Why advance cam timing

Simply add the two numbers together and divide by 2. The equation would be:. That means that the exhaust centerline has advanced 10 degrees because the difference between the LSA and the intake centerline is 5 degrees.

Placing the exhaust lobe centerline at degrees puts the numbers in place:. Since a DOHC engine uses a separate intake and exhaust camshaft, this allows engineers to move the intake and exhaust lobes separately. So now with hydraulic adjusters, the ECU can move either cam separately to advance or retard the intake or exhaust.

Then, somewhere in the midrange when the engine would really respond to lots of overlap, they begin to retard the exhaust to create more overlap. In reality, most of the DOHC engines only move the exhaust lobe for emission reasons.

This is probably more than you wanted to know about camshaft positioning, but this might come in useful at some point. If nothing else, you can use it to dazzle your friends with you incredibly acute knowledge of camshafts and how they work. Or maybe not…. I advance to keep the RPMs down and keep from blowing my motor! Works like a charm, and lowers the shift point so the torque curve is there in an instant! Consider this: a small shop does not have the resources a bigger shop has.

That is not correct, doing that would make the idle rougher. What you describe here would reduce the LSA increase the valve overlap and make it idle rougher. Jeremy — You are absolutely correct. In my haste to write this — I have it backwards. Like if your timing is set at 32 degrees straight up would it change it to 34?

Also should the timing be adjusted at all with a cam that's been advanced? Re: Advantages of advancing the cam on a street engine? Most all catalog cams are manufacured so that they are 4 to 5deg advanced when installed with a normal timing gear set.

Your cam is probabily already "advanced". You have to degree the cam to know where it is now in order to move it with any accuracy. The multiple keay way timing gears are not necessarily going to move the cam by 4deg or 8deg as marked. Ignition timing is set independently. Yes you would need to readjust the spark timing using a timing light. As a general trend advancing the cam tends to add a bit of bottom end torque by closing the intake valve a bit earlier.

Its just rocks the torque curve a bit. Biasing the low end of the rpm range usually at th cost of a bit of top end. There are many other factors. Same with gas mileage. There many factors. Any real in car gain-loss in performance wether its quicker acceleration or better net fuel mileage can only be determined by accurate A-B testing.

Post by roadrunner » Thu Apr 26, am I played around with the camshaft timing on my cleveland some years ago, degree cam advertised , performer manifold, running l. Advancing the cam degrees gave back some bottom end, not a lot but then I had to retard ignition timing to avoid pinging, retarding the cam degrees gave a better top end to , with no ignition retard required.

I tried open chamber and closed heads on this engine, the closed chamber heads were miles ahead as far as pre-ignition goes, what compression ratio are you running? As he mentioned, you can't assume the multi-keyway sets are correct. Not too long ago, I used one of the more expensive Cloyes sets with 9 positions - varied all over the damn map from their labeling. It's the stock cam used in the hp 69 's I've got a degree wheel coming from summit to degree it. Compression is 9 to 1. So for longevity because of the pinging I would see better advantage running straight up?

This is my current set up right now. Scavenging is using the out-flowing exhaust to help draw in the next intake charge partially causing lumpy idle. The incoming cold air and fuel cools down the outgoing exhaust charge, condensing the exhaust gasses. This is VERY counter-productive in a turbo application since the engine needs no help from scavenging to fill the cylinder. I've heard this being called "turbo chill". Cool, condensed gasses in the same space push less hard on the turbo, causing lag.

HOT gasses are better at spooling the turbo, thus the advanced exhaust timing to open the valve sooner in the power stroke. This steals some of those hot, expanding exhaust gasses to help spin the turbo a little faster. The retarded intake just helps cut down the overlap further. Retarding overall cam timing: Retarding overall cam timing is better for high-RPM power.

For some reason a lot of guys think that if their cam is advanced or retarded a few degrees that it affects their ignition timing. Nothing could be further from the truth. Regardless of where the cam is "phased" in relationship to the crank, you can always rotate the distributor to achieve the ignition timing you want to have.

Ignition timing only controls when the spark plug ignites. Usually the magic number is between 34 and 36 degrees, but every engine is different, and every type and brand of fuel is different, etc, so every engine will like timing in a slightly different place than another.

Advancing the spark timing creates a better burn and more cylinder pressure. You can only advance the timing just so far though before the fuel burn becomes and uncontrolled burn or "explosion" detonation or "pinging" , which can cause serious damage to pistons, rings, head gaskets, etc. The type of material the heads are made out of also have an effect on timing and detonation, such as cast iron vs.

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.