Does any one on here have ported and polish heads.I was wondering how much of a gain could I exspect from that? Ok I know some of you have ported intakes how much did you get out of that?

 

I know "Aaron92SE" will be posting here soon. He's got a Ported & Polished lower & upper Intake Manifold, & Ported Throttle Body. Here's a link for Pics. http://www.littlebabywebs.com/maxima/tbpage.htm & for the Intake Manifold http://www.littlebabywebs.com/maxima/intakeport.html

 

i say ask the question on Z31.com, they are more likely to have done that already.

Brian

 

yeah thanks for the info, but anyone knows what type of gains you will get and even what type of gains i will get turboed.I think thats how you spell that. Any how I think im going to try to port my elbow and throttle body this weekend Wonder if I will feel a diffrance?

 

I think Maxima-4DSC (formerly gowirelessnj) had his heads ported and polished, but that was on a VE.

 

P&P is better for N/A....for FI you're better off spending your money elsewhere.

 

You will notice the gains, but I'm not really sure how much gain. I ported some heads for this guy, who had a nonturbo: LINK

Here's a pic of a head I ported on top of a stock one. The top one still needed the final polishing stage when I took the pic. The smoothness is there, but the shine wasn't completed yet.

 

IMHO i dont think its worth the time (and by time I mean headache)

 

did you need to source larger valves?

Brian

 

I didn't change the valves. I've been told by many people that do a lot of head work, that since the valves are already pretty close, you would be risking a crack between them by going any larger on them. I guess if you could work out an oval valve design, it would be nice though. Anything's possible with enough money

 

i was always under the impression that that is the opposite

 

depengin how they are done you can gain quite a bit of port and polished heads. I port an polish motorcycle,quad and snowmobile engines frequently as well as a friend of mine owns a flow bench and professionally ports drag bike engines (his bike runs 8.90 in the quarter N/A).

You dont need to source larger valves unles you plan on doing some other VERY heavy work on the engine since with porting what you aim for is velocity and not volume.Overall you start with a slightly larger mouth that tapers down as you get to the valve to speed up the velocity of the air/fuel mixture to help force the exhaust (used force for lack of a better term) out of the cylinder.

At this point thoguh you cannot have the bottle neck so you have to have everything from the intake tube itself through to the head either the same size or slightly larger to get maximum effect.

I gueess to answer the actual question is if you noticed a gain from a ypipe and a cold air intake you will DEFINATLY notice a power gain from a good port and polish job.Should be an easy task to gain 20 horsepower out of it if you have eveything else tuned right.

BJ White

 

My understanding is that because the turbo is forcing the air through the manifold at higher pressures (and therefore velocities IMHO) than N/A, that there isn't a pressing need to make the air's path as restriction-free as with N/A. Will you see gains by P&P'ing a turbo car? Of course. I just feel like that for the $600 or so it'll cost you, you could use that money for something else in a turbo engine (bigger injectors, better engine management) and gain more HP per 1$ spent. My $0.02.

 

i'm going to say that i agree w/ this explaination.

 

it seems that since a turbo setup would be flowing more air through the engine that you'd want to maximize how much air the heads can flow. i would think that if you dynoed a car stock, stock with a port and polish, turboed, and turboed with a port and polish that you would see a bigger difference in power on the turbo one.

oh well... either way there are gains to be made but it may not be very cost effective yet.

 

that's the point...the gains are there...but there are so much other stuff you can do to make more gains that P&P should not really be considered at the moment.

also keep in mind japanese castings are quite good so don't expect the P&P job to gain massive hp numbers on a NA motor.

 

It will help both an N/A or F/I engine. Here's a link from a post i found on z31.com.
http://www.redz31.com/pages/headwork.html

The guy claims that it feels faster at 10 psi than it did at 15 psi without the port and polish.

I actually just finished porting and polishing my heads last week, i also bought ferrea oversized valves (1mm oversize) and hopefully will get turbocharged by january(JWT is taking forever w/ my ECU ) i have pics(port & polished heads, oversized valves, jwt s2 cams, jwt springs, gt30r turbo) if anyone is interested, i can email them to someone so they can post them. My heads are at the machine shop as we speak, they are just putting them together.

 

i think you're missing the point...yes it helps NA and FI..but if you're currently running FI...you have a lot of other things you can do to make gains other than P&P.

feel free to send the pics to DanNY@maxima.org

 

na, i understood what u meant, just seemed as if mizeree was saying that there wasn't much of a gain, 30rwhp seems like a good amount of hp(at least that's what the guy claims) VG top end sucks, so a p&p will help all throughout the rpm band. i have pics of a VG head cut into 3 pieces to show the actual restrictions. Dan, i'll send u pics tonight.

 

hey, could you send me some pictures also? i definitely want to see your setup.

i'm been thinking about getting the oversized valves as well but can't decide whether or not to yet.

 

sure, where would u like them sent to? i'll send them tonight

 

heh... i guess it would help if i put an e-mail address

mark@mtcmotorsports.com

 

No, I know the gain will be larger with a F/I setup vs an N/A setup (all mods basically respond this way, because again more air is getting crammed into the engine). But say a P&P cost $600, I feel like you could get more than 30HP spending that money on something other than a P&P. That 30HP figure is just a butt-dyno estimate anyway, and he even said himself "in the upper third of the rev range". Just MHO. To expound on my reasoning above, a turbo effectively adds energy to the air going into the engine. Therefore, it is not as imperative to ensure the air doesn't lose energy, vs an N/A where P&Ping, and extrude honing, and all those "enlarging, smoothing" mods are basically making the path for the air as effecient as possible, so the air doesn't lose energy as it travels down the intake path and into the combustion chamber. If the air path in a turbo engine is restrictive, turn up the boost 1psi -- the energy added by the turbo will overcome all the inefficiencies in the path.

 

yeah, that's understandable, but i did the porting and polishing myself. My friend taught me how to do it and i just had to buy the proper tools to do it. Cost me about $120 for carbide bits, die grinder, and emery cloth bits/polishing bits from summit racing. It only took me 2 days in between jobs to do everything.

These are just some of the pics i have on my work hard drive, i'll have pics of the p&p up tonight.

http://members.aol.com/bryanoftexas/maxima/

 

well hey I was just throwing it out for an idea. Im going to check around for a price on it. Just trying to keep brain storming on how to get it faster after tunning. Im going to port the elbow and throttle body this week end since it will not cost anything. As far as heads ill let somebody eles milk that cow.

 

There are other factors that could cause that, even if it was a proven dyno difference.

For example (sample numbers), you have a turbo that meets its maximum efficiency at 10psi. the difference in 9psi vs 10psi may be 5hp. The difference from 10-11 may be 6psi. and so on...listed below

11-12 5hp
12-13 4hp
13-14 3hp
14-15 2hp

So essentially, the performance can gain up to a point, then the turbo is heating up the air so much and losing enough efficiency that the gains reduce. As psi increases, the psi/hp ratio worsens and eventually would likely reverse to actually losing hp.

I agree with the statements about efficient spendage of money...on a turbo, the money will likely give more performance if spent on a better turbo or intercooler than if spent on porting. however, if you have the engine apart, plan to P&P one day anyway, have the money to spare, you might as well do it then.

On a nonturbo, intake velocity is important. Imagine if your car ran without vacuum. you would yave 100% volumetric efficiency. Likewise, you have a very short period of time in which the intake air has filled the cylinder and the intake valve is not yet shut. At this time, if the velocity of intake air is high enough, it will actually give a slight positive pressure in the cylinders....thus achieving over 100% volumetric efficiency is possible. Now, I am not saying it is possible on these particular heads, just that it is possible to do. If you actually wanted to do this, you'd likely be paying about $3000-5000 and sending the heads to somebody that does work for Nascar. On these particular engines, and the budget most of us have, the goal must be to just increase volumetric efficiency, not to get over 100%. If I'm not mistaken, somebody long ago said these cars run from the factory at about 80% efficiency.

For those that don't understand this: Lets say that you have your car turned off and the intake valve is open. You will have exactly atmospheric pressure in the cylinder..which is equivalent to 100% volumetric efficiency. WHen running, there is vacuum and the intake is less dense than atmospheric pressure...thus there is less mass in there.

 

I uploaded the rest of the pics i took. The heads are at the machine shop right now getting put together and surfaced. I wish i could just put the heads only and dyno a before and after to see what gains u could get from a good p&p, cams, and oversized valves, but money-wise, i really dont want to have to pay for new gaskets and change the injectors again. i'll post pics of the heads when i get them back. i'll keep u guys updated.

 

What is the porting and polishing costing you, and where did you send them?

 

yup...heads, upper & lower intake, throttle body. sent them to my buddy at the machine shop when they were off the motor and he did the custom job for me. hard to tell how much power it actually gained cause after the motor was rebuilt this car hauls azz

 

But how much is it costing you?

Reason I ask is because I've done a few sets for the z31 guys for $400 a pair and wondered if that's about what you guys have been paying.

Porting the lower intake is wasted money...I did mine, but really the work put into it isn't worth what you'll gain...cause you won't even notice it.

 

Porting and polishing only cost me $120 for all the tools and bits to do it. All the labor on that was free, b/c i did it myself. All the pics i took were before i took them to the machine shop, they were already ported and polished. I dropped off the heads at the machine shop for a multi angle valve job,cleaning,put them together, and to resurface them. I got the cams, springs, and shims from JWT. Valves are Ferrea 1mm oversive. All i'm waiting on is the nissan dealership to deliver some new retainers. I should get them back by tuesday.

 

cost me 400 bucks since i knew the machinist....that how u spell machinist ?? LOL

 

How do you know what you ground off did anything? Did you get a chance to bench flow the heads before/after? How do you know you ground off exactly the same amount on each port? Thanks

 

Well first, we cut an extra set of heads into 3 pieces so we could see how much meat we had to work with and also see where the actual restrictions are. The guy who taught me how to do it(who also works for me) has been porting ford 302 & 351 heads for over 20 years.This guy used to get people into the 11's after his porting work,cams,intake. I know the vg30 heads arent as restrictive as a 302 head which is one of the reasons we cut the head into pieces. i have a friend that runs a machine shop that could basically perfectly port them, but i wanted to do it myself. I want to be able to say that i did it. We basically opened up all the restrictions. I measured the ports with liquid to make sure they have the same internal volume and the rest was done by feel and by eye. I'll get some dyno #'s soon when everything is put together. Like i said I wish i could just put the heads on to see what difference the heads would make by themselves, but money-wise, it doesn't seem feasible.

 

Sounds good to me. Thanks for the explaination.