Pretesting rebuilt engines can help cut down warranty issues

Why is pretesting your engine work so important. Many warranty issues can be avoided.

This is just a little story about some of my experiences while managing a production engine and custom rebuilding shop. What I wanted to share is some of the ways you knew your shop was doing quality work for your own piece of mind. Knowing you did quality work did not always transfer to the customer who may have been having a problem. One of the hardest things for anyone to do is admit he or she could be wrong. I was also in charge of the warranty department as well and had to bite my tongue many times over the years. This will be short as I could go on forever about the  story’s from the last 40 years and I do have many.

Anyway for this story lets skip to the last 10 years to save time. We all know that quality is number one in most business and warranty costs come right off the bottom line. For this reason we decided to add a new machine to our shop for engine testing to take our quality to the next level.

Engine Tester
Engine Tester

The Sim-Tester Quality Control engine test station. This machine does a number of tests and allows you to add options as well. In addition to checking for lubrication issues, the Sim-Tester can help kick start the break-in procedure with special additives added to the testing oil. Here is a quick list of testing that was done and you can see very quickly how this would solve or help you find possible issues.

All engines were tested prior to delivery for these issues:

Oil Pressure

Oil is preheated to 135 degrees. The oil is filtered three times, first with filter media in the oil catch tray, second a five micron filter, third a twenty-five micron filter. An oil pressure test is done as well.

Oil Flow

This two step process indicates any reason for excessive internal oil leakage, possible causes could be excessive bearing clearance, leaking or missing plugs, improperly installed cam bearings etc. We would visually inspect for excessive oil bleed off.

Rotational Torque

This was checked at varying engine speeds. Every engine has internal friction. We would record the amount of amperage required to rotate the engine and watch for torque spikes during rotation.

Valve Adjustment

During the rotational test the hydraulic lifters are checked to insure that the lifter plunger is adjusted properly, the lifter is filled with oil and has been purged of all air. Mechanical valve adjustments are reset with the engine rotating. Lifters are checked for rotation ( Flat tappet lifters must rotate or the lobes will go flat ) Rocker arm oiling is confirmed.

Compression Test

A cranking compression test is done.

Cylinder Leak Down Test

A leakage test can also be used in conjunction with a compression test to diagnose other kinds of problems. A cylinder that has poor compression but minimal leakage usually has a valve train problem such as a worn cam lobe, broken valve spring, collapsed lifter, bent push rod, etc. If all the cylinders have low compression but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.

Bolt Torquing

All torqued fasteners on your engine are first checked by the assembler and second by the quality control tester. On torque to yield bolts they do not yield the bolts twice.



So there you have it, many issues are covered by this testing and now you have some facts to go back to your customer with if you ever have to.  ( AND YOU WILL ) Some of you have been on either side of the fence and have had to deal with these issues. What you do or did with that info is going to be different for every instance but at least you have some facts to base your decisions on. Sometimes its hard to say but, Remember the customer is always right.

Some of the phone calls I have received and had to deal with:

I just installed one of your engines and have no oil pressure. Now what!

  • On your end you know it had oil pressure when it was tested and now you have to ask the installer ( that usually says he has been doing this for 20 years ) Did you install the oil pump drive or pick up screen ? Do you have oil in it ? Is the gauge and sensor working ?

I just installed one of your engines and it is seized, starter will not turn it over!

  • On your end you know the rotational torque test was good. You ask the customer if he has oil in it. Is the starter and battery good? Did he try and turn it over by hand? Is one of the torque converted bolts too long?

I just installed one of your engines and the lifters are ticking!

  • When it left your building it tested good. You ask, Is there oil in it ? By now you can tell by the customers comments he is not happy ( that usually says he has been doing this for 20 years ).

I just installed one of your engines and have no compression on one cylinder! ( Or many cylinders )

  • Rebuilt Engine
    Rebuilt Engine

    Again you know it was fine when it left your building. Depending on the engine your questions may vary. Rebuilt Engines usually do not come with manifolds on and you have to swap them over from the original engine. So was the engine a gm 3.1 or 3.4 where you had to remove the push rods to get the intake gasket in? Did the customer mix up the push-rods as exhaust and intake are different lengths? Was it a 360-390 or FE series ford and you have to remove the push rods to install the intake manifold? Was it a 350 gm and the customer either left off the washers or had too long a bolts for the intake manifold? If too long, the center intake bolts line up with the push rods and can make a ticking like a bad lifter or even stop the movement of the valve train causing no compression. This was so common at one point that if someone had a tick on a small block gm, I would get them to come down and let me hear it. I would have a wrench in my pocket and while running I would back off the intake bolts and actually hear the noise disappear. Install a washer under the bolt and they were good to go.

So there are just some of the issues you can have. The hard part is getting the customer to actually understand why you are asking those questions. Most of the time they are defensive. In the end I found more customers looking for complete engines with everything on to eliminate installation problems. Some would only install used engines for that reason as well. This is one of my short stories and like I said I will throw one in every once in a while. Any comments from either end are welcomed.


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