I've just finished replacing intake manifold gaskets on a 1996 Blazer. I have noticed that some posts mention getting the cam retard checked and adjusted to 0 degrees. My Blazer seems to run fine and didn't set any codes when started; would it make sense to have it checked? What's a normal charge for checking/adjusting cam retard?

 

I just did mine as well and Captain Hook on here told me about the cam retard. Look at my thread...Intake Manifold Gasket Help. That might help. The only thing I know is that it is inside the timing cover and if your vehicle is running fine I wouldn't mess with it.

 

Prolly not inside thefront cover. Its inside the distributor at the bottom.

 

Camshaft retard, (also referred to as CMP retard) in my opinion, is a misleading term for what the adjustment actually does. The camshaft position sensor is mounted inside the distributor. Slightly rotating the distributor aligns the camshaft position sensor with the camshaft, (that's how the sensor got its name). As far as I'm concerned, the adjustment should be called "camshaft position sensor alignment, but, GM didn't ask me, so I'm just trying to make it easier for you to understand what it is, what it does, and why it's so important that it's correct.

When the distributor gear is not meshed correctly with the camshaft gear: After the engine is running, the check engine light will immediately come on, and P1345 will be set in memory as a hard fault. If you've got it meshed correctly, there will be no P1345 in memory BUT, that doesn't necessarily mean camshaft retard is correct. The DTC will be set only when camshaft retard is off by ~27 degrees, or more, (one tooth or more off).

Camshaft retard data, along with crankshaft position sensor data, is used by the PCM for accurately detecting and identifying cylinder misfire. If camshaft retard is not within specs, misfire data will not be correct.

Spec is zero degrees, (perfectly aligned) with a tolerance of plus or minus 2 degrees. It requires a "high end" scan tool capable of accessing live streaming camshaft retard data to check and adjust it. The el cheapo $500 scan tools can not access the data. The outside diameter of the distributor base is slightly smaller than the inside diameter of the hole in the intake manifold. This allows the distributor to rotate, more or less on an arc. The factory distributor hold down bracket will allow about 15 degrees of total adjustment. If that's not enough to get it within spec, remove and discard the bracket and use an old style SBC, (Small Block Chev) bracket, (Mr. Gasket #1009 ~$5). This will make camshaft retard fully adjustable.

Simultaneously when aligning the sensor with the camshaft, the rotor segment is also aligned with each corresponding terminal inside the cap when each cylinder is fired. This keeps the air gap between the rotor segment and the cap terminal, to a minimum. This reduces/eliminates crossfire inside the cap.

If camshaft retard is off, lets say 20 degrees, there will be no DTC in memory, and no check engine light, however, there will be some serious crossfire going on inside the cap, which will cause cylinder misfires. On top of that, the PCM has no way to accurately detect or identify which cylinder(s) is/are misfiring. The PCM "knows" somebody isn't playing nice, so it takes a wild guess and sets P0300 through P0306. This will send you on a wild goose chase trying to figure out who's not playing nice

Rotating the distributor on this engine does not affect ignition timing. There are three common methods to generate a pulse for the primary ignition system: Older vehicles, with distributors, either had ignition points and a cam block on the distributor shaft, or a pick up coil and reluctor wheel inside the distributor. Rotating the distributor would change the position of the points or pick up coil, causing the ignition coil to fire earlier or later, (advanced or retarded). The other method for generating a pulse is with a crankshaft position sensor and a reluctor wheel on the crankshaft. This is what 1996 and newer 4.3's use. The sensor is mounted to the timing cover and does not move. It sends a pulse to the PCM when each piston is at top dead center, (TDC). The PCM calculates what the ignition timing needs to be, and it sends a modified pulse to the ignition module, which in turn fires the ignition coil. The PCM has full control of ignition timing advance, and it is not adjustable.

When camshaft retard is adjusted properly, you can unplug the camshaft position sensor and the engine will start and run. Engine performance will not be affected. There will be no misfire detection, and it will set a DTC for the sensor, but it will perform perfectly fine. The camshaft position sensor can not cause a no-start condition.

Bottom line, if the distributor hold down bolt is loosened or removed, camshaft retard needs to be checked, and adjusted if necessary.

Hope this helps.