Small-Block Chevy Build - Real Cool Street Heat

We Test Some Cost-Effective Parts For Big Street Power

David Vizard May 1, 2008 0 Comment(s)
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I have often heard it said that significant things happen in threes. I'm 90 percent sure it's coincidental, but the other 10 percent-well, not so sure. It's a Monday morning and I get a call from DSS Racing's Tom Naegele. Tom wants to know if I would like to put the latest iteration of its new line of small-block Chevy pistons through some kind of torture test. "Sure," I replied. "When I have a suitable block, I will give you a call." Later in the day I don't get one, but I do get three e-mails asking if the Zex perimeter feed plate nitrous system is any good. My response? "Don't know-haven't tried it yet."

Well, later in the day I call what is rapidly becoming my favorite core supplier, AAEQ. During my conversation with AAEQ's Eric Haugland about a late-model short-block for piston testing, the subject of porting its highly successful iron EQ23 heads crops up along with-you guessed it-its use with nitrous. Bingo-we have a plan for a street nitrous-injected 350 using DSS's new pistons, a Zex nitrous kit, and a set of ported EQ23 iron heads.

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Here is our EQ-sourced block after T&L cleaned and machined it. It's painted and ready for the rotating assembly to be installed.

After talking to all parties concerned, we decided on a basic spec and targets to shoot for. First, this was to be an honest-to-goodness street motor, not something thinly disguised as such. How honest? A steady (no lope) idle of no more than 650 rpm, plus the ability to pull right off idle in high gear. It must be capable of decent mileage and have enough oomph to push a typical automatic-equipped 3,200-pound car on slicks under the 13-second barrier without the nitrous and into the 11s through the mufflers with the nitrous.

First, the heads. The results to date with the EQ23 heads have been stellar, to say the least. The heads looked like they were very porter friendly to the extent that even a first-timer could get results. From that you might mistakenly assume they must not be that good in terms of flow to start with if even a basic porting job bumps flow up significantly. Actually, it's the other way around. Because the port shape is so good, the out-of-the-box flow is hindered to a far greater extent by minor casting flaws than would be the case for a fundamentally poor port design.

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The cost-effective T&L rotating assembly included a cast steel Scat crank. We have used these without problems at the 650 lb-ft/650hp level. All our bearing clearances were determined by micrometer measurement before assembly.

As far as the cam and valvetrain are concerned, we decided to partially bias the cam spec toward serving the engine's needs when the nitrous is in operation. A cam favoring output when the nitrous is in use needs to be on a wider lobe centerline angle and be more advanced in the engine. This meant using a cam on a 110 LCA angle instead of the 108 known to be optimal for an engine of this spec but without nitrous. This cam would be installed 6 degrees advanced instead of 4. The earlier opening of the exhaust valve allows the cylinder much needed extra time to blow down before the piston reaches BDC. This extends the useful rpm range at the top end.

Along with this, the reduced overlap resulting from the wider LCA will allow the engine to idle more slowly and smoothly. That same reduction in overlap will also improve low-speed driveability about town. All the advantages of a nitrous-biased cam spec sound good, but there are some negatives in terms of reduced torque and hp while the nitrous isn't in operation. For us, a torque reduction of some 10-15 lb-ft can be expected along with about the same in top end power. When the nitrous is on, the useable high-end rpm is 300-500 more, and the power at this higher rpm is up to 30 hp more.




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