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How to Rebuild a 350 Short-Block Engine - Repurposing

We breathe new life into an old short-block with a few aftermarket parts.

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These days, recycling is all the rage. Airplanes get ground up and turned into beer cans, which eventually get melted down and formed into some other widget we just can't live without. In a way, hot rodding is one of the “greenest” hobbies out there. We take old worn-out junk and rebuild it into functioning items. This is especially true of engines. Sometimes, it's an old crank that's cleaned up and put to use again, or maybe it's a discarded engine block left to gather dust in the back of a shop. Whatever it is, the whole concept of turning trash into treasure is what drives our hobby.

The nexus for this story was an old short-block we found in the back of the shop. After doing a little sleuthing, we determined it was the remnants of a GM ZZ4 crate engine. Now, we're pretty sure that many hot rodders have half-built engines lying about, so why not see what the addition of a few aftermarket parts could recycle these mills into? In our case, the ZZ4 first hit the streets well over 10 years ago. Back then, 355 horsepower was a much more impressive number, and the price of gas was much lower. So our plan became to up the power a bit and do it so it'll run on a lower grade (less expensive!) of gasoline. We also wanted to try out a few parts that have recently caught our attention. The first was a Thumpr cam from COMP. These hydraulic roller cams are ground and profiled to maximize the rough-idling characteristics without negatively impacting the power output or streetability of the engine. In other words, the hot rod sound we love without the hassle.

We also wanted to try out Summit Racing's new line of wallet-friendly aluminum heads. The cost of cylinder heads can quickly consume the lion's share of any engine build budget, so finding some affordable choices that still make good power really helps to keep the costs down. To make sure we did it right we hauled all the parts over to EVOD Garage in Escondido, California. Oh, and if this mill looks a bit familiar it's because it powers Dick Kvamme's road trippin' '61 that graced last month's cover.


01. Our starting point is this clean ZZ4 GM Performance Parts 350-inch short-block. At some point someone swiped all the parts off of it and left it languishing in a corner. When it had all of its original parts, this GM crate engine was rated at 355 horsepower and 405 lb-ft of torque. Not bad, but we’re pretty sure we can improve upon those numbers without sacrificing street manners or breaking the bank.


02. Since it had been sitting around for who knows how many years, we decided to do a quick teardown and inspection of the short-block. We found all the GM parts, including the powdered metal rods, aluminum pistons, and forged crank, to be in great condition. Better safe than sorry and besides, it’s no fun building things twice.


03. For a camshaft, we ditched the factory 208/221-degree, 112 LSA bumpstick for a COMP Thumpr stick (PN 08-600-8, $297). The Thumpr wasn’t crazy big (227/241-degree duration, 107 LSA), but it will give the engine that lumpy hot rod sound we dig.


04. The GM timing chain was MIA so we picked up a nice COMP roller timing chain and gearset from Summit Racing (PN 3136, $72).


05. With the parts in place, we were able to properly degree the cam. This often overlooked step is crucial if the engine is going to run to its full potential.


06. The roller system used this set of GM hydraulic lifters and a spider lifter retainer.


07. We then installed a Rattler Torsional Vibration Absorber from TCI. The Rattler is designed to absorb, rather than just damp, vibrations and is SFI 18.1 certified.


08. When it came to heads, we had a choice to make. The GM heads that came with the ZZ4 engine had 58cc chambers that worked the compression to right around 10:1, which meant we needed to use 92-octane gas. Given today’s gas prices we opted to go with Summit Racing’s 200cc street/strip aluminum heads (PN 162111, $1,050 pair). These feature 64cc chambers that drop our compression to around 9.6:1, allowing us to run much less expensive 87-octane gas if we choose.


09. For $1,000, it’s really hard to beat these Summit-branded heads. They feature phosphorous, bronze valveguides; ductile iron valve seats; and came fully assembled with 2.02/1.60 stainless steel valves. The heads also had screw-in rocker studs, guideplates, and 7-degree valve locks. To secure them to the block we used a set of Fel-Pro head gaskets (PN 1003, $38 each) and a set of ARP stainless head bolts (PN 434-3601, $169). If you want to sacrifice a little bling and save a few bucks you can get the bolts in black oxide for $79.


10. For rockers, we decided to roll with a set of COMP Ultra Golds we had left over from a previous build (PN 19004-16, $282). On this engine we could have gotten away with a lesser rocker, but the Ultra Golds are rock solid and being full-roller, they will free up a bit of power. This did mean we needed to swap out the 3/8-inch rocker studs that came with the Summit heads for some 7/16-inch versions.


11. It’s a street engine, so we opted to go the dual-plane route when choosing an intake. This Weiand Speed Warrior aluminum intake (PN 8501, $225) featured long, separated runners for improved bottom and mid-range power. Plus, the runner design won’t choke off the power in the higher rpm range (up to 6,000 rpm).


12. Now, when it comes to valve cover gaskets you can cheap out and go with standard cork, but we much prefer these Fel-Pro steel-core silicone pieces (PN 1628). They seal great, which equates to no leaks—oil or vacuum. They will also last nearly forever. Trust us; they are well worth the $50.


13. To spark the fuel we chose a ready-to-run MSD billet distributor (PN 8360, $290). With a vacuum advance we will get better economy, which is even more important these days. The housing features an all-billet 6061-T6 aluminum design for super accuracy and an oversized steel shaft that is QPQ-coated for low friction. Sealed bearings at the top and bottom of the distributor make sure it all stays steady, which equates to accurate spark delivery at any rpm.


14. This engine belongs to Dick Kvamme over at Best of Show Coach Works and since they’re always willing to lend us a lift or spray a little paint, we asked the guys over at Eddie Motorsports (EMS) to whip up some special valve covers for the small-block. EMS can laser etch any design you send them onto their valve covers, air cleaners, breathers, or other widgets for a fee based on the complexity of the design. Pricing starts at $40, and the logo we sent them ran about $50 for the pair, plus the cost of the valve covers.


15. To top off our engine, we went with Holley’s new Ultra Street Avenger carburetor (PN 86770HB, $599). At 770 cfm, it’s sized just right for our mill and the electronic choke will make it easy to live with on the street. The carb features ultra-lightweight aluminum construction along with billet metering blocks and base for more strength than cast pieces. It’s also easy to adjust and change the spring for the vacuum actuated secondaries.


16. At Westech Performance, we strapped the newly revitalized ZZ4 engine to the Superflow dyno, filled the tank with 87-octane pump gas, and fired it up. Once properly broken in, Westech’s carb-guru Steve Brule started making pulls and performing adjustments. Over the course of a dozen pulls, he slowly added timing, installed a lighter spring for the vacuum secondaries, and swapped the jets around. On pull 13, we were rewarded with our best corrected numbers of 413 hp and 415 lb-ft of torque. That’s more power than the ZZ4 made stock and we did it with less compression and on lower octane gas that GM recommends. As for torque, the peak isn’t much higher than the ZZ4’s advertised number, but we really like the flat curve and that it made over 370 lb-ft way down at 3,000 rpm. If we didn’t mind upping the compression and running the more expensive swill there was even more power to be had, but we still remember when a 400hp engine was enough to make us smile. Besides, this is more than enough to motivate Dick Kva


TCI Automotive
Ashland, MS 38603
Summit Racing
Akron, OH
Westech Performance
Mira Loma, CA 91752
Eddie Motorsports
Rancho Cucamonga, CA 91730
Holley Performance Products
Bowling Green, KY 42101
Westminster, CA 92683
Evod Garage
Competition Cams
MSD Ignition



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