With today’s digital marketplace, it’s pretty easy to find a new engine for your ride. You’ll find listings for engines advertised as brand-new, lightly used, or our favorite tag, freshly rebuilt. Some of these engines could be great buys while others might be potential disasters.
The best way to know for sure is to check out the engine in person. That’s not always possible—your perfect engine may be too far away from home base to make the trip. On the other hand, you sure don’t want to lose out on a potentially good powerplant. It’s definitely a conundrum.
But let’s say you take the risk and buy an engine sight-unseen. You put down the cash and the engine arrives on your doorstep in a week or two. The urge to drop it into the car and motor away is strong, but it’s not the smart play. A better plan is to bolt the engine on a stand and give it the once-over. Finding an issue and fixing it before the engine is in the car or fired up on a test stand will save a lot of heartache.
Based on my years of experience with hot street and drag race engines, I’ve come up with some things to check and to look out for. This is by no means an exhaustive list, but if an engine “passes” these inspections, you can be pretty confident it’s a good one.
External Inspection
Go over the externals of the engine first. Make sure you got everything the engine was advertised as having–induction system, ignition components, headers, accessories, etc. Also check for things like dented valve covers, a bashed-in oil pan, or other damage that indicates the engine was dropped or otherwise abused. Damage like this usually happens during shipping, and the seller should be made aware.
Look for evidence of coolant, oil, and fuel leaks. An LED flashlight is your friend here. Check for sloppy assembly techniques like RTV sealant oozing out of the intake manifold ends and loose or missing fasteners. These may be simple oversights or clues that the engine may not have been assembled with the best of care.
If the engine was advertised as a runner, remove the headers or manifolds and check the color of the exhaust ports. Black indicates an over-rich condition. White points to a lean condition, and black residue could mean oil is getting past the piston rings in the cylinder(s).
Leakdown Test
Doing a leakdown test is pretty important. You want to see consistent leakdown rates between cylinders. If one or more cylinders have a higher leakdown rate than the others, there’s a good chance the piston rings are worn or the cylinder bore is damaged. At this point, you should remove the cylinder heads and have a closer look. The only real cost here are some gaskets.
A leakdown test is usually done with the engine warm as it will be close to operating temperature, but you can perform one on a cold engine. Just keep in mind leakdown rates for a cold engine will be higher simply because parts contract.
A leakdown test can also pinpoint other engine issues like bad or broken valves. This OnAllCylinders leakdown test story has the details.
Valvetrain Inspection
I like to begin inspecting the valvetrain by checking valve lash. It’s pretty easy to do with a cold engine on an engine stand. Lash that is not to spec can indicate an issue like a bent valve or a broken lifter.
Examine the valve springs. Per COMP Cams:
“Check for coil bind. This means that when the valve is fully open, there must be a minimum of .060” clearance between the coils of both the inner and outer springs. If this clearance does not exist, you must change either the retainer or the valve to gain more installed height or change to a spring that will handle more lift or machine the spring seat for extra depth.”
“Always check for clearance between the retainer and the inside face of the rocker arm. This will be most evident while the valve is on the seat. Rocker arms are designed to clear specific spring diameters and require a proper rocker arm/retainer combination. Improper clearance can also be the result of improper rocker geometry and may be corrected with different length pushrods or a different length valve.”
Next up, check valve spring pressure. The pressure numbers should match up closely to the engine specs. Huge differences in spring pressure will give you some pretty good insight into the health of (or more correctly, lack of it) the engine.
Look to see if the valve stem seals are in place. Reason is, some drag race engine builders like to use seals on the intake valves only and not the exhaust. The idea is the exhaust valves are exposed to a lot of heat, and not using seals provides some extra clearance for oil to reach the stems and guides for lubrication and cooling. With no seals on the exhaust, you can also check to see if the cylinder heads have bronze guides.
Something I like to check is rocker arm sweep. What you’re looking for is a pattern that is narrow and centered on the valve stem. This usually points to a correct choice of components. Too short a rocker pivot length and the rocker will sweep inboard of the center. Too long a rocker pivot length and the rocker will sweep outboard of the center.
It’s a good idea to pull a pushrod or two and examine them. They shouldn’t be bent, obviously, but also check the tips. Worn or damaged tips are a warning sign something is amiss.
Bottom End Inspection
Now it’s time to turn your attention to the bottom end. You’ll have to remove the oil pan, but the cost of a new pan gasket is cheap compared to a potential bottom end failure.
Closely examine the reciprocating assembly. You’ll be able to see if heavy metal was added to the crankshaft if a lot of extra balance holes were drilled in it for balancing. I’ve seen cranks with incorrect balance weights installed (basically junk metal was used). You’ll also be able to see what the cylinder bores look like from the bottom up. If there’s a piston or ring problem, it will show up on the cylinder wall.
Pull one main cap and have a look at the bearing. Spin the engine over to where you can inspect at least one rod bearing. Scuffed or worn bearing surfaces will tell you immediately how fresh the engine and if you got what you paid for.
Hopefully your inspection found no major issues. Fingers crossed you got a great deal on the engine!
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