Should i advance my cam

If we keep duration at a constant, a wider LSA will give an engine more peak power, a rougher idle, more torque at lower rpm, and peak power also occurring at a lower rpm. Not only will a wider LSA give you the aforementioned qualities, but it also results in less cylinder pressure, which is great for higher compression street engines. This is also known as Lobe Center Angle, and is the crankshaft degrees that are measured when the intake and exhaust valves are both open.

This "overlap" occurs at the end of the exhaust stroke and at the beginning of the intake stroke. When an engine is running, the exhaust valve needs to stay open slightly after the piston passes top dead center. This helps keep the momentum of the exiting exhaust gases to maximize the amount of exhaust gas pulled out scavenged from the cylinder. The intake valve on the other hand, opens before top dead center, and uses the momentum of the exiting exhaust gas to start pulling the intake charge into the cylinder.

More is not always better, as too large of a lobe center angle can result in too little overlap to make good power. Too little overlap causes the lack of complete expulsion of the exhaust gases, and less intake charge filling the cylinder. Smaller amounts of overlap produce a smoother idle, and a slight benefit in top end horsepower.

This effect on performance is directly linked to engine rpm. Higher engine speed causes greater exhaust-gas velocity, which relates to greater momentum of the exiting exhaust gases. This is why a longer-duration camshaft produces power higher in the rpm range. It also causes the loss of low rpm power and economy that larger cams experience. But at higher engine speeds these conditions are minimized due to the slight lag time it takes to get the intake charge moving into the cylinder.

The cam's centerline is used to correlate valve timing to the crankshaft's rotation. This is again measured in crankshaft degrees. Centerline is explained as the number of degrees that the crankshaft must rotate from top dead center until the cam has rotated to the peak or centerline of a given intake or exhaust lobe. For the engine to run at peak performance, the valves must open and close at the correct time in relation to the piston's position and the crankshaft's speed.

The intake centerline is the point of highest lift on the intake lobe. The exhaust centerline is the point of highest lift on the exhaust lobe. The cam centerline is the point halfway between the intake and exhaust centerlines.

Close Ad. Join MotorTrend. It's also relevant to the static compression, the effective compression based on the cam profile, power adders, etc. When detonation happens, it is more of an out of control explosion. All you did was put a great big dent in the back of your car.

That is what happens when detonation happens inside a cylinder So you can only go just so far on the timing before you have detonation, and when detonation happens, it's like smacking the top of the piston with a sledge hammer rather than pushing on it with a smooth - controlled burn.

Retarding the timing does the complete opposite. Because the burn is lighting later and the pressure is lower, the burn happens MUCH too slow.

In fact, it is still burning when the exhaust valve opens, which is why when your timing is too late, your headers will glow cherry red and your water temperature goes up.

It's also why your engine becomes a complete turd and has no power. This is why you run advance in your ignition timing, but again, it has nothing to do with cam timing. On the flip side, an engine with not enough compression and too much octane will burn too slow and too cool, and will want more timing advance to help get it out of its own way. This is why rookies that run their cars at the race track with their mildly modified engines trying to run "race fuel" thinking they'll go faster, end-up going slower.

They don't have enough static compression or ignition timing to get enough energy out of that fuel with too much octane. The trick is to have a matched amount of static compression, effective compression, etc. Remember me. Log in. Forgot password or user name?

To advance the cam or not to advance the cam, that is the question. Previous 1 2 template Next. Posts Latest Activity Photos. Page of 2. Filtered by:.

February 1, , PM. On my Skylark I'm trying to think of changes to make to it with out actually having to do any major lifting. I'm real happy how the car runs right now, but it seems like at 6, rpm it's still pulling for more and with the fact I've left the bottom essentially stock I'm thinking of getting an adjustable timing set and advancing the cam. Here is the rub though, do to the rush of getting ready for Drag Week and not having an adjustable timing gear even if I did find it off I didn't degree it when I popped it in.

Does that sound reasonable or should I leave it alone? Second part is I want to chassis dyno it at some point this year. Do to where I live I'd kinda like to only do it once, so should I do it before moving it and expect the power curve to simply move downwards, or should I advance the cam first and if it noses over on the dyno simply move the cam timing back?

Or am I simply stuck dynoing a before and after remembering its easy to spend other peoples money. I'm not sure there would be a down side to advancing the cam from where it sits now. It makes power above the rpm I'm willing to turn it and it can run on 87 octane now so if the DCR goes up I may have to run a higher grade gas, and as long as it's 91 or lower I'm okay with that too.

Is there a downside I'm not aware of? Tags: None. You could take a before and after compression test and post those numbers up so we can see what they are.

Comment Post Cancel. Barry Donovan.