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Still a Float: SBC Stroker Spring Upgrade

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By Richard Holdener/Photos By Author

Spring had sprung on our stroker, so it was time for an upgrade!

Sometimes performance upgrades come from desire, while others out of sheer necessity. Unfortunately for us, this valve-float (actually control) test was the latter. It is often said that the whole is more important than the sum of its parts, and this is certainly true when it comes to the internal combustion engine. Think about running a performance motor without just one component missing, like a crankshaft, camshaft or cylinder heads.

The results would be predictable, it simply wouldn’t run. Even the minor components can create havoc, like a single pushrod, rocker arm, or in our case, a valve spring. Missing just one of the literally hundreds of components that make up the motor can severely handicap the combination, to say nothing of potentially ruining a very important dyno session. But as they say, that which does not kill you, makes you stronger, so follow along as we take you through our broken valve-spring adventure.      

The adventure started with the attempted dyno session of a 383 stroker Chevy supplied by BluePrint Engines. The motor had already seen plenty of dyno use, with everything from nitrous to superchargers, including boosted testing run on E85. We are not sure if it was abuse, metallurgy or just plain bad luck that caused the spring to fail, we just know that the 383 stroker was, shall we say, reluctant to rev.

Before we get to the fix, know that the stroker had run endless dyno sessions with the afore-mentioned boost and nitrous. The reason for all the boost and nitrous was that this crate motor was designed from the get go for power adder use. The stroker featured all the good stuff, including forged internals, aluminum heads and a healthy cam profile. The low compression also made the motor boost and nitrous friendly, but after many sessions, one of the exhaust springs finally gave up the ghost. 

Swapping out the springs was a simple procedure, though we employed several specialty tools, including a spring compressor, a spring and installed-height tester. Before attempting to remove the spring with the compressor, we made sure to give the retainer a good whack with a hammer to dislodge the keepers from the retainer. Prior to compressing the valve spring, we supplied air pressure to the cylinder through the spark plug hole using a leak-down tester.

After the spring compressor was secured to the rocker stud using one of the poly locks, we were able compress the spring and remove the keepers using the magnet. We then unbolted the poly lock and removed the broker dual-spring assembly. As luck would have it, the boys from Westech had a set of 26056 dual springs from Comp Cams on hand that fit perfectly on our stroker. Not only were they the correct installed height for our set up, but they also fit our retainers and spring cups and were sizable step up in spring rate, something this combination desperately needed (especially under boost).

 If you check out the supplied graph, you can see just how much a single damaged valve spring was worth. The motor experienced severe valve control issues, which had a negative effect on both power production and rpm capability. Remember we said that just one component can ruin an otherwise good combination? This valve spring was a perfect example, though we did upgrade ALL of the valve springs in addition to simply repairing the single damaged unit.

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The upshot of our spring upgrade was one very happy stroker motor. Because of the diminished rpm potential, the 383 stroker produced just 431 hp and 451 lb-ft of torque with the damaged spring. After installation of the new valve springs from Comp Cams, the power output jumped to 453 hp and 457 lb-ft of torque, but the major difference was rpm potential. No longer did the power curve randomly flutter, then give up completely at 5,400 rpm. Instead, the stroker now pulled strongly to 6,500 rpm, and (every bit as important) was now ready for even more boost and nitrous.        

Blueprint 383 Spring Test-Comp Upgrade vs Broken Spring
Things really go all to hell when you break a valve spring! Just check out how unhappy the stroker motor was with a broken (exhaust) spring. The motor wouldn’t rev, it wouldn’t make any power and it was basically just one big, hot mess. The second curve is what a 383 should look like when things go right! The new springs allowed the stroker to rev cleanly up to 6,500 rpm, and reach the power potential of the combination. With over 450 hp and 450 lb-ft of torque, the 383 was just begging for some boost, or maybe even a big shot of Zex nitrous (or both)!

Sources: BluePrint Engines, Comp Cams