If you find extra lash on...
If you find extra lash on any valve, its critical to find the cause. Extended lash on a single valve puts tremendous strain on your entire valvetrain.
The needle bearings on this...
The needle bearings on this shaft-mounted rocker arm went bad and were not caught in time. This caused the axle to wear, which eventually broke the rocker.
The tie-bar connecting this...
The tie-bar connecting this roller lifter to its mate broke, allowing the lifter to spin. When that happened the cam lobe smashed the lifter face, locking the roller tight.
Debris in the grooves of your...
Debris in the grooves of your belt pulleys can cause vibrations powerful enough to break brackets right off the engine. The pulleys are easy to clean, and you dont have to have them off the engine to do it.
A worn throttle shaft can...
A worn throttle shaft can cause your carburetor to hang up. If that happens you are probably going to wind up getting hurt, and you definitely are going to hurt your car. Checking for wear is simple; just wiggle the shaft to see if it has excessive play.
I often get calls on Thursday or Friday morning from customers who changed their oil the night before and found debris in the filter. They are concerned about the health of their engineand they should bebut unfortunately, Friday is a little bit late to be tearing it down if you are trying to make an event on Saturday. Thats why I recommend a regular schedule of some very easy engine checks to keep you running week after week. The sooner you do this the better, so in honor of the Saturday-night racer, Ive named this program Monday Night Maintenance.
At The Track
There are a number of things you can evaluate based on your performance at the track. First of all, how was your engines performance? Was it good off the corners? Down the chutes? Next, were there any problems, especially weird noises, overheating, vibrations or missed gears where the engine might have been over-revved? If there was a crash and you spun the car, a lot of times the engine gets run backward. A lot of things that can happen at the track can set off warning bells you should follow up on when you do your weekly maintenance.
Begin your Monday night maintenance with an inspection of the oil filter. With dry-sump cars you have a screen filter on the scavenge side of the pump that makes inspection easy. The same thing can be done on a wet-sump engine. You can take a paper filter apart, but its a little bit messier. You may only want to do this every other week or so.
Check the filter for foreign materials, especially metal shavings. This will tell you if there is anything going on inside the engine that shouldnt be. You can also determine from the materials properties where you should start looking for problems. First, look to see whether the particles are metallic. This may sound obvious, but if you have aluminum-colored material and its not metallic, its probably aluminum. If you are running cast-iron heads and a steel pan, theres not much left thats aluminum but the pistons. But before you start tearing everything down, take a look at the spark plugs. If one varies from the rest, that can tip you off which piston might be damaged.
Also, if you have a bronze distributor gear you may confuse material in the filter that came from the gear for a problem with the bearings. If you are running a wet-sump engine you are going to have distributor gear wear, so be mindful of it. Knowing whats in your engine will help you know what you are looking at when you find material in your oil filter.
Assuming you dont have any major concerns after your oil filter inspection, the next thing to check is valve lash. This is critical because it can let you know if there are any problems with anything in the entire valvetrain. If youve got more than .003 to .004 of an inch lash more than is recommended, theres quite likely a problem with the lifter, the cam, the rocker arm or the pushrod.
Say youve got one valve thats .005 or .006 looser than it should be. Rotate the engine over to see if it has a tight or loose spot in it. If you find nothing, then adjust it and rotate the engine again. If it has changed after the adjustment that definitely means something is going on. The lifter might be rotating or any number of things; its time to dissect the engine until you find the source of the problem.
If you think there is something going on, start with the rocker arm since its the first thing you come to anyway. Put some pressure on the roller tip to make sure there is no roughness in the motion. If its a shaft-mounted rocker do the same thing there. Roll the rocker against the rocker shaft. If there is any roughness you can disassemble those easily to check for deterioration of the axle or bearing. No roughness should be allowed in either the movement of the roller tip or the rocker over the shaft.
The pushrod is the next thing in line. Check it for deterioration, wear, chipping or anything on the tip. Then check each rod for straightness. This can be done by rolling it along a surface plate or even a pane of glass, anything you know is flat.
With the pushrods out, shine a light down in the valley. If you are running roller tappets look for obvious things like broken tie bars, which will allow the lifters to rotate. Also look for foreign materials or signs of excessive wear.
If you dont see anything and are still worried that there is a problem, go ahead and take off the intake so you can get at the lifters. If you are using roller tappets, check them just like the rocker arms. Apply pressure to the roller and make sure it rolls smoothly. Also make sure there is no movement of the roller, either up-and-down or side-to-side. Flat tappets are easy to check without disassembly if you are concerned about wear. Put a mark you can identifty on the pushrods, spin the engine over and watch to make sure the pushrods rotate. If the pushrods do not rotate, then be assured that the cam and lifters are wearing. A cam lobe has taper in it, and the lifter has a crown to make it rotate. So when that crown or taper is gone because of wear, the lifters wont rotate and the wear will just get worse. This check is a good procedure to do even when the engine is new.
If the engine is allowed to run with excessive lash, a catastrophic failure is bound to happen. Even if just one valve is out of tolerance, the loading on every valve, every lifter and every valvespring increases tremendously. If the lash is too tight, that usually indicates a problem with the valve or the valve seat. It may be a case of the valve tuliping into the pocket. That can be caused by overheating, which may be the result of a too-lean condition or too much timing. Other factors that can cause the valve or seat to pound themselves out of shape are certain fuelsespecially unleaded fuelsoil contamination and valve and seat materials that are incompatible with each other (this is usually only a problem with more exotic materials). Finally, weak valvesprings can also be the culprit. If you break an inner spring and lose 30 percent of your tension, then thats going to give you a slingshot effect. The cam is going to want to throw that lifter and valve, and then its going to hammer back down on the seat.
Lets say everything has been good up until now. The valve lash is OK and you havent noticed any other problems. Valvesprings should be next on your list. There are many methods to check the valvesprings while still on the car, but the only thing thats really important is that your method is consistent and you get a good baseline for comparison. Check the springs the first time you put them on your engine, and if you want, write the numbers you get right on the head. Check with your engine builder for recommendations, but as long as the springs stay within about five percent of their original tension then you are probably OK. The bigger problem you are likely to run into is you will have seven springs that originally rated at 230 pounds check out at 225 and one that registers 210. You may have a broken inner spring or dampener, or you may have just had a spring go soft. Its common practice in this situation to replace all the springs, but many times when weve had one spring go bad weve replaced just that spring and the engine has run fine. It all depends on how long you have been running that set of springs and the way the rest of the engine looks.
Ive seen a lot of occasions where belts cause a catastrophic failure. Sure, they can fail at any time, but you can lessen that chance with a weekly inspection. Check to see if the tension is right and if any of the belts are frayed or nicked. Also for oval-track engines, the grooves in the cogs can become contaminated with rubber, asphalt, dirt and mud. Ive seen oil-pump belts dancing like a roller coaster, and its just because its got something in the grooves. Ive even seen oil-pump mounts break because of the vibration it causes. So keep an eye on the belts and keep the pulleys cleaned out.
The Other Stuff
Finally, while you are doing all this stuff, keep an eye out for the common-sense things. Inspect your valve-cover gaskets, look for oil leaks, damage to headers or tailpipes, even loose bolts. Pull the spark plugs and check them. You dont have to be qualified to read plugs for tuning, just look for variations from cylinder to cylinder, or anything crazy like contact with a piston top or an oil leak in a single cylinder. That can tip you off to problems you might have missed. And since you have your plugs out, check your plug wires. Check out all the boots and the distributor cap.
This list is just a guideline. If you have had consistent problems that have knocked you out of races, add them to your routine. If you did a survey of everybody who races, from Hobby Stocks on up to Winston Cup, its amazing how often people will fall out of a race with a problem thats awfully easy to avoid. A weekly routine of Monday-night maintenance can help keep you in the game.