I spent a good deal of time searching around and can't seem to find what I'm looking for so please don't have a hissy fit if this info is posted somewhere and point me to it!

My question is; what are the highest lift/duration cams I can run with stock heads + double shimmed HR valvesprings? I've seen that some of the higher lift cams require clearancing and considering how well our heads flow stock I'd like to do without any machining to save a lot of cash (at least for now). My current understanding is that around 272/272 with 11.5mm lift is the most that would work with that setup, and those may even be overkill for a stock bottom end N/A build. Please correct me if I'm wrong.

Also, does anybody have some basic info on what kind of powerband I'll see - mainly where it'll peak, and how far out it will make power - with various cam durations/lift? Just assuming a relatively free-flowing IM and no head porting as givens (and likely restrictions).

I'm guessing going with the highest lift I can work with, and the lowest duration that will make the powerband I want is the best way to go, correct? As I understand, upgrading rod bolts, a revup oil pump, and of course valvesprings should make a VQ35DE safe for around 8000RPMs. Of course making power anywhere near that high is another story. I'd be happy with a peak around 65-6800 and redline in the 7600-7700 range. I'm not sure how my current IM will flow that high as there has been ZERO testing of it aside from on a stock engine and stock revs with a mismatched LIM but that's discussion for a different thread.

Thanks for any input!

 

Get an HR spring and get it bench tested. The rate is good to 8k with stock valve/retainer you just have to figure out where bind is, I have heard 12mm. As for cams this is a great read:
http://compcams.com/Technical/FAQ/Ca...eQuestions.asp
Read whatever you can off that site, although not Z specific it will give you a much better idea of cams.

 

Thanks. I have a good idea of how they work and that is a decent read, but I am looking for VQ35 specific information in terms of curve shape with different duration/lift options. Although I don't want to over do it, I also don't want to end up with something too mild and end up wishing I'd gone bigger.

Right now I'm really considering the Kelford stage 2 N/A cams (280/272 with 11.5 lift) or something more mild like JWT C2 (261/261 with 11.5 lift).

 

Generally more duration and less lift for N/A. The tomei's are nice N/A cams the bc grinds are somewhere between fi and N/A but work well(mine made good torque), jwt has cams to suit any need, haven't seen a build done with kelfords, and the cosworth cams are documented by them so I am skeptical but on paper look good for N/A. Dyno information is out there and making this decision is exhausting. good luck.

 

It sure is. Is there any reason why you would want less lift with N/A? I can see N/A not getting as much benefit as you're not forcing air in, but extra air is extra air. More lift = more CFM on a flow bench, and more CFM means more air manages to get in during the intake stroke at high rpms no doubt.

Cosworth cams are also really expensive compared to the other options. Tomei has sooo many options I can't imagine calling them F/I or N/A, since you can choose the exact numbers you want for either, and even order intake and exhaust cams separately. It seems that Kelford has the idea for N/A cams to go more agressive with intake than exhaust, so if I do end up with Tomei it may be a consideration to go slightly smaller on exhaust cams.

 

It has to do with cylinder filling if the valve isn't open as much velocity can be maintained. With FI you have positive manifold pressure and the air is pushed in rather than sucked. This isn't overall lift its lift in relation to duration. But if you want full out race cams then its out the window.

 

I don't necessarily want full out race cams, but I really don't want to sacrifice topend for bottom end/driveability. In the same respect, I don't want to kill midrange power for a little topend gain. From looking at your dynos and some other N/A 3.5 dynos, around 264 duration is a pretty good point for keeping a solid midrange/bottom end. I may just go with tomei since there are so many options, and probably 268, maybe 272 duration with 11ish mm lift. The Kelford S2 cams may be a little too big for a 3.5L application.

I've also decided that if I'm going to install cams/valvesprings anyway, that it will be worth the investment to send my heads to M2racing for a full porting and valvejob. I will also spend some time porting my IM, especially around the bends where it seems to be the most restrictive. I really want to get past the normal VQ35 6200 peak and sharp dropoff.