hey, my engine is taking a lot longer to built than frist thought. I'm thinking adding a nice port and polish since it is there and may never be done. For a port & polish and valve job, they are asking $900 Canadian.
Will there be significant benefits from this investment, or should I just not even bother?

Thanks

 

I say do it if you plan on upgrading the cams it will make a noticable differance. How much is that in US money?

 

i wouldnt bother unless you plan on upgrading to larger turbos and going for some seriously high HP

 

thats what I have been leaning towards, thanks

 

Porting the heads, is the most sensible mod for anyone considering rebuilding the block; IMO. Porting the heads with valve jobs & cams help keep the power where it is suppose to be, in the top end. If your air/fuel in & exhaust out is restrictive, however, great your rebuilt may be, your potential will still be limited.

G

 

where in canada are you at? What shop is doing this?

 

Simple Match Porting makes a nice difference and easier on the pocket book than a full Flow Bench P@P and can be done urself.

Although I dont know just how well the Z motor is Match Ported from the Factory.

 

Like Phunk said.....the flow on these heads is very good. Unless you need to go for big boost levels, cams, etc, then it is not really warranted. If you can get a good gasket port matching that would be good enough. When I ported and polished my built motor it really only made a difference with the JWT cams and the higher boost levels combined. Be very gareful with who you get to do the port and polish if you do decide to go that route. You can do just as much damage to flow by hogging out the runners as you can from just cleaning them up a little to increase the natural flow of the head.

 

thanks you have a good point!!

 

I disagree, unless you are going for huge power, the stock heads flow fantastic. The intake manifold/plenum is the part that is in dire need of an upgrade for pretty much all motor builds. Gaining 2-3% (average for worked over VQ35 heads) flow with very pricey headwork isn't really worth it IMO. With a serious build you'd just be better of buying a set of race heads from cosworth etc.

 

Im going for around 500-550whp with out porting or polishing and i didnt sleeve my block. I do have cams though so i will get that power on lower boost.

 

You have every right to disagree; but the fact still is that basic cylinder head porting will improve the performance of any production cylinder head by removing flaws that come through mass production. Porting reduces the restriction in the engine's intake and exhaust tracts. Reduce that restriction and you let more air into the cylinders. If you have more air, you can add more fuel. The result is increased horsepower. Nothing comes close to a good set of cylinder heads.

And, I would be most curious to know where you got the figure of 2-3% gains for ported VQ35 heads over stock, and whose pot heads are you comparing to and with.

G

 

For the money, Id just have everything up there gasket matched. Unless your willing to shell out big money for an EMS and want alot of power, then dont bother with the heads. The gains per dollar is for NA cars. At most change to a more aggresive cam.

 

To realize the benefit and full potential of a quality p@p job you can't stop there. Consider a better flowing intake mani, more aggressive cams, maybe bored TB and bumping up the rev limit. Don't be overly concerned with whether or not you'll be running big boost or not. Doesn't really matter in this instance because all you're after is improved "flow".

Look at it this way: you can have a med. frame turbo squeezing 20psi and flowing 375CFM or a large frame turbo squeezing 9psi and flowing the same. If the path from the comp outlet to the cylinder is obstructed that flow rate will drop regardless of boost and turbo size. Also, a good p@p will dictate how well those cylinders fill and evacuate as well.

If you do decide to go through with this insure that the person doing the job knows that this for a FI and not N/A. There's definitely a different approach taken when p@p'ing FI heads. I think N/A is a little more demanding in that a good set of heads not only flow well but are "tuned" well.

 

I never said that it wouldn't improve anything at all. Furthermore, the last thing I need is a tutorial on what a P&P job accomplishes. I'm just saying that the risk & cost/benefit ratio just isn't there in this application.

I couldn't agree more, and the stock VQ35 heads fall into the good set of heads category for me. It's not like were starting with some crappy 2 valve head. Four valve heads are typically very close to their maximium potential from the factory.


People whom have and still do build these motors. You know who they are and you can ask them for information if you so choose.

 

He got tutorialized to the Max