Chevy Corvette 350 Engine - One-Stop Topping

With Help From TFS, We Make 428HP From An Old 350-And It's 87-Octane Friendly.

Dan Ryder Nov 1, 2008 0 Comment(s)
Sucp_0811_01_z Chevy_corvette_350_engine Finished_350_engine 1/29

While many car-crazed enthusiasts enjoy spending time researching the options necessary to create the ultimate engine combination, some of us don't have the time-or we don't know how. Fortunately for us, there are top-notch manufacturers such as Trick Flow Specialties in Tallmadge, Ohio, that can ease the pain with a complete line of top-halfengine packages. Each package is available in a range of horsepower ratings, depending on your habits and what you want to achieve.

After a brief search, we found a suitable short-block to perform the installation and testing of the TFS 445-horsepower package. As many of you recall, we performed a three-part installment titled "Shoestring Stroker," written by Chris Werner, which was a 383-inch mouse motor built for Editor Jim Campisano's '72 LT1 Corvette (Project Homewrecker).

Sucp_0811_05_z Chevy_corvette_350_engine Exhaust_manifold_removal 2/29

After yanking the crusty old 75,000-mile passenger car 350 from the Vette, it was set in the corner like a child in detention. Editor Campisano and I figured the reliable 350 would be a great candidate for the swap because they're readily available and were found in many Chevrolets over the years. This particular unit was originally from a 1973 passenger car, which was ultra low in the compression department (8.0:1), thus allowing for emission compliance and the use of 87-octane unleaded fuel.

Sucp_0811_04_z Chevy_corvette_350_engine 350_small_block 3/29

Here is the 350-cid small-block that was lifted from Editor Campisano's Corvette. After running the numbers, we narrowed the engine down to a 1973 passenger car 350 with about 175 hp and an 8.0:1 compression ratio (net rating including draw for added accessories. Actual gross horsepower was probably in the neighborhood of 210). For starters we have to remove these old Vette exhaust manifolds.

The Trick Flow top-end package includes the TFS 195cc 23-degree aluminum cylinder heads, a roller camshaft with .558/.558-inch lift, ARP cylinder head bolts, guide plates, rocker studs, 1.5-ratio roller rockers, a complete timing chain and gear set, a complete SBC gasket set and pushrod length checker.

Since our engine was originally equipped with a flat tappet camshaft, we ordered Trick Flow's new tie-bar roller lifters for our project. Considering the array of engines to which this kit will adapt, you must measure for pushrod length once the cylinder head, lifter and camshaft are installed onto the engine.

In order to properly distribute fuel to the engine, we called upon Edelbrock in Torrance, California. TFS suggested the use of an Edelbrock RPM Air Gap intake manifold (PN7501) designed for '55-'86 262-400 cid Chevy V-8's. The air-gap design features open air space keeping the runners separate from the hot engine oil, resulting in a cooler, denser charge into the engine, hence creating power. The RPM Air Gap is recommended for use in the 1,500-6,500 rpm operating range.

Next we removed the valve covers and loosened off all of the rocker arms, leaving the valves closed for a cylinder leak-down test. The cylinder leak-down will give us a general idea on the condition of the engine, and whether it has any substantial leakage through either the valves or the rings. Surprisingly, our 350 test mule performed very well, with the highest percentage of leak-down coming in at around 12 percent, which is normal for an older unit with some miles on it.

Sucp_0811_19_z Chevy_corvette_350_engine Timing_chain 7/29

Supplying fuel to the Edelbrock intake will be a Speed Demon 750-cfm carburetor from Demon Carburetion/Barry Grant. The Speed Demon line is offered with either vacuum secondaries and an electric choke, or with mechanical secondary designs; we used the latter. The Speed Demon is also offered in a wide range of sizes from 575 cfm to 850 cfm. We're utilizing the Speed Demon for its reliability, drivability and power-making capabilities.



Sucp_0811_20_z Chevy_corvette_350_engine Torrington_thrust_bearing 8/29

Next we readied the TFS timing chain for installation, which contains a Torrington thrust bearing in order to control movement and reduce drag. Once installed, a cam button is employed to keep the roller camshaft from walking forward during operation.

To add a little fire, we called upon ProForm in Roseville, Michigan, for an affordable ignition set-up. ProForm suggested one of its Chevy HEI Racing Distributors, which is all new and comes complete-ready for installation. The distributor additionally includes a 50,000-volt spark through 7,500 rpm, a high-performance timing curve and a premium cap with brass terminals. ProForm also suggested that we use its Street Performance Chrome Kit including valve covers, timing cover, air filter and housing, breather, hold downs and wing nuts all in one complete kit. While the chrome kit won't supply us any additional power, it'll have us looking good!

Once our mill was complete, we went over to see Bob Oster at B&B Performance Machine in Rahway, New Jersey. Our low-compression 350 fired right up, ran like a champ and made great power.

After removal of the intake manifold we were impressed with the cleanliness of the engine. We removed the cylinder heads, exposing the low-compression pistons used back in 1973. Compression on these engines generally checked in around 8.0:1-not the most suitable when trying to make horsepower, but we like a challenge.

Our next mission was to remove the harmonic damper to gain access to the timing cover. After removal of the balancer and timing cover, we discovered the timing chain was in decent shape, despite having a lot of slack.

We enlisted a magnet to remove the lifters from their bores and then removed the camshaft carefully, not wanting to hurt any cam bearings (don't forget to pull the mechanical fuel pump if so equipped). Wow, take a look at that lifter, it's shot, and this engine was on borrowed time. The worn cam lobes also indicated that this engine would not have endured many more miles. Here's the new TFS piece being installed into the block. The TFS unit contains a lift of .558/.558 and a duration of 246/254. This thing is really going to breathe!

Sucp_0811_21_z Chevy_corvette_350_engine Timing_cover 15/29

As we tried to install the ProForm timing cover, a problem was encountered. The design of the cover was not compliant for use with a roller camshaft utilizing a cam button (something to keep in mind). It was then time to pull the stock unit from the pile of old parts and clean it up for use. Sometimes functionality takes precedence over looks. We laid the cylinder head gaskets on our previously cleaned block surface. All gaskets are included with the TFS package.

All rockers were properly adjusted as per the instructions and the Edelbrock RPM Air-Gap intake manifold was installed. The Edelbrock unit is a dual-plane design and will offer a better idle quality, as well as low-end grunt compared to a single plane unit. While a single-plane unit might have given us a better horsepower number, we're looking for the total package.

Now came time to lay the 195cc TFS 23-degree cylinder heads atop our assembled short-block. These TFS heads come with 64cc chambers. The valves measure 2.02-inches (intake) and 1.60 (exhaust). Included in the package is a set of ARP cylinder head bolts, known for their reliability and strength. We torqued the bolts according to the sequence provided by TFS in three stages: 32 lb-ft, 52 lb-ft and 70 lb-ft.

The TFS package comes with a complete set of instructions, including torque specifications and patterns. Once the cylinder heads were torqued, we installed the newly designed TFS hydraulic tie-bar style lifters (not included). A tie-bar style lifter is necessary because older engine blocks didn't have provisions for a roller type camshaft. The TFS units fit perfectly with no binding.

It's time to install the guide plates and rocker studs to the cylinder heads. We measured for proper pushrod length, using the length tester in the kit. The stock pushrod (7.750-inches) was used on the valve stem to the right and the new TFS hardened piece (7.250-inches) on the left. As you can see, the pattern on the left shows the rocker tip riding within the middle portion of the valve stem tip, and the valve stem tip on the right, toward the bottom. Always check this by temporarily installing a pushrod length checker, along with the rocker, and rotating the engine one revolution. Adjust the length checker as needed to seat the rocker fulcrum toward the middle of the stem. Finally we installed the CNC-machined TFS 1.5 ratio roller rockers to actuate the valves in a controlled manner (pushrods not included).

Next we bolted down these awesome-looking valve covers from ProForm and topped off the Edelbrock intake with the Barry Grant Speed Demon 750 carburetor. The Speed Demon will offer excellent drivability, idling characteristics and most of all - power!

Finally we installed the ProForm HEI race distributor (PN66941R), which comes complete and ready to use, providing 50,000-volt spark through 7,500 rpm. Now for the moment of truth. We packed up and headed over to B&B Performance Machine in Rahway, NJ, to get the digits on our revamped 350.

Sucp_0811_38_z Chevy_corvette_350_engine Dyno_chart 28/29

TFS ProCharged kit
Once the mouse was mated to the SuperFlow engine dyno, it fired right up with 40 psi of oil pressure and sounded mean. After a few jet changes to the carburetor (we settled on 77 primaries and 84 secondaries), and multiple timing adjustments (37 total worked best), the numbers were in. TFS rated its kit at 445 hp and 40 5 lb-ft of torque. We squeezed out 428.4 hp and 421.4 lb-ft of torque-a little shy on horsepower, but way up on the torque side. Remember, we're using an old, low-compression, smog-compliant short-block, which after being topped with the TFS package checked in at a still low compression of approximately 9.0:1. TFS recommends a minimum compression of 9.5-10:1.

Now that's impressive, and adding a flat-top piston to the equation alone will net us well over 450 horse! We took a worn 350 short-block equipped from the factory with low compression, threw a total of around $2,500 worth of quality components at it, and gained 253 hp over the stock rating. That's about ten bucks per horsepower. And we ended up with a serious street/strip slayer that can run on 87-octane gas all day long!

Sources

Trick Flow Specialties
Tallmadge, OH 44278
330-630-1555
www.trickflow.com
Summit Racing
Akron, OH
800-230-3030
SummitRacing.com
B&B PERFORMANCE MACHINE
Rahway, NJ 07065
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