ended up with a 300hp/327 factory cam in a deal I made recently. What would this do for a 305 with performer intake, 600cfm edelbrock carb, headers with 1 5/8 tubes. Should be more radical in the smaller displacement, but I wonder how much? Appreciate your input.

Dead smooth idle. Pulls from 1000 up to about 4200 strong. I run it with a 625 Carter and 1 1/2" headers. With a 200R4, 3.73 gears, and a 26" tire I get 21mpg. Weight 3000lb. This is the same cam Chevy used in a bunch of different motors. 307, 327, 350, and 400. .390/.410 , duration at .050 is like 194/204. About one step over an 80's 305 grind. My motor is an 84, had something like 187 duration stock. Dan

I'm not well versed on cam specs or really understand what all the numbers with this cam mean, so I will post them.

050 dur.....adv dur.....sae dur.....cam lift
int exh.....int exh.....int exh.....int exh
204 214.....270 280.....278 288.....280 295

valve lift
int: 420 exh: 443

lobe center overlap
int exh
107 117 51 cmc number 151850

I would appreciate an intrpretation of these numbers. This a federal mogul cam.
thanks

[ December 18, 2002: Message edited by: beetle9 ]

[ December 18, 2002: Message edited by: beetle9 ]</p>

The cam specs you listed are nt the 300hp/327 they are like the summit brand # k1102.This is nice cam for 305 torquey with a little more mid range pep.This cam or the step above it are about perfect for a mild 305.Smooth idle.At best might sound like a pickup truck(boarder line lope).

I can give you a run down on some of the cam specs. The cam you have is one step bigger than a 300hp 327. Each step having about 10* more duration. Duration is how long the valve is open in degrees of crankshaft rotation. Different grinders measure from different points. SAE is normally measured at .001" lift. Advertised depends on the company. .050" lift numbers came about so the cams could be compared from one grinder to the next. The duration at .050" is what you look at when figuring the true size of a cam. Advertised numbers vary by a good bit.

Lift: Lobe lift is how far the lifter rises. Valve lift is how far the valve opens and is dependent on the rocker arm ratio. Your figures show the use of stock 1.5-1 rockers. .280" X 1.5 = .420" If a 1.6 rocker was used, you would have .448" valve lift.

Lobe centers: If you mark a degree wheel when the intake valve starts to open, then mark it again when it closes, you will have rotated the crank 278*. The intake valve opens before top dead center, and closes after bottom dead center. Half way between these opening and closing points is the lobe center. Your specs say this should be at 107*. You figure the exhaust lobe the same way. The cam turns at half the speed of the crank. The crank would be 1 full turn and 10* past your intake center line.

Lobe displacement angle or lobe seperation angle is a spec many give. It is the angle between the lobe centers. In your case 107 + 117 = 224 / 2 = 112*. Comp gronds on a 110* center, Crane a 112*. Most factory cams had something in the 114* range. Race cams 106 or 108*. Again, playing on the overlap. Wide angles have a better idle where narrow makes more peak power.

Intake valve closing point: The sooner the valve closes, the more cylinder pressure you will make. Holding it open longer will allow the cylinders to be more fully filled. The later a closing takes place, the higher the rpm you would have to turn to take advantage of the ram effect of the intake charge.

Overlap: The exhaust stroke is followed by the intake stroke. The intake valve opens before top center and the exhaust valve after. The period that the two are open at the same time is the overlap. A lot of over lap hurts gas mileage but the exhaust pulse leaving will help start the air/fuel moving in the intake runner. The more overlap you have, the higher the rpm has to be to take advantage of the exhaust pulse.

If you have followed threw all this and understand any of it, give yourself a pat on the back. Camshafts are very complicated and this is only a taste of what there is to know about them.

Rule of thumb:
All specs listed in the catalog are for a 350(Chevy small block cams).
You can expect to move your power band 500rpm for every 10* difference in .050" duration. That means you will loose 500 off the bottom to gain 500 on top.
If you change the engine size by 50 cubes you get the same 500 rpm change. If a 400 has the same cam as a 350, it will peak power at 500rpm less than the 350. A 305, 500 higher.
LDA or LSA angles should be wide for the street and narrow for the track. A wide angle makes the power band wider at a cost of peak power. A narrow angle will make more peak power in a tighter power band. At the tack you can gear the car to keep the motor in it's narrow power band.
230* @ .050" is about the cross over point where you are making the most power "Up Stairs". 220* in a 305. "Street" and "Torque" are not words used with cams over 230*.
If you use a cam that is too big for the heads, compression, intake, carb and exhaust you are loosing a portion of your power band. If a cam with a power band of 2500-5500 is used with heads that only flow to 5000 you have lost 500 rpms of usable power in the bottom end that you can't get back in the top. The motor would run stronger with a size smaller cam....
A bigger cam will give you less cranking compression. The intake valve closes later meaning it doesn't trap as much air until the rpms are up. The bigger the cam, the higher your compression needs to be. Shoot for 160-180 psi cranking compression for the street.

These rules of thumb are just that. A 302 and a 305 will act different with the same cam. Bore, stroke, rod ratio, and head flow plays a part as well.

The cam you have will be a good one to use in you motor. I don't like to go over 210-212* @ .050" in a stock headed 305. Any more is a waste. Dan

Ohio Dan, excellent reply and description of the cam and how it works. Maybe that post should be in the knowledge base.
Devon

thanks Ohio Dan and others responding to my question. I will install this baby in my 305 and see how it does.