Cam Tech

[hammerhead2]

I was training a new guy today at work and thought some of the info I was giving him may be good to post on here to help people understand cam specs a bit better. Cams tend to be a very misunderstood area of the engine and there is a lot of bad info out there, so maybe this will be helpful for some guys.

General Rules of Thumb when camming an engine.

1. As a head flow improves you can use less duration to maintain the same RPM range.
2. As rod length increases, torque and HP peaks will mover further up the RPM band.
3. As rod length increases cam duration can be decreased to achieve similar RPM.
4. Longer rods will slow piston speed down, which hurts velocity made by the piston. This necessitates the use of smaller cam duration to promote velocity.
5. Increasing stroke will tend to increase TQ. Keeping this in mind you can generally widen the lobe separation on the cam to widen the power band and a longer stroke engine will typically benefit from this.
6. Widening the lobe separation will broaden the torque curve though often reduce peak torque. (this applies mostly to durations above 230 @ .050)
7. Faster ramp rate lobes are useful in restricted applications or in RPM limited applications.
8. Slower ramp rate lobes are useful in higher RPM applications.
9. In EFI engines or applications with vacuum concerns less duration will allow for tighter lobe separation while larger duration will require wider lobe separations in these setups.
10. More aggressive ramp rates (faster) will often create more torque, HP, throttle response, and vacuum. Though they will create more valve train noise and require more spring pressure to control.
11. Less aggressive ramp rates (slower) will create less valve train noise and bleed off more cylinder pressure. They will require less spring pressure to control and be easier on parts life.


The way to measure ramp speed (faster vs slower lobes) is by simply subtracting the duration @ .050 form the advertised duration. This will give you the major intensity of the lobe design and lets you know how fast the lobe profile is off the seat. You can also check the lobe at .200 in comparison to the @ .050 and advertised durations to form a more total picture of the lobe design.

[hammerhead2]

What tightening and widening the lobe separation does.

Tight LSA (lobe seperation angle is the distance from intake to exhaust centerlines)
Moves torque to lower RPM
Increases Max torque
Narrows powerband
builds cylinder pressure
Overlap increases
Decreases vacuum
Increases cranking compression
More chopy idle
Decreases Piston to Valve clerance


Wide LSA
Raises toque through the RPM band
Reduces max torque
Broadens Power Band
Reduces cylinder pressure
Decreases cranking compression
Increases vacuum
Less choppy idle
Overlap decreases
increases Piston to Valve clearance

[ArkansasMystic]

Great info, thanks for posting!

[weeloGT]

Very helpful for someone doing some serious research before just picking a cam out. Should be a sticky

[03MistyV6]

great stuff man! i always tried figuring out what goes into cams and it makes sense for the most now. i wanted to do a cam fo my six just to have something different.

[hammerhead2]

Thanks guys. I will try to post a few more things as well as I think of them. Of course if anyone has any questions feel free to PM me. If I can't answer it I can get the answer for you.


Hey Misty if you do decide to do a camshaft we can set you up with something from Comp so you get your forum member discount. Also a customer of mine owns a shop called Super Six Motorsports and he specializes in 3.8 and 4.0 V6 ford engines. I am sure he would be happy to talk to you about it as well.

[03MistyV6]

i've window shopped on SSM and looked at all their stuff and was impressed by all the things they had for my sixer, had me drooling slightly ha. if i do just stick with the car and once i get some other parts on the car fixed, i was really thinking of doing a cam to wake it up. yeah i'll keep in touch and if the wallet permits, i'll send a line your way about the cams.

[hammerhead2]

Few other helpful hints on cam selection.

1. More cubic inch allows you to run more duration on the camshaft and still maintain streetability.
2. More cubic inch also requires more camshaft to maintain the same RPM range.
3. Smaller duration can normally be used in small cubic inch engines to still achieve a choppy idle.
4. A larger journal size will offer less flex at RPM
5. Flex at RPM can effectively shrink the cam specs
6. The split between the intake and exhaust durations is generally determined by intake vs exhaust flow characteristics of the cylinder head.
7. Always keep in mind head flow characteristics change once an intake and exhaust is added. So just because a cylinder head flows 75% on a bench that does not mean it flows that way on your engine.
8. If a blower or nitrous is added a litte more exhaust duration is benefical to help with cylinder scavaging.

[hammerhead2]

Also when discussing cubic inch regarding cam selection it is important to take note of the bore and stroke combo. As you can somtimes have a smaller cubic inch that would make more torque or need more camshaft for the same RPM range.

For example: If you have a 418 inch Windsor Stroker (4.030 bore with a 4.100 stroke) vs say a 440 inch Windsor Stroker (4.185 bore and 4.000). Then the 418 inch engine will actually need more duration to achieve the same RPM range than the 440. The reason for that is the smaller bore with a large stroke combo.

[broncobullitt]

What do you think your guys best grind is for a stock 2v with no ptv issues?

[hammerhead2]

Well the PTV issue is kind of questionable cause it depends on which pistons you ended up with from ford. If you have the low clearance pistons then the best one is our part number 102200. If you have the higher clearance pistons then you can use the 102600 cams. The 102600 cams make great power and have excelent street manners and good broad power band.

[hammerhead2]

Do you happen to know if your engine was from the Windsor plant or the Romeo plant

[gator72007]

I like Number 1
1. As a head flow improves you can use less duration to maintain the same RPM range.

This is also true to allow "large" heads to work well on a small cubic inch engine.

Say TFS190's on a 302, you would Use less duration than say
afr165's or gt40's on a 302, If you put large heads on a 302 and use a large duration cam, it will be gutless, Bigger the heads smaller you can go on cam, on a small engine, and you will also have a good idle.

[hammerhead2]

Thats exactly right. The only time you can really start using a large cam and large runner heads on a small engine like a 302 is if you have a lot of compression (12:1+) in the engine. Compression will put more torque and power back into the engine and will also pick up throttle response. You could also tighten the LSA of the cam to gain more bottom end. Of course those exceptions apply mnostly to a race engine as you are not likely to run that much compression or real tight LSA's on street motors.

[broncobullitt]

It's a romeo block

[gator72007]

Thats exactly right. The only time you can really start using a large cam and large runner heads on a small engine like a 302 is if you have a lot of compression (12:1+) in the engine. Compression will put more torque and power back into the engine and will also pick up throttle response. You could also tighten the LSA of the cam to gain more bottom end. Of course those exceptions apply mnostly to a race engine as you are not likely to run that much compression or real tight LSA's on street motors.

Where do you work?

[hammerhead2]

Sorry, I always assume everybody already knows. I work for Comp Cams in Memphis. I am a Tech Consultant for them and manage the E-Tech area, (webforums, e-mails, live chat).

[hammerhead2]

Also just so everybody that reads this is clear. I am a member of this site because I live in Arkansas and have and love mustangs. I am not here in any official form for the company but I would be happy to offer any help to anyone with questions about any of the Comp Performance Group Companys products.

[gator72007]

Also just so everybody that reads this is clear. I am a member of this site because I live in Arkansas and have and love mustangs. I am not here in any official form for the company but I would be happy to offer any help to anyone with questions about any of the Comp Performance Group Companys products.


Yea i didnt know you worked there, thats pretty cool, I had a cam quoted for my application a while back online, what do you think on what i was quoted? This is a play car, and i take it to centerville when i can.


90lx, stock short block, stock cam, TFS 170's OOTB, scorpion 1.72rr, Typhoon intake, 70mmTB, 73mm MAF, CAI, AOD, PI Stallion stall, silverfox valvebody, 4.10 gears, summit short headers, O/R x pipe 2.5, flowmasters dumped, ud pulleys, ac/smog delete, 99 cougar ele. fan. 4cyl springs, cheap tubular u/l rear ca's, jegs weld wheels 15x4 15x8, 265/50-15 street tires




heres the cam specs.



CCA-35-351-8
UPC 36584065999

Cam Style Hydraulic roller tappet
Basic Operating RPM Range 1,800-5,800
Intake Duration at 050 inch Lift 218
Exhaust Duration at 050 inch Lift 224
Duration at 050 inch Lift 218 int./224 exh.
Advertised Intake Duration 270
Advertised Exhaust Duration 276
Advertised Duration 270 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.512 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.512 in.
Valve Lift with Factory Rocker Arm Ratio 0.512 int./0.512 exh.
Lobe Separation (degrees) 114
Computer-Controlled Compatible Yes
Grind Number FW XE270HR-14
Valve Springs Required Yes
Quantity Sold individual

[hammerhead2]

Thats a great choice for you engine. That little cam will have a touch of lope to and great bottome end. It will easily out power the normal B or E cams from Ford and it is about as much as you can go with a stock piston with out needing to fly cut the pistons. Those heads would benefit from more lift but then you would have to fly cut for it to clear. You should be quite happy with that camshafts performacne vs your stock cam.