I've been searching and reading for a couple days now, and I KNOW that I read awhile ago a thread discussing cam adaptors for a 3.0 -> 3.5L swap that had some of the VTC advance "built in" but I can't seem to find it now that I need to.

So I guess I'll just bring it up again, and maybe get flamed in the process lol.

If I understand correctly, 0* advance on the 3.5 with the 3.0 sprokets would occur if the dowel hole is redrilled 180* from original, correct? so for 15* advance the new dowel hole would have to be redrilled 165*, 20* would be 160*, so on and so forth? I'm just looking for confirmation really, I'm in the middle of my swap and kinda want to experiment with the cam timing but would hate to have them drilled incorrectly of course. Probably will go the adaptor route rather than spacers/redrilling simply for the swapability factor.

 

Sounds like you've got the gist of it but don't forget about the 2:1 ratio between the crank and cam. So if you want 20 degrees advance dialed in for example, you're only measuring out 10 on the cam/sprocket.

Here's a thread where I posted what I did to set cam timing:

http://forums.maxima.org/showthread.php?t=408192&page=2

 

This is why I shouldn't ask questions at 2 AM lol. I forget simple stuff, or just plain don't think about it hard enough. Thank you for the link Dandymax, I hadn't seen that one before, but very helpful. Somewhere in the discussion it was mentioned that Stephenmax's adaptors set valve timing at 10* overlap, did I catch that right? 2* should be stock overlap with fully retarded VTC's. and IIRC they have a 30* sweep? so 32* overlap would be fully advanced VTC's. Which I'm assuming probably wouldn't idle worth a crap.

I like your machined sprocket idea, very cool. It looks to me though that you stuck with 180*? Or is that just an illusion? What did your timing advance end up being?

What I'm aiming for is something set in the middle of performance and drivability with a few steps towards performance. I have no FI nor spray, the car won't get any traction in 1st even with the 3.0L in it. I have an LM1 wideband, but no EU or any piggyback yet. I won't mind if it's lopey at all, and I really don't mind if it loses a little at low RPM obviously, hoping it might hook up (pipe dream until I get ahold of a LTD Slip). I'm thinking about trying 18-20* advance but obviously don't want to be pulling the timing case again because it won't idle at all. Just want some ideas before I arbitrarily pick a certain setting to start.

 

That was me that got the set that were advanced slightly on the intakes, if you search posts for my username in the all-motor with keyword: intake timing it should come up, and there is two threads, one of them has the specs. To tired to do it for you. But anyways, PM me if you want those spacers, I'm going full swap and have already stripped/parted out my other motor and have those adaptors still. I'm not sure if that's how he cuts all of them now but re: feedback, I swear my car pulled harder up top than it ever should have with a working VI. (Yes, sorry, I know I know, that says nothing, lol)

 

They can sweep up to 40* mechanically but you might have driveability problems at off idle/low rpm and/or have troubling idling at stock 4th gen ECU rpm settings with 30-40* of overlap. Last I knew his adapters had 12* of advance. So unless he's changed them that would make total overlap 14*, which is a decent compromise for low/mid range performance without a horrible idle, but trades off against top end (where you'd want more retarded timing).

That is an illusion, the slot is clocked 2* on the sprocket. I wasn't running stock 3.5 cams though (different lift/duration etc) so just knowing the advance alone won't mean much to your application. I would suggest you figure out what cam timing you want (ie the centerline and resulting openings and closings), then calculate the amount of advance required to achieve it.

Do you have a 5-spd? With a MT and stock 3.5L cams, and for high-mid/top end power (say 4500+ rpm) without huge lope at idle I'd probably set the centerline somewhere around 117-121, (ie 4-8* of advance, giving 6-10* overlap). Stock 3L cam overlap is 6* but keep in mind the 3.5 lift is a bit higher. If you want to bias the power band more towards the low/mid range use the more advanced end of the range (lower # centerline, or go even further to 113-116), but if you want top end use the more retarded end of the range (higher # centerline, less advance).

 

According to a PM he sent me a while back he was dialing in 15* of advance presumably (on my end) so the IVC would remain the same @ 49* ABDC.

 

I keep hearing too many different things, I don't know what's current anymore. As of last June/July it was a 12* advance resulting in a 113/112 centerline. At that time he specifically mentioned to me that was his usual standard.

Bottom line, contact him directly if you're considering his adapters ("you" as in whosoever might be thinking about them)

 

That yielded the thread I was searching for originally! Thank you KRRZ350
http://forums.maxima.org/showthread....+intake&page=2
I may yet PM you on the adaptors, I was planning on doing something similiar to Dandy Max's setup after seeing that, however time may become an issue.

DandyMax, Yes I have a 5spd. Although the idea of an absurdly lopey Max is appealing, I agree that it may not give the best performance if I only get power 6k+ . So retarding the centerline 8* would give me 10* overlap which is less than the 14* overlap the Stephenmax's adaptors would give or is that 14* given in crank angle? Which makes it 6* retarded?

Forgive me for all the questions, I'm coming from a OHV background, and the ability to actually change your centerlines independently is completely new to me. I think I'm catching on...

 

Not to mention you may have trouble with driveability without some decent engine management..

If you're talking about advance and retard and overlap it's always crank angle, since the angular references are with respect to TDC or BDC. I think you meant to say advancing the intake centerline 8*.. (ie 125* ATDC-8*=117 ATDC, the exhaust stays at 112 BTDC) but yes, that would give you 10* of overlap vs 14*. As I mentioned in the last post, I expect you'd be gaining a bit of top end while giving up some low/mid range. It's up to you, where you want the powerband...

 

EU is in my future. No worries however, it probably won't be another couple of months. I'm balancing the Max, an XJ, and a dodge truck resto as projects so the play $$$ gets spread thin ussually. I have automotive A.D.D. can anyone tell? I got tired of messing with the XJ for the past few months so I used a leaky waterpump as an excuse to do the 3.5 swap

Ok, back on topic...

Ok I may have found my confusion. It has always been my understanding that Advancing a cam would move the powerband down in the rpm range, and retarding the cam would increase top end power. The same with overlap. The more overlap you had the more the engine lopes at idle, or the rougher the idle, and the scavenging effect would come on in the higher RPM's to bring on the power. You're saying that if I advance the intake cam that I'll gain top end, while decreasing the overlap?
This is why I'm asking lol. I've always known cams with more overlap to produce a higher powerband. Am I missing something? Or does this have to do with the fact that the exhaust am isn't being changed along with it? Of course that would just make a wider LSA, which doesn't make sense to me why that would make more power up top?

 

In general that's true, yes.

I'm not saying absolutely, but comparatively. They are both advanced from the stock centerline, and so will move the powerband down. But compared to each other, the less advanced setting (giving 10* overlap) will likely result in a bit more top end at the expense of some low/mid as compared to the more advanced setting (giving 14* of overlap). It's not so much related to overlap and nothing else, it's mainly the valve events that are important (which are of course also related to the durations). For example, by running the more retarded setting (comparatively) on the intake your closing is later, which allows high rpm inertial effects to be utilized. You don't necessarily need a lot of overlap at high rpm, although you do want some if the header/resonant frequency tuning is matched to the cam. If overlap gets excessive at high rpm (either too early an IVO or too late EVC) you can actually create over-scavenging and pull fresh charge out of the cylinder.

 

OK, that makes sense. So the entire theory here is that the norm is advancing both cams to move the power band down, and by actually advancing the intake cam LESS than the norm you're keeping some of the high end power that would be present had both cams been at the stock 3.5L centerline. So in theory if the exhaust centerline was at 112* BTDC, and the intake centerline was at stock centerline (which does anyone know VTC's fully retarded?), the engine would make gobs of high end but barely idle. The VTC's accounted for that by advancing the cam during lower RPM to help driveability, correct? Or am I close at least lol?

 

Close..

With the VTC's inactive, the centerlines are 125/112. That is a relatively retarded intake setting with only 2 degrees of overlap, so the car idles great and has some top end power, but the midrange and lower end driveability will be poorer. The FWD 3.5's do not have any exhaust VTC, you're fixed at 112. But with the VTC's operating the (intake) cam gets advanced in varying amounts from just off-idle to around 6k rpm where it goes back to retarded.

See this thread, particularly page 2 has some good graphs showing advance angle vs rpm:

http://forums.maxima.org/showthread.php?t=357173&page=1

But of course, if using 3.0 timing equipment, you're losing VTC control which means you have to pick one static cam timing that will best suit the type of overall power band you want (since it's not changeable on the fly anymore). You can't change the exhaust easily because of the dowel location, but the intake can be changed quite a bit if desired.

 

Awesome, great info! I knew the exhaust cams were static, thank god I don't have ANOTHER cam to mess with

But for the sake of arguement. Why would you not be able to change the exhaust centerline the same way you did with the intake? Assuming I keep the timing at 112* for the exhaust side do I even need to use an adaptor or do machining, or could you just reverse the timing mark since there's no cam sensor involved?

My new motor (02 vq35DE) was supposed to be delivered today, I've waited patiently all week. Alas a motor was delivered... A pristine 32K mile VQ30. BAH! I already have 2 of those. Wasn't even a DE-K, which I might have just kept had it been. I was HOPING I could at least dig into the timing equipment tonight to see what I was dealing with, but no such luck. SO, I'm still in the dark waiting till Monday when they bring me the right one. So bear with me if it's obvious why the dowel is an issue on the exhaust side, I've just never seen it My April 6th deadline is looking alot closer now. but it gives me more time to ponder this, lol.

So full advance would make the centerline 109*? full retard at 125*. Hypothetically if I set intake cam timing to 125* the car would be stronger at top end but idle crappy. Set at 109* idle would be smooth and lowend would be strong. Makin sure I got this right.

 

You don't need to remove or move the dowel pin on the exhaust cam. You just need a spacer because the end of the 35 cam is slightly shorter than the 30. The dowel pin is long enough to go through the spacer and into the exhaust cam gear.

For the intake cam, once you figure out where you want your timing to be, you can cut up a vq30 valve to use as a longer dowel. It's 6mm.

 

As 95naSTA mentioned, you only need a spacer for the exhaust if you're not changing the timing. This will all become clearer to you I'm sure once you have a chance to physically look inside your timing cover. The dowel on the exhaust cam is in the same position on both the 3.0 and 3.5 cams/sprockets, which is why the exhaust timing can't be changed going the adapter route (since you'd be essentially drilling two holes into each other). Now having said that, if you want to change the exhaust timing, it can be done via what I did on the intake side... rotate the sprocket 180 degrees and machine a new slot that's offset by the angle of advance or retard (and you need the spacer of course).


How are you calculating full advance? The VTC's can sweep ~40* at the limit physically. But you'll have the ability to set the intake centerline to whatever you want if you're getting an adapter made for you or machining spacers/sprockets like I did. Yes a centerline setting of 125 will give better top end past 6000 rpm, but it will idle smoothly, because the overlap is almost non-existent (with stock exhaust timing at 112). With a lot of intake advance it's the opposite... lopier idle and good low/mid torque, not so good up top.

 

In summary, IVC > overlap as far as these motors are concerned.

 

I would tend to agree, as the evidence to-date does seem to suggest it (plus what I've seen doing detailed engine modeling). The ports are decent flowing, fairly high velocity (for factory heads) so not as much overlap needed as on say, an old school push rod engine with 2-valve heads.

 

Makes things simpler.

I was using the 32* advance mark on the VTC sweep charts in the other thread. Just as a reference. I guess that would be full sweep on the stock ECU. not necessarily the mechanical limit. And now that I'm looking at it again even with 32* it should be 93* centerline? I divided it the first time.

OK...that does make sense. I was trying to justify the lopey idle with less overlap and turns out I was just thinking about it incorrectly lol.

I've been learning this, albeit slowly. Thank you guys for your help with this. You've helped alot.

 

Just to throw some more into the mix, what would you expect if you advance the Intake centerline to 121* ATDC and retard the exhaust cam to ~118* BTDC to keep somewhat of a tighter LSA, Hopefully increasing top end even more? If I were to do this I'd probably go a little less. Somewhere around 119* intake 116* exhaust. Has anyone had any experience messing with the exhaust CL as well?

 

To my knowledge no one has changed exhaust timing. I'd have to check back to see what I did with the scenarios when I was doing modeling (ie how far from stock I changed it) but I have a feeling you may be getting a little too early on the exhaust there at 118. Around 110 (slightly retarded) or 112 seemed decent but then again the cams I was primarily modeling had a lot more duration, and I don't recall right now if I experimented with changing timing on the stockers since I knew I wasn't using them. I'll try and take a look later at home. With stock 3.5 cams you might not be too bad around 119/114-116.

 

If you could, that'd be awesome! What are you using to do the modeling if you don't mind me asking? Just curious.

 

Hold on a sec, I was at work earlier and not really paying too much attention (sorry).... but I just read this again and you're talking about advancing the exhaust, not retarding it, if you're moving the C/L farther away from TDC (ie bigger number). I edited my original post (#21). If you're looking to retard the exhaust a few degrees then you'll be thinking in the ballpark of 108-110 BTDC. Still gotta look back at what I did for the modeling. I was using EAPro 3.5.

Edit: I checked and I didn't model stock cams, sorry.

 

I caught that too. I really am understanding all this better now, however typing it all out is obviously difficult for me. IE I can see it in my head, but then I try to put it on virtual paper and BLEH. All over the screen. Anyways, you're right, I said retarding, but put the numbers in wrong. I really have to figure out what I'm doing with this by tuesday, supposed to drop off the sprockets at the machine shop. Maybe if I thought about this stuff some other time before 2am?

what I was TRYING to say, is retard the exhaust, while advancing the intake, keeping the LSA tighter without having to advance the intake side so much. NOT 118* or 116* on the exhaust but rather 108* BTDC.