How to Build a 383 Small-Block Engine - Sledgehammer

Building a budget-friendly 383 stroker for Lethal Weapon with Lunati and Comp Cams for our AntiVenom Engine Build.

Justin Cesler Jan 16, 2014 0 Comment(s)
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It’s been a little while since GMHTP last built a “traditional” small-block, but it’s certainly not because we don’t still enjoy small-block Chevy technology. The engine platform is tough, the parts are affordable, and the power and reliability is hard to beat. When Steve Baur, an old GMHTP associate and current office instigator, finally scored a clean ’87 Firebird Formula 350, we started dreaming up engine combinations right away, and when his stock TPI 350 rattled its way off the trailer, we knew exactly where to start…the engine.

However, we didn’t want to tear into the stock 350 right off the bat and leave the shell of the car sitting abandoned somewhere while we bolted a new heart together. Instead, we chose to build an all-new small-block from scratch, using high-performance internals stuffed inside a four-bolt main, one-piece sealed, 350 block that would take a ton of abuse without any issue. It wasn’t particularly hard to find one and when we finally dug it out from Greg Lovell’s shop, we were impressed. Plucked from a bread truck some 10 years ago, the 350 block was in great shape and had the main caps that every small-block builder was looking for. Of course, we weren’t planning on keeping the cubic-inches stock either, but we could have with how good the cylinder walls looked.

If you’re starting to think you’ve read this before, you may remember that we’ve covered this project already in an earlier issue, where we waxed nostalgic about the good ol’ days, showed off Steve’s super clean Formula, and introduced the Lunati Sledgehammer 383 cubic-inch rotating assembly that we were planning to use. After a small struggle trying to find a machine shop that wasn’t backed up (good luck with that!), we were finally able to drop our 350 off to be cleaned, decked, bored, and put together. This month our focus was on bolting the bottom end together and installing the camshaft. Follow along to watch Greg Lovell kick it old school as he puts together an SBC the way they used to do it.

350 Block 2/28

1 Our engine build began with a low-mileage four-bolt 350 block that hoarder extraordinaire Greg Lovell cherry picked from a bread truck several years ago. After sending it through the hot tank, we dropped it off at a local machine shop…

383 Machining 3/28

2 …who performed the basic machining necessary for a 383 build. The stock bores were bored .030-inches over to match our Lunati pistons, the surface of the block was decked, and the block was notched to clear the large throw stroker crankshaft.

383 Engine Block Before 4/28

3a Additionally, the machine shop installed a new set of freeze plugs and camshaft bearings to get our block up to par.

Freeze 5/28

3b For under 400 bucks ($387.34 to be exact) we had a quality four-bolt block ready to accept the new rotating assembly.

Lunati Sledgehammer Rotating Assembly 6/28

4 We covered the components involved in the 383 build in the last issue of GMHTP, but for those of you who haven’t been following along (for shame!), we selected Lunati’s Sledgehammer 383 rotating assembly, which includes a 3.75-inch crankshaft, 6-inch H-beam connecting rods, and a set of 4.030-inch Pro-Tru pistons.

Spiro 7/28

5 Greg Lovell of AntiVenom wasted no time getting started and began the engine assembly by installing a Spiro lock into one side of the piston. If you’ve never built an engine before, get ready to fight with these at first, and make sure you install them all the way before dropping a slug into the block.

Chrome Moly 8/28

6 With a lock on one side, Greg slid the chrome-moly wristpin in place, which holds the connecting rod to the piston. Make sure the wristpin slides in easily and doesn’t bind up on either the piston or the rod. With quality parts, like these items from Lunati, it’s usually not an issue.

Spiro Lock Piston 9/28

7 Finally, Greg dropped the other Spiro lock in place and the first piston/rod combo was ready. Just seven more to go and we were on our way!

Hastings 10/28

8 If you didn’t enjoy installing the locks, you’re probably not going to like the rings either, although they are very simple to install after you get used to the process. Lunati included Hastings rings in the Sledgehammer kit, which utilize matching 1⁄16-inch top and middle rings, paired with 3⁄16-inch oil control rings.

Oil Control 11/28

9 The oil control rings come ready to install and go together as a package of four individual parts. Greg installs the lower ring first, followed by the “flex vent” ring, and then the top and bottom oil control rings. Note that these all fit in the lowest ring gap.

Compression 12/28

10 Both upper compression rings (the top and middle ring) need to be file-fit to the cylinder. Out of the box, the rings have almost no gap—the distance between the ring ends, measured in inches—and need to be opened up to account for the metal’s expansion (with heat). Greg spec’d a .025-inch ring gap for this 383 build and every compression ring needed to be cut to that spec.

Manual Ring 13/28

11 Using a manual ring filer, which you can buy for less than 100 bucks, Greg got to work filing the rings to fit. Be very, very careful here…if you grind too much, you can’t ever get it back, and you’ll have to order another ring to make a full set.

File Check 14/28

12 File a little, check the gap. File a little more, check the gap. This goes on until you are happy with the measurements and then you have to do it again for 15 more rings. Pro Tip: Do the middle rings first, followed by the top rings, so that you don’t mix up the two. When you are finished fitting a ring, leave it in the bore.

Measure Cut 15/28

13 Greg found the top rings a little “quicker” to file, which meant he had to pay special attention to keep from removing too much material. This is one place where measure twice, cut once doesn’t work… Measure as many times as possible and cut in very small increments!

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