Ok. I'm trying to learn all I can bout these engines so I'll understand what you guys are talking about. Now I got all this stuff memorized...but I don't UNDERSTAND it...
I'm reading Lingenfelter's book on SBC engines.
I've drawn my own diagrams (the circle with intake and exhaust valves overlapping on both ends is stupid! exhaust-->intake overlaps, intake-->exhaust does not).
So I need help understanding airflow dynamics.
Lingenfelter talks about long, small xsec intake runners helping with low end torque suffering at high end hp and vice versa...that I think I understand...its a velocity vs mass issue right?
What I don't understand is exactly how advancing/retarding the cam works, especially when trying to also understand lobe separation angle performance...
According to the book advance-->torque; retard-->power; tighten lobe separation (yes, I know I'm oversimplifying...ignoring duration, displacement, etc)-->torque at expense of idle, and high end hp...
Surely it isn't as simple as both advance and tighten opening intake a little sooner?...the difference in advance and tightening (in my models) is later opening of exhaust valve with tightening...what effect does this have? (seems to make the torque/hp change more pronounced)
Thanks in advance for all your help...I'm trying to get it...but if I don't understand, I'll never remember!

 

i have a had time explaining things so go to Comp Cams web site and they
have a ton of info. don't :lol: take note's as you read for reference and
write down questions to look-up or find other places :flag self ed. i live by it
:party:

 

Keep reading as it takes a while to all fit together. Try the David Vizard books too. But you don’t need to redesign a camshaft to make a good selection. Plenty of help on the manufactures website and try calling their tech assist number too. And BTW there’s too much to write about here when there’s plenty of good books available. :seeya

 

I'm not an expert, but I can try to explain it a little.

The intake opens before the exhaust closes so that the momentum of the exhaust flowing out of the chamber helps to draw in the next air/fuel charge.
The intake does not overlap the exhaust be cause you need to have the compression stroke between them...


Long intake runners will improve low end grunt (Torque) because of the velocity that is created, and the air/fuel charge will also not stall (stop) because of the added volume of the runner.
The short runners are better for horsepower at a higher RPM because there is less turbulence and more airflow, sort of like water flowing down a long channel. If this makes sense. then read on.

Now think of the long runners at high RPM and the short runners at low RPM and apply the opposite effects to them and you will see why they work the way they do. Hopefully this has you throughly confused now....

And since it''s late at night, and my brain is shutting down as noted in the last explanation. I don't think you would want me to try to tackle the last question you have.....

And besides, I'm sort of lost on what you were trying to ask there... :lol:


We now return you to the regularly scheduled program. :thumbs:

 

i don't type real well ether :crazy: the size and length affect the "reversion"
also. that's when air & fuel "mixture" run into the valve when it close's and
bunce's back the opp. direction. it starts a pulse wave . back up the port,into
the intake man. then intake opens and the low pressure in the cyl. is filled
with mixture again if the wave is tuned(timed) right it's headed at the valve
when it opens helping fill the cyl. (ramming effect) is this making any sence
i'm far from a teacher, :confused:

 

another good book is Smokey's it's old school and straight forward :thumbs:

 

A good site is http://www.n2performance.com

:cheers:

 

Thanks vetdrm, that is a great site...am printing the lectures as I write...

I've found the answer to my last question and will post it here for future reference, even though those of you who responded surely know the answer...
I've got some great diagrams, but have no place to host them to post here...

I read that intake valve closing has the greatest effect on torque/hp relationship...exhaust opening has a bit less...and exhaust closing/intake opening fairly little.
It is this fact that advancing the cam will increase low end torque (though exhaust opening is earlier, favoring high rpm hp...intake closing overrules, closing earlier and giving more low end torque)...and the same reasoning can be extrapolated to retarding...likewise by decreasing the lobe separation angle, you close intake closer to BDC (low end grunt) AND open the exhaust closer to BDC (low end grunt) and that's why we see a more pronounced difference than with advancing...
make sense?
Again, thanks for all you guys help!

 

yep! loks like a good site :thumbs: i'm outta' ink :cry :banghead:

 

are ya' startin to pick it up or getting more confused :skep:

 

lol
I had it :cool:

now I got it :party:

:hurray: :hurray:

 

got ink now i hope i got enough paper :lolg: start printing , eat somr supper
and do alot of reading looked good when i scaned the screen :thumbs: :lurk:

 

Check out this web site. Its animated and moves in slow motion to make it eaiser to understand. Click on engines. I think you will like it. Good luck. http://auto.howstuffworks.com/cooling-system11.htmto