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914World.com _ 914World Garage _ Guess my cam!

Posted by: toecutter Apr 15 2005, 11:54 AM

Is there any way to figure out what kind of cam the PO installed without splitting the case? The reason I ask is since I need to clean/rebuild the carbs I want to make sure they are set up for the cam. Is there a trick or am I SOL? FYI this is a 2.0 with what I am told are 1.7 heads. The carbs are Weber 40 IDF's (not 44's). I have a Compufire and SS heat exchangers. It was running like a spotted ape until recently because of grunge getting into the carbs. The fuel filters looked like they had a little poop in them. I digress. I believe the PO bought the webers and put them on right out of the box. Just looking for some advice (as always).

Posted by: skline Apr 15 2005, 11:56 AM

Nope, its a tear down in order to determine your cam.

Posted by: MattR Apr 15 2005, 12:04 PM

Cant you figure out valve lift without a teardown? Duration would be tough, but if you know lift maybe you could narrow it down?

Posted by: Dr. Roger Apr 15 2005, 12:17 PM

Is your crank puley degreed and can you see it?
If so remove one valve cover. Then pick one cylinders intake exhaust valves.
Hand crank slowly until you note the intake to just begin to open. Note how many degrees before top dead center it is (TDC).
Continue turning (did I mention it must turn in correct direction) until it just closes. Note how many degrees after TDC. Do same for the exhaust. How many degrees were the intake and exhaust valves open for?

Also note, this will not be accurate due to valve lash but can get you close...

Posted by: Aaron Cox Apr 15 2005, 12:39 PM

i agree....
you can see (within a relatively close range) what your lift is by measuring lift at the rocker. how much did the pushrod move?

like the above mentioned....
if you had a degreed pulley you could check your duration....

match the numbers up to web/elgin/eagle/isky cam specs and you can take an eductaed guess.....

Posted by: Mueller Apr 15 2005, 12:42 PM

get a dial indicator and you can get a good idea on the lift of cam....

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Posted by: bondo Apr 15 2005, 12:55 PM

Have it dyno tuned.. if you make more power than should be possible with a stock cam, it must be something else

Posted by: ArtechnikA Apr 15 2005, 01:55 PM

QUOTE (Mueller @ Apr 15 2005, 01:42 PM)
get a dial indicator and you can get a good idea on the lift of cam....

although .. measuring lift at the valve, you have to factor out the rocker arm ratio.
you need to measure lift at the lifter (or pushrod) to see the same numbers the cam people use...

Posted by: Aaron Cox Apr 15 2005, 02:07 PM

QUOTE (ArtechnikA @ Apr 15 2005, 12:55 PM)

QUOTE (Mueller @ Apr 15 2005, 01:42 PM)
get a dial indicator and you can get a good idea on the lift of cam....

although .. measuring lift at the valve, you have to factor out the rocker arm ratio.
you need to measure lift at the lifter (or pushrod) to see the same numbers the cam people use...

or divide out your rocker ratio

yeah... just dial indicate your pushrod....

Posted by: TimT Apr 15 2005, 05:20 PM

you can find out lift and duration with a degree wheel and a dial indicator.

take all play out of the valvletrain ie zero lash, then measure at lift at the pushrod. You can plot reading etc max lift of X in at X degree of crank rotation, then repeat with the other lobe.

you can even plot the lobe profile. to see how rapidly the valve is opening..