Had some cylinder heads tested on a flow bench at a local machine shop.

My old VQ30 head, a 2001 Pathfinder VQ35 head, and a cylinder head off of a 2003 Maxima.

They used a Superflow SF-110 Flowbench at 28 inches of H20. All of the heads would only allow 0.450 inches lift (11.43 mm) anymore than that and coil bind occured.





All three Factory heads flow pretty well, as expected the VQ35 Maxima flowed the best. IMO weak factory cams and limits on lift hold all of these heads back.

Discuss.

 

Nice stuff. My dads ported and polished stock 455 firebird head flowed 280 CFM when he went 10.3s so Ill be able to brag that my stock VQ35 heads flow just as much LOL

Good to know that the lift limits the heads, I feel better about the nismo 262 cams I bought now. 0.426 lift. Can anyone tell me what the lift translates into in metric form (MMs). Because I keep hearing 10.9 mm lift for the JWT cams and 10.5 mm for my nismo cams but by my math 0.426 lift translates into something like 10.7 mm lift. 10.5 does not seem right, it gave me 10.73 mm and besides the JWT cams are said to be 0.428 lift in inches, so it makes no sense to me.

Logically JWT=10.9 mm, Nismo=10.7 mm lift, stock=9.5 mm lift and the crappy stock 3.0L cams I have now are 8.55 mm lift.

Anywho quite impressive straight from the factory, even the stock VQ30 heads seem to do pretty good for what they are (produced from as early as late 1993 in europe!).

 

Nice work. I'd like to see how the VE heads compare to these.

 

Also, extreme valve lifts will result in higher CFM on a flow bench, but not necessarily in practice. I'm pretty sure there's a point of diminishing returns for all practical purposes.

 

25.4 mm = 1 inch

so JWT 10.9 mm = 0.429" lift

I was surprised to hear about the coil bind issue past 11.4 mm, but now that I think about it the NISMO VQ35 heads make sense. Normal VQ35 cams don't work and they offer special cam blanks so race teams can cut cams with +13 mm of lift for those heads.

Im slowly putting together some ideas for an N/A engine build. Cams and induction are what hold this engine back, IMO there is no need for any porting or major head work unless you are running forced induction. Eventially Im going to have the shop clean up the heads, clean up the bowl area, and check for even flow on each cylinder.

 

Well the coil bind issue can be fixed with aftermarket valve springs, to a point. The JWT springs, for instance, don't bind until .500". The primary issue with cams with extreme lift is the cam lobes running into the edge of the buckets. That's where the nismo heads come in. They require cams (nismo Type A and B) with a smaller base circle so extreme lifts can be used. Trying to use regular production VQ35 cams will result in excessive valve clearance. The bucket diameter might also be wider on the nismo heads but i'm not sure.

 

Ok good to know, eventially I will re-bench with the Supertech valvetrain and see how much more lift I can get. I don't expect the flow #s to be better just to see if I can get to 0.500" or more. Both the Pathfinder and VQ30 Maxima intakes and all exhausts stop gaining past 0.400". Im now curious to see where the VQ35 Maxima intake peak is.

From what I've gathered the NISMO heads use the VK45 Ti valves and lifters (34 mm diameter) One Z company offers 1.8mm lifter spacers so you can use normal VQ35 cams but IMO it's a waste of a race head running with a street cam.

 

So the 0.426" lift on my nismo cams directly translates into 10.82 mm lift. Why do all those retarded ***** keep advertising it as 10.5 mm? Thats lame as hell. They sell cams for 1Gs and cant even convert inches into metric. Misinformation pisses me off.

 

The vq35 maxima head was from an 04

 

03 = 04 for all intents and purposes. The only reason they have different part numbers is because the valves springs differ.

 

Interesting

 

Excellent post. I wonder what 350Z heads would flow?

 

The same. All VQ35DE heads are the same except for different valve springs depending on the year.

 

oh cool





123

 

In + free bump for a great post.

 

Aw man, sad to see the exhaust #'s for the pathy heads. And I was firm believer of my pathy/max hybrid 3.5. Time to change minds here.

-Peter-

 

Hmmm...that exhaust port flow has me concerned. Been reading around and it seems as if most engine builders aim for an interport flow relationship of 75%-85%; meaning that's what the exhaust port flow should be in relation to the intake port. I wonder if an oversize exhaust valve would help this...hmmm

 

it WOULD, but i dont think it would really make a large difference, since i would think the majority of flow characteristics are from the actual insides of the head, the size of the port itself probly has a smaller effect than, say, the inner cross-sectional area. boring the exhaust (channels? lines?) would likely give you a much better outcome than simply a larger valve and accomodating seat.

that said, every little bit helps

 

I wouldn't worry about oversized valves because of the expense, but had someone posted this head flow data a year ago before I did the VQ35 swap, I would have ported the exhaust ports.