like the nismo heads do, are the chambers of the Cosworth heads same of stock heads?
Are the nismo cnc ported like the Cosworth??
Will the nismo or cosworth benefit any more form a port & polish, extrude hone or do these heads come fully ported to the max?

Z1 Performance, Sharif@forged, Sam@GTM, Jason@Riverside, or anyone please share your knowledge.

Thanks a million
David

Sharif@Forged

iTrader: (92)

Cosworth heads have 1mm oversized exhaust and intake valve, are CNC ported and polished, come with a full Ferrea valvetrain, and designed for NA or FI applications. They have some fairly good improvements in airflow over stock, but they are not a nasty FI head with poor low end power/idle characteristics. The combustion chamber is unshrouded, which results in a slightly larger chamber, and slightly lower compression....not by much, however.

I am sure Adam can chime on the Nismo heads, since I know very little about them, and have never used or sold them.