As you all know I have started on my turbo project. I have ran into a lil challenge well sort of. Im debating if I should go all out on head work port, polish, new valves ext… but as you know that type of work is costly. My second option is to replace all the valves, stems, springs ext.. for a lot cheaper.
OK so my question is to you guys, my head has about 115k miles on it. With the power goals im lookin to gain, do you think it would be effect if I just replace all the parts for less or should I go all out and get the stage 1 complete head work? I know with replace parts should be fine to maintain the lifetime on the heads wit the increased power but will it show in the performance aspect of things.
I would like to get peoples input on this… so if you had any head/engine work please give me some advice. Thanks.

 

send them off to headgames and get them done. no doubt!

 

Depends on your budget.....





http://my350z.com/forum/forced-induc...rip-event.html

I guess I will see you at this event....You are 10 minutes from this airport

 

That’s the thing I’m looking to justify the cost to power ratio..
If I can get the same gains for my power goals spending less or just going full out and doing all the required head work to get an increase in the power curve that’s the point im tryin to make. But I need to make a decision very soon cause the engine is coming out as I write this..

 

What are your power goals?

 

550 rwhp

specs

built 3.5L 8:8.1 CP
20G greddy kit
re worked heads
600cc inject

 

Given that the stock heads can hold 550whp I say it's up to your budget on whether you clean up or build up the heads. Either way with 100k+ miles you need to at least clean them up, replace seals, ect.

 

my damn car has been on 4 jack stands for over a week now waiting on these damn wheel studs. i shoulda never pounded them out til i had new ones in my hand.

 

I have ffull headwork (+1mm valves, port and polish, springs etc) and if I had to do it again I wouldnt

I know Thom00000000000001 did over 700 hp with stock heads including stock cams

 

No need to do headwork for 550 RWHP. The money is more wisely spent elsewhere on your build.

That said, if everything else is properly done and you have money left over that you want to pour into your build, having proper headwork done won't hurt. For example, I match ported my intake ports to my intake runners and exhaust ports to exhaust manifolds. I also used Ferra valves, JWT C2 cams and JWT valve springs. Roger at Japtrix said that this combination made power easier than any other VQ35 setup he had tuned. Nonetheless, my HP goal was higher than yours.


Here are some specific thoughts on your build:

1. If you want to rev to high rpms, lighter valves will help. I have seen at least one guy claiming over 8k rpm on stock valves, but I wouldn't push stock valves so hard. I went with Ferrea valves. Personally, I have never heard anything but positive comments about Ferrea valves. On the other hand, I have heard of BC valves breaking when pushed hard.

2. IF you decide to do any headwork, stick to match porting the intake ports to the intake runners and the exhaust ports to the exhaust manifolds. The time to consider opening up the intake ports is when you are going to struggle to get to your HP goal without doing so. I don’t believe this will be the case in your build assuming you have a proper exhaust system, plenum spacer, EMS, etc. Indeed, for your HP goal, increasing the size of your intake ports and/or valves will actually hurt your low-mid rpm performance.

Specifically, as you increase the size of the intake ports, the velocity of the intake air/fuel mixture at any particular rpm decreases, and tunes the intake ports/runners for optimization at higher rpm. This will reduce your low-mid rpm torque/hp. Moreover, since the stock heads and Greddy 20G TT kit will already get you well beyond your target HP goal, you will not see any worthwhile benefit from the higher rpm optimization. You may be able to run slightly less boost to get to your target HP at high rpm, but since 550 RWHP is pretty easy for the Greddy 20G TT kit, this won’t provide any tangible benefit that comes anywhere close to offsetting the low-mid rpm performance you will be losing.

Now, for someone with a goal of 800 RWHP, the story is different. That level of HP will be pushing, if not already exceeding, the envelope of the stock heads in combination with the Greddy 20G TT kit. In that case, opening up the ports would be helpful to increase max HP at the high rpms. Nonetheless, there still will be a torque/hp loss in low-mid rpms.

 

Great info, i may just decide to do the BC kit and replave all the stock parts.. that way for a piece of mind.

 

You might want to consider using Ferrea valves in lieu of BC valves for the reason noted above.

Also, if you are not going to exceed about 7500 rpm, the JWT cams/springs will provide more lift, and thus better flow. If you want to push it much above 7700 rpm, then go with the GTM cams or BC cams.

 

So you are saying Ferrea valves (intake and exhaust) are better than BC? I was considering all BC components for the headwork minus the OEM keepers..

 

this is the valves you are ref about..

NISSAN 350 Z 3.5 L - V-6 - DOHC 24 VALVE (VQ35) - 2003
F1565P E 32.35mm 5.96mm 94mm 3.5mm 22º Flo. Radial Grov. + 1mm o/size.Super Alloy Turbo appl.

 

Personally, I would not use BC valves for the reason noted above in post #10, item (1.).

Nonetheless, go with your tuner's recomendation. Show him post #10 and tell him that you have a concern about this. If he thinks I'm full of **** and still wants to use them, be sure that if they do break you have it in writing that it is his problem and not yours. It is probably unlikely that they will break and may only happen on a very rare occasion, but in my opinion the Ferrea valves are even less likely to break.

If your tuner is willing to stand behind the BC valves and warranty your motor if they ever should break, not too much of a problem other than the downtime for the motor re-build.


Not these. These are oversized, which is not what you want for a 550 RWHP build (see above post #10 item (2.)). I used the F1564P valves, which are stock size.