schmendog

iTrader: (10)

I bought a blower cam and it has 0 advance gound in (224/230 .581 .591 114 LSA 114ICL) So naturally when I figured 3 or 4 * advance like most other cams. But then I thought of something and am curious, with a roots blower giving me such a low power band already, wouldnt it make sense to just install it with 0 advance or even retard it, and help even out the power band a bit? Newb here so feel free to educate me!

Fbodyjunkie06

iTrader: (10)

I like to see just about every cam advanced.

To what extent depends on the combination. The cam is the brain of your motor and the roots blower is just the muscle if that makes sense.

schmendog

iTrader: (10)

Yeah it definately makes sense, Its just that as I understand it when you advance the timing, you are setting up the engine for a lower RPM power band, and when you retard timing, you are doing the oppposite, giving up lower RPM power for higher RPM power. So with a roots style supercharger (makes all its power and TQ in the lower RPM range) I figured having a cam that was neither advanced or retarded would help even things out. I might just be smoking crack though.

99Bluz28

iTrader: (35)

Advancing the cam increase the Dynamic Compression Ratio and shifts the powerband lower which will give a slightly better off-idle response. IMO, unless you're running high boost, or plan on spinning the motor to 7k, then 2 to 4 degree would still be beneficial to you.

Fbodyjunkie06

iTrader: (10)

99BluZ28 is entirely correct in his comment.

I would like to see it advanced at least 2 degrees. Your valve events are as follows:

Straight up no advance:
IVO is -2.0 °
IVC is 46.0 °
EVO is 49.0 °
EVC is 1.0 °
Overlap is -1 °

IMO the IVC is too late for a street car like yours and the EVO is not early enough for a blower car.

At two degrees advanced they change to this:
IVO is 0.0 °
IVC is 44.0 °
EVO is 51.0 °
EVC is -1.0 °
Overlap is -1 °

Now we are moving your IVC earlier in the valve events which will bring the peak rpm down a few hundred rpm's and we are opening your exhaust valve earlier with this advance. You have to be able to get the exhaust out to get new intake in, and with a blower it's even more so important to do that.

Here is your cam finally with 4 degrees advance:
IVO is 2.0 °
IVC is 42.0 °
EVO is 53.0 °
EVC is -3.0 °
Overlap is -1 °

I prefer the EVO on this advance, but the IVC is getting a little to early IMO for a boosted car on pump gas. As Bluz28 said advancing the cam will raise the dynamic compression more the further you advance it. This is what the motor "sees" and not the static compression.

I think your cam would work best with 2 to 3 degrees advance for what it's worth and I think you would enjoy it more that way also. That instant torque at 2500rpm is going to be awesome. I don't think it will peak rpm wise until 6200-6300rpm and allow you to shift at 6500rpm or so which is where a stock bottom end boosted street car will like to be shifted. Usable power with a street car is where it's at!

PREDATOR-Z

A maggie is spent by 6200 rpm, this is not a centrifugal. 42 IVC is where I would put it.

schmendog

iTrader: (10)

Love seeing the experts chime in Thanks! So far through input on this thread and some PM's from some other gurus I have 2 votes for 2 degrees and 2 votes for 4 degrees advance. So maybe 3 degrees haha. Anyone else?

PREDATOR-Z

This is not a democracy poll, but hey, it is your setup.

schmendog

iTrader: (10)

I agree, I just like hearing input from others so I can learn a thing or two.

Fbodyjunkie06

iTrader: (10)

I would be a little weary of the dynamic of a 224 intake lobe on a 110 advance and 93 pump gas unless it was run on low boost and lower timing.

Even with lower boost and timing it should make better power with the cam there, and one to two degrees in cam timing isn't really all that much.

3-4* is my vote it's up to you as Pred said it's your car.

PREDATOR-Z

I suspect that shmendog just doesn't want to degree the cam and just wants to install dot to dot. Even if he did so, nothing guarantees him his cam will be at 114 lsa/ 114 icl unless it is degreed.

schmendog

iTrader: (10)

It will be degreed, degree kit was ordered yesterday and a cloyes hex a just set will be ordered soon as well, so that I can degree it. Im a firm believer in doing things the right way, I only asked about not advancing the cam to help myself understand the effects of altering ICL with a low end power band. Just trying to gain a better understanding is all.

PREDATOR-Z

Read 4 stroke cam dynamics. A poll is not gonna teach you anything, just opinions.

schmendog

iTrader: (10)

I think that this thread got off topic a bit with sugggestions of how much advance or retard I should do. I couldnt get a good understanding by reading about cam specs like I have tried so Im hoping someone on here could help me understand my original question.

If you have a power adder that is great for upper RPM range (Centifigul blower etc) but suffers in the lower RPM range, wouldnt you want to advance the timing a good amount to help even out the power band? And if you have a power adder that is great in the lower RPM range but sucks up top, wouldnt you want to adjust the timing so that you can even out the power band as well (no advance or maybe even retard)? Again, Im not looking for people to tell me what to do with my cam, just looking for a better understanding of timing.

Fbodyjunkie06

iTrader: (10)

Yes and no, it isn't just about the power band.

When you advance and retard the icl you are altering the dynamic compression ratio also. Too much advance can create too much cylinder pressure which will create detonation issues unless tuned around or a higher octane fuel is ran.

Retarding it does the opposite which will lose power and lower the dynamic compression.

Instead of just crutching a centrifugal like you are saying with advance you would use all of the cams specifications like duration and lsa to create the power band you want and not just relying on ICL advance.

Same with a roots supercharger, use the other cam specifications to create the power band you want.

The other thing you're missing is the intake manifold and cylinder heads. They will also play a big part and most of the time even bigger part in the RPM range that peak torque and horsepower are made in.

A set of stock cylinder heads and your intake manifold that is apart of that blower no matter what the cam timing is due to the runner length, plenum volume and runner design just won't make anymore peak power past 6200-6300 as Pred Z said.

That is why people will change out from the stock style type intake manifolds on say a nitrous car or a N/A H/C/I car to a single plane so that they can rev the motor higher while still staying in the peak power range of the motor. This is achieved by the shorter runners in the single plane and more plenum volume.

Your intake has long runners and less plenum volume therefore making it limited in the amount of rpm and peak power it can make along with making a lot of usable low-mid range torque.

Pred Z is a smart guy and knows a lot about everything I just explained. If you do a search you will see he has covered all of this information for 5+ years and even longer than that.

He doesn't mean to knock down your ideas or questions he is just speaking from a lot of experience.

schmendog

iTrader: (10)

Thanks for dumbing that down for me, that makes a lot of sense. I guess thats why a change in one aspect of the cam specs changes another, and I didnt really consider compression changes with the change of ICL. I asked hoping guys like you and Predator would answer, so I am willing to devour any knowledge on the matter from you guys. Maybe my first post was worded badly, but I wasnt attempting to justify installing my cam dot to dot or trying to make a poll. The input on how much I should advance my particular cam was appreciated, but luckily Predator was nice enough to PM his thoughts on the matter last week.

Thanks for the help guys.

FRiCK

iTrader: (7)

Anyone have any experience advancing or retarding a LS6 cam for a centrifugal?

SSCamaro99_3

iTrader: (1)

I may be talking out my butt. It seems like these guys are saying advancing or retarding a given cam to crutch the supercharger powerband is Fool's Gold. A roots type will run out of gas as rpms increase not because of the cam, but becasue of the design of the supercharger, opposite for centrifugal. Basically trying to crutch a physics issue.