Will someone give a semi-technical description of camshafts? How does a different camshaft improve power? Can you explain the numbering system? What is involved in replacing one? Does the engine come out? What are the associated springs and are they necessary? How does it affect both sound and driveability?

Thanks!

Edit: For those interested, I found this website to be interesting and informative, with great diagrams: http://auto.howstuffworks.com/camshaft.htm

 

Basically the cam lifts your intake and exhaust valves to let air and fuel in, and exhaust gases out. Stock cams have a very short duration and lift. and a high lsa to keep the idle smooth. A "bigger" cam allows more air and fuel and gets more exhaust gases out. First numbers: Duration, in other words, how long the valve stays open, which is not the same as lift; lift is how far the valve is pushed open. LSA, "Lobe separation" is the degrees of time from which the intake valve closes and the exhaust opens. It seems very confusing at first, but when look at how a cam works it makes perfect sense. A mild cam would have #s like 220/220 duration, 560 lift, and 115 lsa. A nasty cam would be 236/240, 600 lift. and 112 duration. for example. A cam swap is quite a project, for a back yard mechanic. Remove the radiator, brackets, water pump, timing chain, rockers, push rods, and lifters. If you are not an avid mechanic, I would not try it, pay a "good" speed shop.

 

Duration is key to Power!

 

So what's the downside? Rough idle? Poor mileage? Engine life / reliability? Also, how does it affect the sound?

I'm sure a new cam would destroy the warranty, right?

 

Engines are pumps, it is all about the volume of air you can most efficiently get in and out of the pump.

Lift and duration dictate how high and how long the valve is lifted off of the seat, lobe separation times the correspodence between intake events and exhaust events. Most cam specs are posted
xxx\xxx (duration in degrees) .xxx\.xxx (Lift in inches) xxxLSA (spacing bewtween intake events and exhayst events in degrees).

Downsides are increased emissions, higher RPM peak HP numbers, rougher idle (mostly caused by lower # Lobe separation, but also total duration), could decrease mileage. For the most part with a 6500 RPM redline you can go with a significantly larger camshaft than stock and avoid most of the downsides. For example a 224/224 .56x/.56x on 114 would be a great all around camshft that would most likely pass emissions, idle well (not as good as stock), get good mileage....As far as reliability goes camshafts will not hurt except for the fact that they will put more strain on the valvetrain, and you will have to maintain this aspect much more than stock (replace valvesprings mostly).

And yes, engine and drivetrain warrenty would most likely be out the window unless you have a very cool dealer.

 

It's always a trade off. The trick is to match all of the mods A small change in cams can make a big difference in performance. That can be bad as well as good. If you install a hotter cam, you have to induce more air/fuel and be able to get rid of it via better exhaust. People have actually installed cams and LOST performance. This has addressed since the 50's.

 

If you are woried about driveablity and warranty a good option to go with is a stealth cam, MTI has a good one that posts very good #s, up to 30hp, and you can't tell that it is there when it idles.

 

I am worried about warranty, but not driveability. I don't want it to drive like a racecar, but a little more blub-blub-blub-blub sound would be cool.

 

Yeah its a tough call, I look at it this way, this is one of the best engines made and it is highly unlikely that you will have any problems going with a moderate cam, if you get up over say a 570 lift, I would upgrade your springs. Good luck.

 

Here's another thing to think about:

That cam swap might, if you choose well, yield 30
rwhp at 6000 rpm with no real loss in power down low.

That's less than a 10% power increase, almost all of it
coming over 4000 rpm so you won't really feel it unless
you are revving your engine pretty high. It will drop
your et and add a couple mph to your trap speed.

On the other hand, if you were to do a gear swap, and
exchange the 3.42 rear gear set for a 3.90 rear gear
set, you'll feel a lot more "oomph" in every gear, 15%
more rear wheel torque, to be precise. The thrust
when you plant your right foot will feel lots more
dramatic than with a cam change. The car won't
actually be much faster at all in the 1/4 mile though
because while it pulls a lot harder in each gear, you
are in each gear for 15% less mph than before. Mostly
it'll be a draw in a 1/4 mile race.

So there's the paradox. One mod will definitely reduce
your et and raise your trap speed but won't be that
dramatically felt while driving. The other mod will make
your car feel much stronger but it won't actually drop
your et or raise your trap by much.

The cam change has a lot of implications on things
like warranty, passing emissions, reliability, etc, etc.

The gear set change will just drop your highway mileage by a mpg or two.

Interesting, isn't it?

Pat

 

Or you could do both and really feel the difference!

 

If you are worried about warranty, leave it stock or put some mufflers on it so it at least sounds good.

The key is a combination of mods to get the desired results. The right head /cam combo will get you all the torque and hp at different rpm levels and still be streetable. Cam only works OK but when you add the heads it makes the cam perform at a whole new level. When you add headers the cam/heads mod goes to the next level and finally tuning brings it all together.

My head/cam, headers, tuning package is very streetable. The difference is that it nows runs with the big dogs.

my 2 cents

 

Thanks for the advise and recommendations. Something to consider. I think I might let some time pass, then consider doing the whole shebang at once - head / cam / headers / exhaust / tuning. Seems smartest, but I don't want to drop the cash right now.

 

YOu might look into the Thunder racing old man cam or the MTI stealth cams...I would doubt that the dealer could tell you have a cam in there if you leave the stock rear section exhaust. Of course if you broke something in the motor they would more than likely be able to tell you changed the valvesprings...But if I changed the cam and broke a valvespring I would fess up to it and pay for the damage myself..Just a thought.