Howdy motoring gurus.

I'd like to learn more about cams and how to read their specs and know how they will perform in an engine - namely mine.
My engine will most likely be mildly modified in the long run so bearing that in mind I'd be looking for a cam to improve my low and mid range power. Now, how do I choose which cam is appropriate? Will it depend on what mods the engine currently has or on what mods I intend to have?
While I believe I have a basic grasp of the cam and its function, I'd rather have it properly explained by people who understand them far better than I do. The more education, the better!

I'm no expert but heres what I look at:

Lift - Obviously the more lift the more air can flow past the valve. Most production heads flow well to about .500" lift so you will see most aftermarket cams go to just above that. Lift is limiited mainly due to mechanical issues. Higher lift generally means more power across the rev range without effecting the overall engine dynamics (ie still retains good idle and low down power).

Duration - Larger duration increases power/torque but also moves the power band higher, menaing low down torque suffers but high end power increases. It also dereases idle quality. (On the V8's under 220 degrees @ 0.050" will give reasonable idle quality)

Lobe Seperation (LSA) - High LSA means good idle and good high end power. Lower LSA means decreased idle quality, better midrange but will limit high end power to some degree. (110LSA gives a passable idle probably more suited to manuals, 112-114 decent idle with auto or manual)

Other than that, look at the power band that is advertised. That will give you a good indication where decent torque will be available, stock cams are aroudn 1500-5000rpm. IMO you want to keep the minimum value at around 1500-2200max as that will give you the best streetability and the top figure usually around 5500rpm.

So lower duration cams will give me power in the lower RPM range and a larger duration cam will operate at higher RPM, but I will lose bottom end power to gain top end power as the duration is increased?



Other questions;

1. If I were to already have installed roller rockers to my engine then cam selection would have to take that into account wouldn't it?

2. Can you explain solid lifters, roller lifters, hydraulic lifters etc?

Solid lifters are just that..
Std type have oil inside to adjust any gap or clearance from oil supply in engine...

Roller cams and lifters have quick opening and clossing ramps that a flat tappet cannot generally do..The roller lifter has a roller bearing where it contacts with cam...The down side to this is the roller lifter is heavier and limits rpm to 6500 plus the lifters start pumping up at that rpm...But most street engine don't rev that high anyway....Roller engines generally have higher spring rates than flat tappet..Or should!!!

A wider lob center gives you wider power band but not as peaky especially mid range.......Short stroke motors like 5.0 respond well to 110* cams..It enhances the revability of the engine...

The only reason roller rockers have anything to consider with cam selection is "rocker ratio"...Going from 1.6 to 1.72 on average raises valve lift .030...Unless lift is extream a 1.72 rocker can can be used on cam advertised with 1.6 ratio...Valve to piston clearance must be checked by using model clay and turning engine over then measureing clay thickness...Good double valve springs help keep harmonics etc in check also as both springs opperate better in differant rpm / harmonics range....

So what would be the specs on the stock Ford cam in the HO windsor?

Stock cam is .444" lift, 204@50th and LSA of 116

This is quite a good thread! May make it sticky if we can get some more tech talk in here.

My question is what exactly is the 0.050" in reference to for duration?

Also what is there to take into consideration for in/exh open/close timings. What general effects do we see with variations of the valve timings.

I think duration is the amount of time measured in degrees of crankshaft rotation and the 0.050" might be referenced against lifter rise.

I understand that duration figures quoted "@ 50th of an inch" is the actual time the valve is at 0.050" lift off of the valve seat...

i.e. quote @ 0.010" and the duration figure would be higher, as it is being measured at a lower lift from the valve seat....

So, my understanding is that the higher the overlap on a cam - the poorer the idle quality and the better it is in high RPM... is overlap purely dictated by duration? Or is it a range of specs that effect this?

I've noticed with my engine that when the tacho reaches about 2700 RPM, it really starts to go harder and I get a nice shove in tha back. Would this be my stock cam entering it's power band?

Also, what are the advantages and disadvantages of hydraulic camshafts vs. haydraulic roller camshafts? Is the HO windsor a roller block or a non-roller block?

Hydro no need to adjust..
Mech have to adjust and can be noisy...

EFI windsors are roller...Or U.S from 85...

@ .050 is where a cam is measured to be more acurate ....
Advertised is what it is straight up...
Usuall and it depends on grind but 220/ 220 @50 cam is roughly the same as 280 / 280 advertised...As in E303 SVO cam...

Also on the subject of cams. What is the largest cam you can run with a GRA setup on a 302? Many people have said that GRA setups need a vaccum of around 15" of H2O. That would mean that the cam would be very close to stock. I'm sure that you can go wilder than that.

My cam is 236 /224 550 lift 114 lob centre and have 18 Lb vacuum...