Double Roller Advanced Timing?

[T-Mill]

So a friend of mine stopped by when I was in the garage and saw my double roller and started asking me if I was going to advance my timing... I had done a little research and from what I gathered I was just going into it assuming I was going to install it at 0*...

My friend said I should advance it at least +2*... he acts like knows alot about cars, but sometimes I think he's full of **** so I don't really hold stock in anything he says... what are some of your guys' recommendations for timing?

a little background: I don't plan on racing the car or making crazy times... I installed a VS cam, 105# springs, aluminum rockers... the only reason I did all of this was because it was all basically given to me. Obviously I'd like to get the most performance that I can out of it, but I want to balance the performance with drivability since this car will be driven just about everyday and I need the reliability...


edit: also... Hptuners and 97 PCM are on their way

[bigbrian442]

Re: Double Roller Advanced Timing?

Advancing the cam shifts the power band of the cam lower in the RPM range.

[LETZRIDE]

Re: Double Roller Advanced Timing?

I believe I read that it also increases compression a little? I have been considering advancing the timing myself, but I need to do alot more research on it first...will be interested to see what else gets said here...since I was gunna make a thread about it soon anyways...

[Choppers]

Re: Double Roller Advanced Timing?

I personally wouldn't advance the timing. Thats just me.

[Pewter02Camaro]

Re: Double Roller Advanced Timing?

I believe I read that it also increases compression a little? I have been considering advancing the timing myself, but I need to do alot more research on it first...will be interested to see what else gets said here...since I was gunna make a thread about it soon anyways...

You can not change Static compression without changing chamber volume or the piston, ie dished or domed. an example would be when you mill a head down compression increases because you are making the chamber smaller. if you go wish a piston with a bigger dish you reduce compression because you add more volume.

T-Mill, Check the cam card that came with your cam, you may find that it already has timing added to it, many do.
It would be next to your degree open number. 206/216 at .050" these should be your degree specs. If it looked like this"206+2/216+2 at .050" on the card it would already be advanced 2 degrees.

Brian i know you can correct me if i'm wrong, LOL

[LETZRIDE]

Re: Double Roller Advanced Timing?

As I understand thing, your compression ratio actually changes as you are driving the car...turbo charged cars under boost actually go wayyy up in compression, I think it was like 20 or 30:1 or something crazy like that.

By changing the timing you are changing the events that are happening in the cylinder, and therefore you can actually increase compression.

I'm remember reading something about this like 2 days ago when I was researching my heads etc...I have to go to work in a few so I don't have time to find it until maybe sometime tommorrow...I'm positive it talked about increasing compression...but I believe there are two types of compression, static, and something else...so it was hard for me to understand...

[Pewter02Camaro]

Re: Double Roller Advanced Timing?

As I understand thing, your compression ratio actually changes as you are driving the car...turbo charged cars under boost actually go wayyy up in compression, I think it was like 20 or 30:1 or something crazy like that.

By changing the timing you are changing the events that are happening in the cylinder, and therefore you can actually increase compression.

I'm remember reading something about this like 2 days ago when I was researching my heads etc...I have to go to work in a few so I don't have time to find it until maybe sometime tommorrow...I'm positive it talked about increasing compression...but I believe there are two types of compression, static, and something else...so it was hard for me to understand...

You are referring to dynamic compression.

Static compression does not change unless volume changes.

Wikipedia has a decent explination of both.
http://en.wikipedia.org/wiki/Compression_ratio

[cam98aro]

Re: Double Roller Advanced Timing?

As I understand thing, your compression ratio actually changes as you are driving the car...turbo charged cars under boost actually go wayyy up in compression, I think it was like 20 or 30:1 or something crazy like that.

By changing the timing you are changing the events that are happening in the cylinder, and therefore you can actually increase compression.

I'm remember reading something about this like 2 days ago when I was researching my heads etc...I have to go to work in a few so I don't have time to find it until maybe sometime tommorrow...I'm positive it talked about increasing compression...but I believe there are two types of compression, static, and something else...so it was hard for me to understand...

ill make it very simple:

changing cam timing will change the points of when the valves close/open, when you change the timing you are keeping the valve that used to be closed open for a bit longer, and it causes a bleed off in the cylinder.

its the exact reason why putting a bigger cam in an engine can let you use a bit lower octane fuel than is required.

for example, i have an engine with 12.5:1 compression, it has a fairly big cam with a long duration, if i retard the timing a bit i can run 89 octane in it with no knocking.. this is of course not putting a load on the engine or driving it, but the same difference applies.

[ssms5411]

Re: Double Roller Advanced Timing?

I wish I knew what mine was installed at then I could tell you, since I'm running the VS cam. I might install my double roller here soon so I will be able to see what the timing was set at.

[techsan23]

Re: Double Roller Advanced Timing?

When I installed my double roller I held the old cam gear up to the new one to see where I should put the magnet. The stock cam gear has one hole for the magnet, and the double roller had several. I put it in the hole that was closest to where the stock position was, but it was slightly offset to one side. A case relearn is a must so the pcm can relearn the new variation between the cam and crank sensor. You can add and pull timing via hp tuners affecting when the plugs and coils are firing, but when you move the cam gear to a different keyway you are physically changing where the cam will be in relation to the crank. I would guess the outcomes of doing this would be different given the cam.

[T-Mill]

Re: Double Roller Advanced Timing?

T-Mill, Check the cam card that came with your cam, you may find that it already has timing added to it, many do.
It would be next to your degree open number. 206/216 at .050" these should be your degree specs. If it looked like this"206+2/216+2 at .050" on the card it would already be advanced 2 degrees.

Brian i know you can correct me if i'm wrong, LOL

I was under the impression that if the card had the +2, it meant that you were supposed to install the cam at +2*? Maybe I'm just confusing myself lol

[Bandit127]

Re: Double Roller Advanced Timing?

Its just a notice to make sure the installer new that the cam is ground with the +2 degrees already. That way, if the installer wanted to do a +2, +4 etc whatever, he already knows what the cam itself is.

[bigbrian442]

Re: Double Roller Advanced Timing?

Compression does not change, Cylinder pressure does. If you do not degree your cam, there is no reason to advance or retard it. You need to keep a close eye on valve to piston clearance when moving the cam.

Advancing the cam can let you run a larger cam then you normal would.

Read this http://www.compcams.com/technical/TimingTutorial/

[Rob Bell]

Re: Double Roller Advanced Timing?

OK so I have a question since I know really nothing about cam specs: Is it always necessary to degree a cam? I thought you could just install it so the dots on the timing sprockets line up. Or is degreeing only necessary if you want to get a little more performance out of a cam?

Even reading the Comp Cams writeup in Big Brian's post doesn't help me much. I understand the basic function of the cam, but not the intricacies.

[techsan23]

Re: Double Roller Advanced Timing?

Is it absolutely necessary to degree a cam? No. Do most people do it? Probably not. As the linked article states, it is for insuring that the valve opening and closing events are in accordance with the specs of the cam. It will find the centerline of the cam, and tell you exactly how much valve lift you are getting. Ive seen people just degree one pair of valves on one bank. And I have heard of very few people that set up the dial indicators on every valve and checking everything.
http://cranecams.com/pdf/803.pdf