The Chevrolet Tri-power carburetor system—made famous under the hood of hot models such as the big-block-powered L71 and L89 Corvettes—is, to us, one of the best looking ones of all time. Well, the folks over at Holley have come up with a system that lets you have the same deal on your small-block Chevy. With the Holley Tri-Power system you can cruise and the center 2bbl carb sips fuel, or mash the gas and let all three carbs—over 1,000 glorious cfm—gulp atmosphere. It’s the best of both worlds: economy and performance (if you can keep your foot out of the throttle).
The real question we had was whether the good looks would be at the cost of performance. After all, we’ve build a lot of small-blocks over the years and it’s hard to beat a properly sized carburetor on a single-plane intake in terms of top-end horsepower. So, to see how the Holley Tri-Power would do, we decided to build one of the most popular small-blocks out there, a 383 stroker. Our plan was to build it stout with free-flowing Air Flow Research (AFR) Eliminator heads and a 10.75:1 compression ratio, but keep it on pump gas and easy to live with on the street. Follow along as we wrench together a retro-looking mill using a slew of modern performance parts. But don’t call it a six-pack … unless you’re a Mopar fan, in which case you might have made a wrong turn someplace.
01. The starting point for any engine is the block. But the big problem with building a Gen I small-block-based engine is finding a decent core. In the past we’ve had to buy three or four used engines before ending up with one that wasn’t already bored to the max, cracked, rusted, or otherwise unusable. This is where Summit Racing comes in. They sell worked-over, used blocks that have been cleaned up and ran through a machine shop. The one we chose (PN SUM-150100-30) was a one-piece-rear-main block with the cam bearings already in place.
02. The block came pre-punched to 4.030 inches on the bores and was a four-bolt main version. We found our Eagle I-beams just barely hit and required a small amount of grinding. These 1996-’00 blocks work with hydraulic roller or hydraulic flat tappet cams and will accept a mechanical fuel pump. For the mains we used the Clevite bearings included with our rotating assembly.
03. We wanted strong power and decent street manners so, after consulting with Steve Brule over at Westech Performance, we came up with Comp hydraulic roller stick (PN 12-000-9) that measured out at 234/240-degrees duration (at 0.050-inch) and with a lift of 0.543/0.540-inches (installed at a 105 intake centerline). The lobe separation angle (LSA) spec’d out at 109 degrees. Since it’s a custom cam, the grind number is CS 13082s/13142s HR109.0. Once lubed up, Evod’s Chris Pollock slid it into place.
04. The internally balanced rotating kit (PN 10508) was sourced from Eagle Specialty Products and included their 3.75-inch stroke 4340 steel crank. Made from a non-twist forging, these cranks are fully heat-treated and stress-relieved. In addition to shot-peening and nitriding, they are magnafluxed as well as sonic tested. Lastly, each journal is micropolished.
05. Included in the Eagle kit was a full set of Mahle PowerPak forged aluminum pistons (PN SBC425030F05). The flat-tops featured two valve reliefs and a compression distance of 1.425-inch. Each piston was hand deburred by Mahle and then coated with a dry phosphate to protect against ring micro-welding and pin galling. The skirts have Mahle’s proprietary Grafal antifriction coating and the set came with low-drag rings, steel pins, and wire locks. The +5.00cc piston contributed to our targeted 10.75:1 compression ratio.
06. The kit also came with Eagle’s recently introduced 4340 forged steel 5.7-inch FSI I-beam connecting rods. These are a great high-strength, low-cost alternative to their H-beam rods and came equipped with 7/16-inch ARP 8740 bolts and silicon-bronze bushings. They are good up to 750 hp in a small-block application, so they are more than enough for our 383. They can be ordered shaved for extra stroker clearance.
07. After mating all the pistons with their respective rods Chris file-fit the rings and popped the assemblies into the bores using our Summit Racing 4.030-inch installation sleeve.
08. The mains were torqued to 68 ft-lb for the inner bolts and 65 ft-lb for the outer bolts, while the rod bolts were taken to 68 ft-lb in three passes, just like the mains.
09. To keep the timing right, we installed a Comp keyway-adjustable billet timing set (PN 7100). The induction-hardened steel gears and double-roller arrangement will provide durability while the nine-keyway crank sprocket allows for a maximum of 8 degrees (advance or retard) adjustability. The kit also included a Torrington roller thrust bearing.
10. When we ordered the custom-grind cam we neglected to note that it was for a later, roller-ready block. As such, we needed to run a Comp cam button (PN 200) instead of a cam plate. Lesson learned, but it was an easy fix. The sprocket was secured by three ARP cam bolts (PN 300-1001). Cam thrust was set to 0.006-inch.
11. Chris then degreed the cam. He was able to lock down 104.5, which was the closest he could get to the recommended number using the keyways on the sprocket.
12. The difference between an average engine builder and a good one all comes down to the details. We like working with Chris since he measures and double-checks everything. Here you can see the benefits of a stainless workbench for keeping notes during the build.
13. The block came decked, but as we mentioned Chris it pretty picky so he had his machine shop take a hair off to get the pistons right where he wanted them: 0.001-inch in the hole.
14. Heads can make or break an engine’s power output so it’s the right place to spend cash. Air Flow Research (AFR) is known for crafting no-compromise heads so we ordered a set of their 195cc SBC Eliminator competition heads (PN 1095-716). They came fully CNC-machined (combustion chamber, intake, and exhaust ports) and are known for being solid performers. Chris double-checked the combustion chamber volume and found it to be 63.2 cc. The valves were 2.080 on the intake side and 1.600-inch for the exhaust. Designed with a 23-degree valve angle the A356 aluminum heads offer exceptional flow and work great on engines up to 400 inches that rev up to 6,500 rpm.
15. After sandwiching a Fel-Pro gasket (PN 1033) between the Summit block and AFR head, Chris secured it in place (70 ft-lb) with fasteners from our ARP bolt kit (PN134-3701). If head studs are more your style, the ARP part number is 234-4301.
16. To make power we needed rpm, so the hydraulic lifters weren’t a place where we wanted to skimp. These Comp short-travel race hydraulic roller lifters (PN 15853-16) have link bars and are perfect for later roller or earlier flat tappet blocks. The short travel design limits the lifter’s internal piston as it’s pumped up. By doing this, the lifters cut down on the loss of power and limit valvetrain issues at higher rpm. The lifters came REM-finished and black oxide coated for increased durability.
17. With the heads in place we could go ahead and install the ARP 7/16-inch rocker studs and guideplates that came with the heads. Chris did the math and figured that we needed a set of Comp 7.150-inch hardened pushrods.
18. Finishing out our valvetrain was a full set of Comp Ultra Gold 1.5:1 ratio aluminum rocker arms (PN 19004-16). These CNC-machined roller rockers stand up to hard use and utilize polylock nuts to make sure they stay properly adjusted.
19. After flipping the long-block over, we installed the Summit oil pump. This high-volume pump came in the oil pan kit (PN SUM-PANKIT8) and was mated to the proper steel pickup for the pan. The kit also included the necessary gaskets and pump driveshaft. We added in an ARP oil pump stud kit.
20. Normally when we rebuild engines this rear main bearing housing is just cleaned up and reused. But our new block didn’t have one and it took a bit of work to find a stock-style one to buy. This one was found on eBay and set us back $24 shipped.
21. The black, zinc-coated Summit Racing Pro Pack steel oil pan holds 6 quarts and has an integrated scraper and windage tray (individual part number of SUM-G3603). It’s good for strokes up to 3.875 inches and was installed using the included cellulose/nitrile rubber Summit oil pan gasket and some of the stainless six-point ARP bolts from the master engine accessory package (PN 534-9601). You can also spot the TCI Rattler damper that we installed with an ARP crank bolt.
22. The whole point of this build was to try out Holley’s new Tri-Power intake system. We’ve done 383 small-block engine builds before, but those were with a tried-and-true single-carb setup. The Tri-Power deal certainly looked cool but we were curious if it would perform as well as it looked. The kit (PN 300-521) included a medium-rise 3x2 Weiand intake manifold, three Holley 2-bbl carbs (two 325-cfm outboard carbs and one 350-cfm center carb with electric choke), fuel lines, progressive throttle linkage, along with reusable retro-styled air filters.
23. We went with the dichromate finish since we like the old-school vibe, but they are also available in a shiny silver finish (PN 300-522). The kit ships from Holley disassembled. Here it is fully assembled and sitting atop our stroker long-block.
24. To provide spark we opted for a PerTronix Flame-Thrower billet distributor with the Ignitor III upgrade. This plug-and-play distributor features cobalt magnets and a Hall effect trigger for stable timing along with their Ignitor III adaptive dwell module. The adaptive dwell maintains peak energy throughout the entire rpm range, which reduces misfires. It also puts out five times more spark compared to points and senses startup to develop more energy for faster starts. Lastly, it has a built-in, user adjustable rev limiter.
25. With the engine all buttoned up we hauled it over to Westech Performance for some pulls on their SuperFlow dyno. The engine was filled with 6 quarts of Lucas break-in oil and was running pump gas supplied by Rockett. We had planned on running Holley’s finned retro-styled valve covers but we ordered the ones without breather holes so we had to toss on a set of shop valve covers. Not as pretty, but functional enough for our testing.
26. After a few pulls, the numbers were looking really good, but Steve Brule thought changing the jets on the middle 2-bbl carb would help a bit, so we went to 62 on the primary. To do this we had to pull the front carb, but the jet swap was the same as any other Holley. Timing was set to 36 degrees.
27. To be honest, we weren’t sure what to expect and were thinking the power numbers would be in the 470 range. Well, after the jet change we had a best pull of 498 hp at 5,900 rpm! And the nice part is that the power held steady past 6,200 rpm. Of course, the AFR heads helped tremendously, but the intake didn’t seem to cost us performance. The real surprise was the torque curve, even more than the peak torque number of 491 lb-ft at 4,300 rpm. When we rolled in at 3,000 the engine was already spitting out 441 lb-ft and even at 5,900 rpm (peak power) it was still making almost 450 lb-ft. That’s a very long, flat curve that makes a street car fun to drive