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Stock cam 1.3 rocker?

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Vincent

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Has anyone tried a 1.3 hemi rocker with stock cam and 36 lbs. Springs. I'm trying for torque,duration on stock cam is 230 and springs and 1.3 rockers gives me lift and rpms
 
why in the world would you use 36lb springs with a stock cam? Those springs would wipe the lobes off the cam. You wont find more duration with a stock cam without welding and altering the lobes, but you can play with the torque curve by twisting the cam to alter the lobe separation
 
Vincent said:
Has anyone tried a 1.3 hemi rocker with stock cam and 36 lbs. Springs. I'm trying for torque,duration on stock cam is 230 and springs and 1.3 rockers gives me lift and rpms
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"Camshaft theory", is a very complicated thing, you only have to look at the number of cams available to get an idea of how complicated it is.

Changes in duration, lift rates, total lift, overlap, (and other things) all have effects on an engine's performance. Combining all these aspects, to increase the power output of any given engine, is an art (theory), not a science.

Be aware that engines "only" make torque! You can graph the torque curve. You can calculate the horsepower and graph that curve. Be aware that any change in the intake/exhaust event will effect the torque curve. This "could" have consequences for your clutch slip and gear ratio.
 
Zach running bigger ratio rockers will increase duration though it is slight it changes the opening and closining numbers.ratio rockers open quicker and close later..
 
W5R said:
why in the world would you use 36lb springs with a stock cam? Those springs would wipe the lobes off the cam. You wont find more duration with a stock cam without welding and altering the lobes, but you can play with the torque curve by twisting the cam to alter the lobe separation
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When you say twisting the cam to alter the lobe separation, I presume that you weld the cam and regrind it, not really twisting the cam between the lobes.
 
They used to physically twist cams, I cannot imagine anyone doing that now with the variety of cams out there. You will not come up with something the cam manufacturers haven't already seen or done.
 
TiBeu said:
When you say twisting the cam to alter the lobe separation, I presume that you weld the cam and regrind it, not really twisting the cam between the lobes.
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No i mean literally putting a cam in a vice and twisting the lobes....if you have no experience doing this i would not mess with trying it, your more likely to screw up your cam....better off to just buy a better cam instead unless you have alot of stock cams laying around to play with
 
sportmod45 said:
Zach running bigger ratio rockers will increase duration though it is slight it changes the opening and closining numbers.ratio rockers open quicker and close later..
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Not being an expert on this stuff, I'm having trouble seeing what you're saying. If both rockers have the same clearance on the valve stem, and they both start moving at exactly the same time, how could that change the duration. I can see it changing the left, and I can see the acceleration of the valve increasing, but not the duration. Yes it lifts it faster, and higher, and closes it faster, but that doesn't change the duration.
 
I don't think it will directly affect the duration as a whole, but you'll have more lift at .050" than you would with stock rockers. While the valve may not be open any longer, it will be open more the entire time that it's open.

(Edit) if you want to split hairs, the 1.3 will take up any existing valve lash with less movement technically increasing duration if measured at the valve. Unless you run zero lash....
 
Put a degree wheel on and check it.if your valve reaches 050" at say 54*btdc and reaches 050" again at 90*abdead center.then put on higher ratio rockers and watch it open soon and close later..if that is not more duration then tell what it is...
 
Al you stated you could see more exceleration of the valve.then you should understand it will reach a determined lift quicker which effects the time(duration)that its open.
 
It depends how you determine duration. The duration from 0" open to fully closed does not change. If you measure from a determined distance that the valve is opened the duration will have changed in comparison to lift. Duration is determined at the crankshaft not the camshaft. It really is simply how you wish to define the events.
 
I use to really be into cams. Before karts, I was into drag racing. (Full race cams, 320° duration, .550 lift, roller lifters and roller rockers) It was my understanding that the duration of a cam was measured from opening to closing. Using 1.3 rockers does not change the opening and closing point of the valve, the cam does that. 1.3 rockers open the valves faster and raises them higher, I can't see where they change the duration.
 
There not measured 0 to 0...Al 320* is an advertised duration...look for actual duration numbers when it comes to v8s..kart43 your right duration doesn't change from 0in.to 0in...that is advertised duration..if you look in a kegs catalog you will see some manufacturers use an advertised duration number and some use actual duration which is measured from .050 to .050..some adds have it listed as " adv.dur.286*)or whatever there number is.kart cams are detailed at .050 to .050. So when you go to a bigger ratio the valve reaches this .050 lift sooner in the cycle though its not much maybe 1 to 3 degrees or so and then takes slightly longer for it to return to .050..it is slight but it increases actual not advertised duration...I had trouble myself grasping this until I checked it with a degree wheel myself..just go out in your shop and give it a try.
 
Al just look at a jegs catalog or do a search..some cam manufacturers list an actual @ .050 duration and some list advertised duration and some list both..
 
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