Into The Unknown

By RYAN MANSON Photography by The Author

urchasing a used engine, be it from a friend, junkyard, or a swap meet, can be a practice in futility. Every small-block at the local high-performance swap meet has been bored and stroked, equipped with a hot cam, and originally resided in a Corvette. At least according to the seller. The truth, however, is usually much less impressive. In reality, that overbore was only applied to one cylinder, that hot cam has two flattened lobes, and the seller actually meant Chevette and not Corvette. The point is, buying a used engine is akin to buying something sight-unseen because though it might be sitting right there in front of you, what’s hiding inside usually can’t be inspected until after the deal is done. And that deal can sometimes burn.

So, what can be done when it comes to buying a used engine? For starters, a heavy education in the make of engine one’s hunting for can help. Most blocks and heads can be identified by a variety of means, be it casting marks (think Camel hump heads) or casting numbers. A quick Interweb search will usually result in a fairly accurate identification that should help persuade, or dissuade, said purchase.

A recent discussion with our buddy Zane Cullen of Cotati Speed Shop brought up this topic spurred by the realization that the mock-up LS engine that they’ve been using in the shop for the last decade-and-a-half might actually hold some performance pedigree. After some quick sleuthing, it was determined that the early LS might have lived its younger days under the hood of a stock car. And by stock car, we mean Stock Car. Back around the turn of the century, American Speed Association (ASA) in conjunction with GM decided to regulate the engines used in the racing series and it just so happened that the guys at The General had the perfect ace in the hole in the form of their LS1 V-8. Spec’d and sealed upon delivery, every car used the same engine with the same tune to create a more perfect form of fairness.

Now, all that sounds well and good, but could Cullen’s LS really be a Sierra Hotel racing engine or is it more likely to be a detuned version of the production engine, which, as it turns out, really did originate from the Corvette? He was determined to find out and dropped the powerplant off at the Clampdown Competition headquarters where it was to be opened up and inspected. What we found surprised us all, to say the least, and should serve as a lesson to all potential engine buyers that you never know what you’re gonna get!

By measuring and inspecting the components on our LS engine, we’ve determined that our engine is indeed within spec of a 5.7L/346ci engine, with the original bore and stroke, camshaft profile, and compression ratio. If any of these dimensions were out of spec, it would be necessary to investigate those components further to determine if it was component-related or point to possible machine work having been made some time in the past. These details give us the information necessary to progress with our rebuild plans, what components need to be replaced, what can be reused, and whether the block and/or heads need to be machined.

2. One of the best methods of identifying engine components is via casting numbers. The block casting number ID’d the LS as a 5.7L/346ci engine from the ’99-00 era. That jives with the specs of the ASA LS1 engines as well as their time frame. This gives us some basic engine parameters (bore and stroke) that we’ll use to compare against our actual findings a little later.

4. Another casting feature further cements its original displacement.

5-7. ASA labeling was present on one cylinder head as well as the oil pan and etched on both heads as well, which made us feel fairly certain about what we were dealing with.

8. After removing the intake, the cathedral intake ports on the heads and knock sensor ports in the valley cover are further indications that we’re dealing with an early LS engine.

9-10. Inspection of the driver side cylinder head reveals a stuck exhaust valve on the number three cylinder that will need to be addressed. The valve sizing comes in at LS spec, 1.55 inch for the exhaust and 1.980 inch for the intake.

11-12. A quick look at the driver side cylinders doesn’t reveal any obvious damage. So far, so good.

13. The camshaft is then removed, followed by the passenger side cylinder head and the rotating assembly to allow for a thorough inspection.

14-15. Before yanking all the pistons, piston-to-deck height is measured and noted. This will help us calculate static compression ratio. We’re right at 0.005 inch above the block’s deck. Coupled with a 0.050-inch head gasket results in 0.045-inch piston-to-head clearance.

16. First things first, we’d like to determine if the bore and stroke are true to stock or if it’s been modified. The pistons measure up with a diameter of 3.8965 inches. That dimension will be compared to the cylinder bores to determine their dimension.

17-18. To measure the cylinder diameter, we’ll be using a dial bore gauge zero’d to the piston’s diameter as measured by a micrometer.

19. Multiple measurements are taken within each cylinder to account for cylinder taper, wear, and so on.

21. Turning our attention to the cylinder heads, we’ve set up a Proform Cylinder Head CC Kit (Summit Racing PN PRO-66831) so that we can measure the volume of the combustion chambers. This will further help us determine static compression ratio.

22-23. The combustion chamber is filled with red-dyed water until it reaches the bottom of the sealing plate.

25. The camshaft doesn’t feature any telltale part numbers, so determining its specs needs to be done manually. Thankfully, this isn’t all that difficult with a degree wheel and a dial indicator. A way to support and turn the cam is a must. Here, we’ve set it up in a lathe between centers, but a pair of V-blocks would work as well. The dial indicator on the cross slide will be used to determine lift by measuring the total amount from the heel of the cam (the backside, flat portion of the lobe) and the nose (the pointy part). Set to zero while on the heel of the lobe, the camshaft is slowly rotated until the dial indicator reads the highest point, giving us total lift. Spec for an ASA camshaft is 0.525 max lift with a 1.7 ratio rocker. This means that we’re looking for a dial indicator reading of around 0.309 inch (0.309×1.7).

26-27. Lift can also be determined by measuring the lobe across the shortest and tallest location and subtracting the smaller number from the larger.

29. Since most camshaft duration companies spec it at 0.050-inch lift, we need to do the same. Starting at the heel of the cam, the camshaft is slowly rotated until the dial indicator reads 0.050 inch, giving us our first data point.

31. Next, the camshaft is rotated until it reaches the opposite side of the lobe from where the first 0.050-inch reading is made.