Читать книгу Chrysler Slant Six Engines - Doug Dutra - Страница 11

CHAPTER 2

ENGINE TUNING, EVALUATION, AND DIAGNOSIS

The Chrysler Slant Six is a well-designed engine that can take lots of hard use, so you want to carefully evaluate any engine before taking it apart for rebuilding. Evaluation of a nonrunning engine is limited. You should do everything possible to get the engine running. If the engine is already out of the vehicle and still assembled, check the following:

• Was the engine stored indoors, kept well covered, and kept dry?

• Are there any obvious cracks or physical damage, such as a damaged oil pan, damaged valve cover, bent flex plate, broken casting ears, stripped bolt hole(s), or rusty water drip marks?

• Is the motor oil still inside, and is it clean? Cut open the oil filter if it is still present.

• Remove the spark plugs. Are any of the spark plug tips damaged or rusty?

• Attempt to turn the engine over with a wrench. Does it turn over freely?

This engine is mostly complete and turns over with a wrench. It has rags plugging the openings and was kept dry, so it looks like a pretty good core for rebuilding.

The passenger’s side of the engine shows that the oil filter and distributor’s splash shield are still attached. The engine’s build number stamping is present, and we see the original factory embossed steel head gasket, which indicates that this engine has never been disassembled.

The Slant Six vibration damper is a press fit, so there is no large center bolt present. Install a 3/8-16 hex-head bolt in one of the outer tapped damper holes if you need a way to rotate the engine with a wrench.

Finding any of the listed issues makes a “good running engine” suspect. Any loose engine you find that is seized up, shows a lot of metal in the oil filter, or has physical damage does not qualify as a good core for rebuilding. Try to avoid these. Skip forward to the engine inspection chapter if the engine you find has already been disassembled.

This engine core had green coolant running out of it, which is a good indication that the cooling system was maintained. Engines that were run for long periods on water alone will need additional water jacket cleaning.

Tech Tip

Check the fuel quality before attempting to start any vehicle that has not run in more than 90 days. Gasoline absorbs moisture and goes bad (turns into varnish) over time. If in doubt, drain and refill the gas tank or connect a separate gas can so you run the engine on good fuel. ■

Tech Tip

Remove the fan belts and momentarily run the engine to test for accessory noises. ■

There are many additional checks and tests that can be done to a running engine. Try to get the engine to run, especially if it is still in a vehicle. If the engine will not turn over or run, perform the checks at the beginning of this chapter to get some idea of whether it is a candidate for rebuilding. If the engine runs, check the following:

• Will the engine stay running at lower RPM?

• Do you have oil pressure? Does the engine overheat at idle?

• Does the engine miss, run roughly, or backfire?

• Is there excessive smoke? If so, what color (white, black, blue)?

• Are there oil, fuel, or water leaks?

• Do you hear any loud noises? If so, in what area of the engine (up high or lower down)?

If a Slant Six engine stays running, has oil pressure, does not make loud knocking noises, and does not quickly overheat at idle, you should fix any obvious leaks or problems. The next step in the evaluation process is to pull off the valve cover to check and adjust the valve clearances.

If the engine runs fine but has excessive blue tailpipe smoke, oil consumption, bad oil leakage, or loud knocking noises, check the following items before deciding to pull the engine for rebuilding:

Excessive blue tailpipe smoke:

• Is the crankcase oil level too high? Check to see if the dipstick is the correct length.

• Does the engine have a clogged or incorrect PCV valve?

• Is the incorrect carburetor base to intake manifold gasket installed?

• Is the carburetor base gasket reversed and blocking the PCV port?

• Is the intake manifold PCV port or hose clogged?

Excessive black tailpipe smoke:

• Does the engine have a misadjusted or sticking choke?

• Does it have a misadjusted or malfunctioning carburetor?

• Is the PCV valve clogged or incorrect?

• Has excessive fuel diluted into the engine oil?

High oil consumption:

• Is the crankcase oil level too high?

• Is the PCV valve clogged or incorrect?

• Is the oil pressure sending unit leaking?

• Are there plugged or sticky piston oil control rings?

Excess oil leakage:

• Is the crankcase oil level too high?

• Is the oil pressure sending unit leaking?

• Have old or split spark plug tube O-rings and/or damaged spark plug tubes been changed?

• Are the oil pan or valve cover bolts loose?

• Is the oil pan drain plug loose?

Loud knocking noises:

• Are there any loose torque converter flex plate bolts (automatic transmission only)?

• Are there any worn or failing accessories (water pump, alternator, power steering, or fuel pump)?

Mechanical Lifter Valve Lash

Slant Six engines produced until 1981 used solid lifters and adjustable rocker arms to open and close the valves. There is a small amount of clearance, called lash, designed into this system, and those settings (different clearances for intake valves versus exhaust valves) must be initially set and then periodically checked and adjusted during the life of the engine.

Correct valve lash adjustment ensures smooth, quiet, and trouble-free operation. Valve seat recession will reduce valve lash clearance and engine performance declines. The valvetrain becomes noisy as the valve clearances become wider with wear. If the lash is insufficient, the engine misses or the idle becomes rough, and you risk burning the exhaust valves.

The valve lash clearances are crucial to solid lifter engine performance and smooth operation, so it is the first thing that should be checked and adjusted when troubleshooting or tuning a pre-1981 Slant Six. The job of lashing valves sounds intimidating, especially to the novice mechanic, but it is a straightforward process that uses common hand tools. It can easily be performed in a couple of hours. The end results will be:

• Improved engine performance and economy