Predict Cam Characteristics...
- Thread starter NicD
- Start date
-
Sponsors (?)
Is the 347e smog legal? Sounds like a smog legal cam to me.
As a general rule big duration and passing emissions don't go together. Once the overlap gets to the point where it causes a rougher idle (which everyone seems to want) it will be tough to pass.
As a general rule big duration and passing emissions don't go together. Once the overlap gets to the point where it causes a rougher idle (which everyone seems to want) it will be tough to pass.
CoupedUp
Banned
Those specs aren't bad for a "street car".
I would go with a little more valve lift (.550 area) and kept the duration and lsa right where it is. The 185's flow peak around the .550" lift area.
The idle will have a little lope to it, so you will know the engine has a cam, but not at all too choppy.
It will make power from about 1800-5800 and shouldn't have a problem passing emissions.
It sounds like a good street cam to me ... although point specific numbers don't tell the whole story of the lobe profile.
Good Luck
I would go with a little more valve lift (.550 area) and kept the duration and lsa right where it is. The 185's flow peak around the .550" lift area.
The idle will have a little lope to it, so you will know the engine has a cam, but not at all too choppy.
It will make power from about 1800-5800 and shouldn't have a problem passing emissions.
It sounds like a good street cam to me ... although point specific numbers don't tell the whole story of the lobe profile.
Good Luck
If you need to stay smog legal all you can really play with is the lift. However, this may still have an affect on emissions as the ramp rates will probably change.
It may be better to bump to a 114lsa if opening the lift and/or duration? I am by no means an expert though. I am just throwing the idea out to see what others think. I suppose that if going for max power in an emissions legal combo one would have to look more closely at the exact valve timing events, as opposed to the very general duration at .050" and max lift numbers.
It may be better to bump to a 114lsa if opening the lift and/or duration? I am by no means an expert though. I am just throwing the idea out to see what others think. I suppose that if going for max power in an emissions legal combo one would have to look more closely at the exact valve timing events, as opposed to the very general duration at .050" and max lift numbers.
Cobra4075
Founding Member
You could put a higher ratio rocker like 1.7's to get a higher lift. I have a custom cam i just took out of my stock block 302 w/ afr's. The lift was around .580 and i didn't have clearence issues. Also, it would not come close to passing emissions no matter what i tried.
there is a formula to figures out how much lope u will get out of it
intake [email protected][email protected]/4-LSA*2
In figured that cam up and comes out to a negative #(-1.5) so u prolly wont tell much diff in idle
intake [email protected][email protected]/4-LSA*2
In figured that cam up and comes out to a negative #(-1.5) so u prolly wont tell much diff in idle
QDRHRSE
New Member
That cam has a lot of lift for that duration. Truthfully, the AFR 185 will flow almost the same with .500 lift and .534 . Other than the fairly high lift, that cam might as well be a broomstick for a 347. I realize that CHP builds a lot of engines but that doesn't sound like the greatest cam. I even question the LSA. It's quite short for a motor that will naturally make power down low. That souns like a cam for a smaller motor that needs more tq- sooner than later. Just me thinking.......
Grn92LX said:
It's not a guessing game, more of a learning game...Even if I had FTI do a custom cam, I'd still want to know the specs and I'd still want to understand what was going on and why my car performs the way it does...
BTW, I've have chatted with Mr. Curtis, he'll likely be doing my cam once my combo is complete, but the motor will possibly be going in with stock intake and exhaust...This cam will likely be temporary, but in the car while doing final mods...
As far as cams go, I understand the concepts but not the applications - that is - from reading, I know what lift, duration and lobe separation are, but I don't know how they relate to idle, power, and emissions...
It's kinda like knowing what passes, runs, and 1st downs are, but not having any idea how to put a drive together for a touchdown...Some guys are satisfied watching the hits and the great plays...I want to know what made the plays work...
Can anybody maybe refer me to some reading material? Maybe provide a link? I've searched quite a bit but haven't come up "cams for dummies" yet...
Here a a few of the useful sights I have found.
Still did not answer the questions I had the way I wanted them answered.
http://www.hotrod.com/techarticles/18218/index.html
http://www.hotrod.com/techarticles/113_9804_cam/index.html
http://www.hotrod.com/techarticles/113_0209_cam/index.html
http://www.hotrod.com/techarticles/49598/index.html
jason
Still did not answer the questions I had the way I wanted them answered.
http://www.hotrod.com/techarticles/18218/index.html
http://www.hotrod.com/techarticles/113_9804_cam/index.html
http://www.hotrod.com/techarticles/113_0209_cam/index.html
http://www.hotrod.com/techarticles/49598/index.html
jason
