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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
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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!

Install Rotating 16/28

14 With the ring work complete (it took a while), Greg was finally ready to flip the block over and begin working on the actual installation of the rotating assembly. The Sledgehammer kit shipped to us with a set of King Allecular chamfered main bearings, which simply dropped into the upper half of the mains.

Lunati 17/28

15 The 3.750-inch Lunati crankshaft dropped right in place and fit perfectly. Note that our engine block features a one-piece rear main seal, which required us to order a matching one-piece main crankshaft. Lunati stocks both cranks, so let them know what you need when you order.

Arp Small Block Fastener 18/28

16 As usual, we didn’t have any plans to use stock or no-name fasteners in our build and ARP stepped up big, sending us a complete small-block fastener kit that shipped with almost every single bolt, stud, nut, washer, and lube that we would need for the entire engine. The four-bolt main stud kit went in first, using ARP assembly lube to get everything snugged in place.

Electric Impact 19/28

17 The stock four-bolt main caps dropped in place next, which are clamped down tight with a set of traditional six-point nuts and the supplied flat washers. Greg installed the studs first, and then used an electric impact to get the nuts in place. Finally, they were torqued to spec, and we were ready to move on.

Connecting 20/28

18 All quality connecting rods will ship to your door assembled, but you or your builder will have to take them apart to get them wrapped around the crankshaft. It’s not quite as simple as just removing the two bolts, so take your time breaking the cap from the lower portion of the connecting rod.

Ring Compressor Cylinder 21/28

19 With the connecting rods apart, Greg used a 4.030-inch ring compressor to snug the rings down and then placed the entire assembly into the cylinder bore. With a couple of taps from a wooden (or plastic mallet), the connecting rod and piston slid into the bore.

Connecting Rod 22/28

20 Both sides of the connecting rod require a bearing (if you did not know this, we recommend you outsource the majority of your engine build), which is installed into the big end of the rod by simply sliding them in place. Note the notched portion of the bearing, which mates to the cap for a perfect fit.

12 Point Arp Connecting Rod 23/28

21a Once the connecting rod was around the crankshaft, Greg slid the cap and bearing over the crank and installed the 12-point ARP connecting rod bolt.

12 Point Arp Connecting Rod Bolt 24/28

21b Seven more holes to fill, seven more pistons and connecting rods to install. Once you get one, the rest just seem to fall in place.

Stroker 25/28

22 Remember the “stroker clearancing” the machine shop performed? Here you can see exactly what that is for. Without machining the block, the connecting rod bolts would actually hit the block, which would make for an interesting initial startup. Always double check to ensure proper clearance…we had plenty!

Camshaft Install 26/28

23 Comp Cams cut us a nice 230/236 duration at .050-inch hydraulic roller camshaft that was designed for a “strong mid-range and top end.” With .576/.570-inches of lift and a 113-degree LSA, this camshaft should work really well in a 383 application and make great power on the street or track. Installing it was as simple as lubing it up and sliding it in place.

Thrust 27/28

24 With the camshaft in place, Greg installed the thrust plate and dropped the Hi-Tech Roller Race timing set in place. Thanks to the keyway crank sprocket, this is an adjustable timing set, although we chose to install the camshaft “straight up” (dot-to-dot) for our initial build.

Sledgehammer 383 28/28

25 And just like that, our Sledgehammer 383 bottom-end build was complete. Next time we’ll drop a set of cylinder heads in place, along with the complete valvetrain, and AntiVenom will finally button up the engine before installing it in our TPI-equipped Formula. Stay tuned, this 383 is going to fly!


Automotive Racing Products
Ventura , CA 93003
Seffner, FL 33584
Competition Cams



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