TraviZ

iTrader: (2)

example:

Adv. Duration: 270º/276º
Gross Lift: .452''/.465''


can someone please explain how these numbers work and what their meaning is? thanks!

87350IROC

iTrader: (2)

First of all, look at the duration specs @ .050". Duration is how long a valve stayes open, lift is far the valve opens.
JP

TraviZ

iTrader: (2)

then what do the two numbers stand for?

would the valve open 270º @ .452"


if so, whats the 276 & .465 mean?

87350IROC

iTrader: (2)

270 & .452 are for intake valves
276 & .465 are for exhaust valves
Like i said you need duration @ .050" which should be given, it is a much better indicator. The life values are maximum lift. As the cam turns and as soon lift starts duration also starts Duration is starts at 0 lift, climbs to max lift, then back to 0 lift then duration ends.

TraviZ

iTrader: (2)

oh ya duh


now can you explain what you mean by "duration specs @ .050". "

ede

cam grinders have sort of settled o n.050 as where they measure lift at, but not all of them do so pay attention when you look at cam specs. as for 50 state legal i'd worry more about the state i lived in. look at the catalogs it'll say what's legal and where.

TraviZ

iTrader: (2)

i found this one

http://www.jegs.com/cgi-bin/ncommerc...57&prmenbr=361

how can i tell if its measured at .050" or not?

it is

Adv. Duration: 272º/284º
Gross Lift: .454''/.480''

five7kid

iTrader: (14)

"Adv. duration" is "advertised" duration, the total amount of crankshaft degrees that a lobe is lifting the valve off its seat. Since the first .050" inch or so of that lift doesn't do much performance-wise, a better comparison of cams is to measure the duration ignoring the first and last .050" of lift, which will be 216/228 for that cam.

The "gross lift" numbers are how much the valve is opened off the seat (total). It assumes 1.5:1 ratio rockers for small block Chevy.

The numbers before the "/" are the values for the intake valves, and after the "/" are for the exhaust.

That cam says "emissions legal", which means it is a legal replacement for the application(s) listed.

I just happen to have that cam. Love the way it runs, and easily passed emissions testing last month.

five7kid

iTrader: (14)

I see you have an '89 305 TBI. Two reasons that cam wouldn't be a good one for you: 1) You've got roller lifters, it's flat-tappet. Get the roller lifter version. 2) TBI heads are pretty much dead dogs when it comes to performance improvements. You could put a bigger cam in it, but they're so flow-restricted, the improvement would be minimal.

TraviZ

iTrader: (2)

im not gonna put it in my 350, im doing resaerch for my 350 I am building as a 2004 project.

i've pretty much narrowed it down to this:

350 GM small block
Bore: 4.030"
(.030" over)
Item # xxx-xxx 1 x $50.00

** EdelBrock Products Heads
Performer
3/8" rocker stud
5/6" pushrod diam.
64cc straight plugs
(requires heat treated pushrods .100" longer)
int 170cc valve size 2.02"
exh 60cc valve size 1.60"
Item # 350-60909 2 x $978.98

** Proform Roller Rockers
STeel Tip
1.5 Ratio 3/8" stud
Item # 270-11806-16 1 x $179.99

* Eagle Crankshaft
Cast Steel
3.480" stroke
2 peice rear seal
Item # 356-103503480 1 x $192.99

* Eagle Rods
SIR
5.7" bushed
Item # 356-SIR5700BBLW 1 x $319.99

* Claimer Pistons
Flat Top hypereutectic
+.030"
64cc - 10.4:1
Item # 648-H3418.030 8 x $159.92

* Crane Cams Camshaft
350 5-spd. w/3.73-up.
Adv. Duration: 272º/284º
Gross Lift: .454"/.480"
Item # 270-114142 1 x $154.99

* Crane Cams Hydraulic Lifters
55-91 SB
Item # 270-99277-16 1 x $89.99

* Crane Cams Pushrods
Chrome moly 5/16"
7.900", +.100"
(Heat Treated)
Item # 270-95636-16 1 x $143.99

Edelbrock Intake Manifold
EGR
TBI
87+ heads
Item # 350-3704 1 x $219.99


that exluding gaskets/bearings/oil stuff.

F-BIRD'88

50 state legal cams are cams that have been tested and verified by the manufacturer to the satisfaction of the CARB board and EPA to not adversly affect emissions when properly installed as a replacement for a stock cam.

Many ( but not all) of these cams are just repackaged common cam grinds with new part numbers and a higher price.

the EPA or CARB will never know what cam you installed unless you tell them though.
There are many performance cams that are suitable for a smog motor and will pass a smog test just fine, that are not "50 state certified". The difference is the testing and verification and documentation. And the $price$
Most of the mild(er) hydraulics with 112 or wider LSA's
will do what you want. Keep the .050" duration less than 224 @.050".

Something between 203 and 216 @.050 is good for mild/moderate smog friendly buildups.

Some of the cams are specificly designed to be EFI computer friendly. (special and specific cam lobe ramps and overlap are built into the cam grind to maintain the engine's idle manifold vacuum so the computer does not get all confused. These are specificly designed to be more fool proof for the average installer.

Confuzed1

iTrader: (4)

I guess that could be true. Depending on what you go with. I know I run a Crane Compu-cam 2040 with no problems. After I rebuilt the engine and changed the CAT, I've passed 3 times in a row with no problems.

I think 5-7 kid runs the 2050 version.....and does well AFAIK.. neither cost any more than any other cam though.

Yep...I agree 100%....I know this will age me, but I used to run a Crower "Baja Bomber" cam in my '72 Charger and had no probs either....I think if you can maintain a decent vacuum at idle and keep it tuned properly, it'll pass.