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The following are dyno tests of the popular Small Block stroker engines. These engines are essentially the same, depending which block was used. Due to its larger stock bore, the 340 block yields about 6 more cubic inches than the stroked 360.
The block had our usual preparation which, among other things, includes Magna-fluxed, block, ultra-sonic tested to determine cylinder wall thickness, line honed, square decked. Bored and honed with a deck plate and our modified oil system .Proper decking gave us an ideal 0.035"/0.040" quench height so we don't have to run a bunch of total timing, anything over 30 degrees is damaging and power robbing.The first test was a 360 block with the 4" stroke (360/408) that was built to be what we call a "stealth" build-up. In other words it was to look like a stock 360 engine (1978 Lil' Red Express truck) on the out side, but be well modified on the inside. It used the original 1978 block, heads, cast iron intake and exhaust manifolds, oil pan, distributor, and air cleaner. The inside of the engine was far from stock condition. We modified everything in an effort to get as much out of the limited breathing capacity of the OEM intake and exhaust systems as possible. Starting at the bottom and working up: The crank kit was our #408K-Street. This kit features KB pistons, Eagle rods, and the 4" stroke Mopar crank, it is internally balanced and will yield a nice pump gas 9.4:1 compression with a 65cc head. The KB pistons have a quench dome which works perfectly with the stock open chamber heads. We did not use the original '051 heads; we substituted a better set of '596's. They were ported to our Stage II HP specs and flowed about 296 CFM at 0.600" lift on our bench. The valves were our 2.02" #1006; we now use the 2.05" #1007 for improved flow curves. The exhaust was our 1.625" p/n 1014; both valves had 11/32" stems. The camshaft was an earlier version of what is now our HUG HEH3742AL grind with our 1.6:1 aluminum roller rockers new. The springs are our double spring and our HUG 1202 retainers and HUG 1322 locks. The pushrods were custom length based on HUG 5479 . The lifters HUG 5003 and our premium timing chain assembly HUG 6442 with the 7 key-way crank sprocket.  The photo to the right shows the engine ready for the first dyno pulls, before the carb switch. |
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| The stock iron intake was deep port matched and had some plenum work. The exhaust manifolds (they are ugly) are stock with 2 " exhaust pipes. Whenever we do stealth engines we get questions about extrude honing the exhaust manifolds. For about $500.00 you may get 6 to 8 horsepower, I think your money could be better spent, on coatings for example. We originally tried an owner supplied and re-worked Thermo-quad carb as shown in the photos. This carb was a problem early on (the engine would not start) and we switched to a shop carb, a 750 Edelbrock that has seen many dyno tests and is a reliable piece. A good Thermo-quad could be worth a little more power, maybe! See Test #1 below. We have included a volumetric efficiency column with this test. Some of you may not be familiar with this chart. The chart lists in percentage how efficient the engine is breathing, among other things. In this test the percentage is not too good as we are accustom to seeing numbers much closer to 100% or greater. Why? Why indeed! We are doing it to make a point. As noted previously we had tried to disguise this "stealth" engine as a stocker, hence we had to use the original 1978 truck type manifolds. |
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Results: 409.2 HP @ 5400RPM and 429.7 ft-lbs torque @ 4200RPM Click here for larger image  |
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In Test 2 we switched to a pair of TTI, stepped headers, 1 5/8"/ 1 ". To say the difference is amazing is a gross understatement! Check the header photos below. The power was up 42 hp and torque up 85 ft-lb at only 2600 RPM. And the improvements just kept coming with a maximum improvement for the horsepower at 4900 RPM with 66HP more and the torque was up 72 ft-lb at 4800 RPM, WOW! Note that the volumetric efficiency is up only 6 to 10% but look at what a difference just that little bit made in horsepower and torque. The engine was breathing much better. In all honesty any headers would have helped this engine, even the dreaded "shortys", but I doubt any others would have shown as much improvement as the TTI's. When you contact TTI to order, tell Stan that we sent you! |
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This next test, #4 was a change to headers. These were the dyno headers (like oval track) that were stepped 1 5/8" to 1 ". Notice how the volumetric efficiency jumped up and the power came right along with it. |
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Results: 478.0 HP @ 5700RPM and 506.6 ft-lbs torque @ 4100RPM Click here for larger image  
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