mg_ls1ws6

Hey newbie here but was wondering what's a good cam for a dd high elevation (5312ft) to be exact ?

hrcslam

A boost cam with some boost.

Other than that, what do you want from your engine? It is just like selecting a cam at low elevation, it'll just make less power. You could get away with more aggressive valve events that raise your DCR, but you'll have to be able to get at least 93 Octane (not likely), and never drive in low elevation or DA's or have a dead nuts tune for knock retard....

mg_ls1ws6

Thanks for the info I'm just trying to get a good street cam that's not to aggressive and makes good power its my daily driver and I'm thinking about spraying for when I play around on the weekends

hrcslam

What is good power? What mods do you already have? What engine and vehicle is it in? Manual or auto? Rear gear ratio? Tire size?

My opinion and your opinion of what good power is differs. Are you looking for a high revver? Or something with great low end torque? Maybe something in between? Goals for RWHP, 350-400 or 400-450? Maybe more?

You should make a sig that has all your vehicle information, this way when you ask a question like this one we all have most the info we need already.

HCI2000SS

iTrader: (2)

Like mentioned above, more detailed information would be helpful

mg_ls1ws6

i was thinking good power would be 400-450 hp i want the Cam to be in between low end and a high revver its a 02 ws6 ls1 with Lt headers a catted y-pipe and a borla adjustable exhaust and a slp lid its a manual with the stock 3.42 gear ratio the tire size are 275/40-17 and front and back

hrcslam

Do you need to pass emissions? Also are you planning on a gear swap?

mg_ls1ws6

i do need to pass at least a visual emission test can i be tuned to do that ? and yeah was thinking 3.73 or 4.10

.boB

iTrader: (1)

The only real issue with high altitude is a lower ambient air pressure. As you already know, you lose 2-3% per 1,000 feet. A lower ambient air pressure means that you will have a lower cylinder pressure. Kind of like losing a few points off your static compression.

You will lose low end cylinder pressure if you install a big cam with lots of overlap. The opposite is also true. You want to keep overlap to a minimum, and yet still have enough lobe duration to fill the cylinder well. To obtain that, look for a wider LSA.

Also, the sooner the intake valve closes, the greater your dynamic compression will be. Be sure to read the cam card for that information.

mg_ls1ws6

thanks for all the info guys so do a think a nice mild cam with high velocity ported heads would be good ?

hrcslam

Yes, that'll do you good. You should hit that with ease. I'd talk to Martin @ Tick or someone that specializes in LS1's personally if I were in your shoes. I'd ask for the biggest cam I can do that will still pass emissions easily, and give me a nice broad power band peaking under 6500rpms. Then build the SCR to match with head gaskets; if head gaskets aren't an option, then make sure your cam builder knows that.

If you're getting ported heads then head gaskets and milling can get you the best SCR for your needs. For emission reasons you don't want to go too high with your SCR as that will limit your cam choices.

That should result in a nice daily driver and small cam. With good ported heads and your existing mods plus a good tune, SAE corrected 400rwhp should be easy.

Sales@Tick

iTrader: (3)

Give this man a medal!

I explain this to all of my customers at altitude. Air has mass. Higher density altitude means less available air mass. Air can be compressed. When compressed it makes pressure. The more mass you have in the cylinder when it is compressed the more pressure it makes. Thus a bigger, or smaller bang.

Thus the valve events must be compensated for when a camshaft is specified for an engine running at higher altitudes.

mg_ls1ws6

Thanks guys for all the help and info I learned quite a few things I didn't know I'll let you guys know how things go 👍

mg_ls1ws6

Thanks @hrcslam

hrcslam

This is true, however depending on the location, density altitude can fluctuate dramatically throughout the year or day(think Southern Arizona). If I built a daily driver to be awesome in Tucson in the summer with 6000+ DA, I'd blow my engine in Phoenix in January with <1000 DA.

This is why I made the statement the way I did. If you're in Colorado where your DA is over 5,000ft year round there's really no worries other than don't take it to Disneyland for your summer vacation. But, when someone can go from 6000ft DA to 1000ft DA (or less) in a few hours (Show low to Phoenix), you'd want to cam it for the lower density altitude and deal with the power loss like everyone else.

I don't know his actual location so I gave the advise I did because lurkers read this too and if they live in an environment similar to mine then they don't want to cam it up for high DA.

Sales@Tick

iTrader: (3)

I think it's a bit dramatic to say that the engine would blow.

Too much emphasis is placed on DCR solely. It is just part of the combination. Is it good to attempt to optimize it somewhat? Sure, but don't build the combination around it.

DCR changes as RPM changes.

hrcslam

I agree. DCR is a tricky subject and often misunderstood, the calculations used don't take into account that the air mass is moving. And it's moving at different velocities depending on rpm and intake/exhaust set ups. But, DCR can be used to get the engine within certain perimeters, just like SCR can.

I'll use my build as a comparison. I have 11.52:1 SCR with my IVC @ 68° ABDC (.002") I get a DCR of 8.93:1 and 187 psi cranking pressure at sea level. At 6000 ft I get 7.72:1 DCR and 152 psi on the exact same set up. If I set up my cam to give me 8.93:1 DCR at 6000 ft, then that set up at sea level would put me at 10.13:1 DCR. Considering that I drive to Phoenix occasionally and Phoenix get's DA's below 1000 ft (winter) while Tucson gets DA's over 7000 ft (summer), I had to take this into account.

Funny thing here is I've done compression checks on my engine to find my cranking PSI is over 185 psi dry at 6000+ DA; 220 psi wet. I wonder what that means? (Seriously, what does that mean?)

If I was still living in Colorado Springs I definitely would've gone a different route with my cam though. As I would never see DA's below 5000 ft. I think the same would apply in most of Wyoming, Colorado, Utah, New Mexico and maybe a few other states too.

I guess I'm saying I agree with you, but would take more caution in regards to location with DA's as some places vary wildly while others are more consistent.

And it may be a bit dramatic, but not everyone can re-tune their car for DA like we can, so it is a very real possibility.

.boB

iTrader: (1)

Thanx! I live at 6,200' ASL, and rarely race below 5,000'. I'v had to do some home work to build a good engine.

I think this is also true. I get good track performance without engine damage because I'v built the engine to perform at about 5,000'. When I drive to 11,000', I do lose some power like everyone else. But it still performs well.

Air density around here can change dramtically in just a few days. Last Saturday at the track it was over 100*, and dry. Yesterday it rained all day long, and didn't get over 60*. On a day trip, altitudes can vary from 5,000' to 12,000' in a few hours.

Last year I went to MoAb, UT. Lower in altitude, and it was really hot. Like Africa hot. There I ran E-85, and the car had no troubles at all; no detonation, and no overheating.

hrcslam

So maybe the best way to build a cam for elevation is to find out the max you can get away with at the lowest DA it will be running in and build around that? So your you it's 5000ft DA, for me it's <1,000 ft DA. Which really sucks cause most of the year I'm over 3500ft DA.

.boB

iTrader: (1)

Yeah, that's pretty much it. Just like the manufacturer, you design for the worst case scenario, and then it lasts forever. At 3,500', you'll lose about 10% of your power. But that's 10% off the top. Unless you're racing, you won't really notice it.