Alternate cam timings settings opinions?

[jmgtp]

I don't think there is a thread that covers all the options, what they do and how they behave. Maybe I just can't find it.

I guess I'm looking for a change so I'd like to hear others takes on different settings. I've been running the -13* on the exhaust cams. It does help it breathe up top but there is a low end sacrifice and a bumpy idle. I do plan on driving it daily in the summer and I think I'd prefer a bit smoother idle and a more off idle torque even if at the sacrifice of some top end power. I think it causes worse fuel economy and must dirty emissions up some. I was getting about 18mpg with a mix of city/hwy but I did drive it very aggressively.

I'm interested in the +6 intake / -6 exhaust. I imagine there still must be some kind of hit to idle quality but from what I read it sounds like mid and top end power have an increase and no loss to low end torque? Is this accurate? Impact on fuel economy? Emissions? Can anyone elaborate more on the behavior of the +6/-6 compared to stock timing, compared to the -13* timing?

Any other combination's that anyone has tried? What happens when you retard or advance both intake and exhaust? In other words what would happen say if both the intake and exhaust cams were retarded 10*?

My car is a 5spd so the loss of low end torque may not be as noticeable as would be with an auto. I have 96 intake manifolds, a custom plenum tube with 75mm throttlebody and full 2.5" exhaust - all things that help with top end power which is what I crave but what I need is some better low end driveability. I really like being able to wind it out and make usable power at high rpm - but I'd give up some of that for a bit more driveability.

[jmgtp]

there is a thread on teh 6/6 not too far down (http://60degreev6.com/forum/f99/6-6-timing-t42446)

one post says:

if that means advancing intake cams 6 degrees, and retarding exhaust cams 6 degrees, what you are doing is closing up the lobe separation angle of the intake/exhaust events. The creates more overlap, more scavenging effect, bleeds off a little compression, and less vacuum signal at idle.

If it means the opposite (retard intake/advance exhaust), you are spreading/widening the lobe separation angle- more vacuum, less bottom end, more top end power, more rpm capability

typically the factory widens the LSA if using a lot of duration, to get some semblence of idle quality back- tight LSA makes an engine idle rough and get lousy gas mileage

+6intake/-6exhaust you lose some vacuum and gain some scavenging, which I imagine should increase top end and be detrimental to idle / low end torque.

and then it states -6intake/+6exhaust, you gain vacuum but lose bottom end and gain top end?

are these statements correct? when the +6/-6 is referred to which case is it? I believe it to be +6 intake and -6exhaust.

[HayesPerformance]

Well, I did the 6 advance intake / 6 retard exhaust.

You Gain top and bottom, pulls MUCH harder, better MPG, better idle, I would HIGHLY RECOMMEND IT!

[jmgtp]

Sounds like this is something I need to try. Has anyone actually dyno'd any of these?

I have the adjustable cam timing tool from a production run that was done some time ago. It basically has two adjustable levers and is indexed. In other words you set the crank at 0* and use the tool to lock the cams down advanced or retarded - makes it easy to get the timing you want and be consistent between banks. It has been a while since I've used it and I can't remember if the indexing on it is in cam degrees or crank degrees. I believe it is in cam degrees, so for example if I wanted to change the intake cam to +6 crank degrees I would need to set this tool to +3. Does anyone know for sure if the indexing marks on the tool are cam or crank degrees? If there is any question as to which tool I am referring to I can take a pic next time I'm at the garage.

I'm assuming that the +6/-6 is in CRANK degrees and not cam degrees.

[HayesPerformance]

Thats right, on the tool +3, -3 and your done.

Then use the timing tool locked in that position as your cam hold down tool to do the timing procedure on the engine.

[jmgtp]

Thanks for the replies.

I think I'm going to change the cam timing this weekend. I just need a more solid idle and better low end torque if I want to drive this thing daily, better mpg will be welcomed too.

I think I'm going to stray a bit from the 6/6 - I'm still biased toward top end. Maybe something like advance intake 4 and retard exhaust 8. Not that dramatic of a change from 6/6 I suppose but I think that should still bias it a bit more toward the top end. Still open to ideas.

It was 190whp a few years ago on a Mustang dyno with basically a cone filter, flowmaster mufflers and -13* on the exhaust cams (it had a power robbing ~10:1 a/f on the wideband too, which I soon after discovered my fuel press exceeding 60psi!).

Since then its gone through some changes. I have the hardware for a screaming motor now (96intakes/ported heads/75mm TB/2.5"exhst/5spd) but its just not running as strong as I think it should be, this thing should be able to move some serious air - granted its not tuned right, but still. With all the additonal work done I think the buttdyno dictates maybe 200whp which is just not where I want/thought it to be.... I've had thoughts lately of giving up and buying a GTO - but I can quickly dash those aside and remind myself I'm saving for a house.

[mrl390]

Would the 6/6 timing work on the 96-97 motors? Something I might try when it comes time to replace the timing belt.

[jmgtp]

I believe the design of the 96+ cams have the exhaust valves retarded more than the prior generation so the 6/6 would have a different impact.

[jmgtp]

Retimed it with what should be +5 intake / -7 exhaust.

Much MUCH smoother idle. Bit more low end torque and a flatter feeling curve. Did lose a bit in the upper range but I guess you can't have it all.

[pocket-rocket]

Imagine how it would have felt up top with your old intake, lol. I don't mind the 13* still. It sets my car apart from others at stop lights idling like that, but it did ruin my cat. The catalyst had gotten knocked loose from the idle, so I took it off and hollowed it out.

[OldSkoolGP]

I originally ran +5/-5 and liked it, but I did that with a degree wheel with the engine out of the car. Once I got the tool the most accurate thing I could do was +6/-6, but I still like that. I personally think the engine idles smoother than stock with that setup, the the torque curve is so much flatter I think it's the best anyone has come up with so far.

[jmgtp]

I don't even remember what a stock idle feels like.. haha. But I can say it is so much smoother than the -13, but still a tiny bit rough. The torque curve is definetly flatter, which most people would like but I gotta say I kinda miss that 'flip of the switch' power that used to come on at 3500rpm and the lopey muscle car soundling idle. But what weighs in more heavily for me with the +5/-7 (and yes I used the indexed tool) is the vastly improved idle quality and low end torque. I've been driving the car daily and the -13 was good for power up top but miserable as a driver.

[pocket-rocket]

I wonder if the newer intake makes that much of a difference. I mean, mine drove fine with the 13* and I have the old style intake on it. Mine didn't really feel like a flip of a switch type thing, but it did start kicking in at a fast rate around 3500. Then again, unless I am on the highway or on a long strait around 50-55 mph, I would always keep it around 3k rpms.

[jmgtp]

It was probably the intake manifolds and cam timing together having that effect. The intake manifolds have been on for years now. I think I was in my 2nd year at UConn when those went on so that would be ~7 years ago. I don't remember at all what a STOCK dohc car drives like! haha. I've only been in 3 dohc cars ever too... a 92z34 auto that was much faster than I thought it would be, a 95 gtp that was slower than an office chair and my gtp.

But yes, with the 96 intakes/-13* timing in my experience around 3500 rpm would be the wake up zone. It would be really noticeable if you were lugging the engine a little bit and then crossed over into 3000+ rpm it would snap out of it, start sounding meaner and building torque. I'm still getting used to this flat torque curve.... I always expect that snap at 3500.

[HayesPerformance]

so -13* is best in with the 5spd?