Teach me about cam shafts!

I have a general understanding about pretty much everything within an engine except the cam shaft. Now I'm not talking about how the cam shaft pushes the push rod (or directly on the valve springs) to activate the valves. What I have never understood is 110lsa vs 112lsa and all of the numbers for lift etc etc...

I know its a little specific but I was curious about What it all means and cant really seem to find a good resource.

 

Also I couldn't figure out what section to put this in so move as you see fit.

Back from my drag racing days...LSA is lobe separation angle. Which usually will give you an indication of overlap.

 

You do NOT want any overlap on blower/turbo motors since you would get raw fuel blowing thru the chamber and into the exhaust.

 

On naturally aspirated engines, a little bit of overlap helps since the exhuast flow will help 'pull' in the intake charge.

 

Lift used to be measued with a 1.6 rocker. So if you used a 1.73 rocker, you could get more lift (how far the valve will open into the chamber)

 

Duration is given at .050" of lift. This will tell you how long (in degrees) the valves will be open. You can have different durations for exhaust and intake valves if you wanted.

 

Then alot of it comes down to 'where' you put the cam in. Machining differences in blocks/parts could change the alignment of the cam vs the crank - i.e. when the crank is at TDC on #1, it may be a few degrees off on the cam TDC. This is when you would want to 'degree' a cam. You could also move the cam back and forth a few degrees to give more more low/top end.

 

I'm sure alot has changed, but those are some of the basics...

 

Another thigh to add about lsa. The lower the number the rougher it runs. My 98 Formula had a factory 116 I had a 112 in there so it ran much rougher.

thanks mike that was put so simply that it actually made sense in my little brain!

 

So if I understand it correctly the lower the LSA the more "cam lope" you will have?

thanks mike that was put so simply that it actually made sense in my little brain!

 

So if I understand it correctly the lower the LSA the more "cam lope" you will have?

Yep. Buy I don't know if the lower number means more or less overlap. I would think more but with the lower number I'm not sure. I didn't know half the stuff mike posted, so I'm far from knowledgeable on this topic.

So if I understand it correctly the lower the LSA the more "cam lope" you will have?

 

I believe so...Imagine if at 114 lsa you have no overlap...At 112 you have 2 deg overlap...At 100 you have 14 deg overlap...

 

Just for fun...At ZERO deg LSA - you have an intake and exhaust valve both fully open at the same time.

 

It seems the more overlap the more 'radical' the cam....When you hear a 'lumpy' cam, what you are actually hearing is the engine sort of misfiring because of overlap...Usually not good for low end power, but as the RPM increases, so will the efficiency of the cam, and make more power than one with less overlap (at least on a naturally aspirated engine.)

 

I am far from a cam expert (cams are literally a science), and it's been a long time since I messed with engines and racing, so don't take my info as gospel; Just pulled a few bits from the dusty parts of my brain.

 

http://www.popularhotrodding.com/enginemas...pecs/index.html

Back from my drag racing days...LSA is lobe separation angle. Which usually will give you an indication of overlap.

 

You do NOT want any overlap on blower/turbo motors since you would get raw fuel blowing thru the chamber and into the exhaust.

 

On naturally aspirated engines, a little bit of overlap helps since the exhuast flow will help 'pull' in the intake charge.

 

Lift used to be measued with a 1.6 rocker. So if you used a 1.73 rocker, you could get more lift (how far the valve will open into the chamber)

 

Duration is given at .050" of lift. This will tell you how long (in degrees) the valves will be open. You can have different durations for exhaust and intake valves if you wanted.

 

Then alot of it comes down to 'where' you put the cam in. Machining differences in blocks/parts could change the alignment of the cam vs the crank - i.e. when the crank is at TDC on #1, it may be a few degrees off on the cam TDC. This is when you would want to 'degree' a cam. You could also move the cam back and forth a few degrees to give more more low/top end.

 

I'm sure alot has changed, but those are some of the basics...

 

Thanks for sharing. Just educated myself.

http://www.popularhotrodding.com/enginemas...pecs/index.html

That dumbs it down pretty well and yet it has a But load of info thanks!!