Small-Block Chevy Engine - Danger Mouse Recap

There was a time not that long ago, when engine dynos were considered a black art. Not everyone believed what the dyno had to offer and some felt dynos were nothing more than hocus-pocus. Aren't you glad we don't live in those dark ages? Dynos are everywhere now and the reality of dyno racing has become an art form of its own. We thought it was about time to have our own dyno mule so to test any and every part imaginable just to see what would happen. So we built a 355cid Chevy and crowned it Danger Mouse (DM), in reference to the fact that it will be risking its life just to test any hair-brained idea we might come up with.

FROM THE BEGINNING
From the outset we knew DM would see a lot of abuse and we've logged close to 2,000 full-throttle dyno pulls, along with countless, unmeasured others, all without major breakage. Such reliability can be only attributed to one cause, the best parts. When building DM we stressed selection of the highest quality components to ensure a very long dyno life. The World Products 4-bolt Motown block and complete forged rotating assembly from Lunati have performed flawlessly, helping DM produce consistent results month after month after month, and we thank them for it.

Basically what we've learned in over 2 years of back-to-back testing is how to get a street small-block to produce anywhere from 300 to 700hp. All of it on pump gas, on a real world budget, and all with easy to find, off the shelf parts.

DYNO TESTS
Since no dyno test would be worth diddly without baseline power figures to compare to, the first test for DM found it equipped with the barest of bone-stock top end parts. A pair of reconditioned iron "Camel hump" heads (casting No. 461) from Powerhouse Engine Components breathed through a cast iron GM intake fueled by a professionally rebuilt Q-jet from the Carb Shop. After we felt we had a reliable stock baseline (Test 1) to compare figures to, we dove head-first into testing all sorts of cams, cylinder heads, carbs, rocker arms, spacers, headers, superchargers, EFI systems, and intake manifolds, because that's what we felt most of you would like to see. We've learned a lot from these tests and are sure we'll learn plenty more.

Note: You'll notice that some test numbers are missing from this story. With 36 documented dyno tests completed so far, we feel that the results of some of them just aren't worth taking up the limited space we have here, so we're leaving them out. Don't worry, the results in those tests were pretty boring anyways. Also, to keep testing accurate and the results repeatable, other than the parts listed, nothing else was changed and none of the parts were ever modified for each test

Test 1-Baseline:
Max 395 tq, 308 hp
Avg 376 tq, 266 hp
9.4:1 cr, No. 461 "Camel Hump" heads, COMP Cams 246PE cam (246/263 adv duration, 203/212 duration @ .050, .429/.438 valve lift, 110 Lobe separation), GM iron intake, Carb Shop Q-Jet, Proform HEI, Champion No.14 plugs, 91 octane, 37 degrees advance, 1 5/8-inch headers, 3-inch mufflers. This represents what a typical 355 cid small-block would make if it had just been blueprinted, but still used most of its stock components.

Test 2-New intake manifold:
Max 394 tq, 325 hp
Avg 380 tq, 270 hp
Installed a Weiand dual-plane intake manifold (PN 8004) and leaned out the Q-jet a bit. This netted us a 17hp gain.

Test 3-Roller-tip rockers:
Max 404 tq, 342 hp
Avg 390 tq, 278 hp
Replaced the stock stamped-steel rocker arms with COMP Cams Magnum 1.5:1 roller tip rockers, which gave us another substantial increase in power, raising peak hp by 17 and peak torque by 10. This pushed max tq over the 400 mark for the first time. Average hp and tq also improved over the stock baseline by a factor of 12 and 14 respectively.

Test 4-Retard cam:
Max 405 tq, 349 hp
Avg 390 tq, 278 hp
Retarded the cam 2 degrees, which added a little more peak power while averages stayed equal.

The next series of tests went a little deeper into the bolt-on field, but still kept swaps fairly simple. We made some improvements in torque this time, but horsepower gains were not that impressive.

Test 5-1 ?-inch headers:
Max 407 tq, 351 hp
Avg 388 tq, 287 hp
We installed larger 1-? Hooker headers. Compare tests 4 and 5 and you'll see that average torque was down by 2 lb-ft, but peak toque & horsepower were up slightly and average horsepower increased by 9. That's a fair trade to us.

Test 6-Full-roller rockers:
Max 407 tq, 351 hp
Avg 389 tq, 288 hp
Swapped COMP Cams 1.5:1 full roller aluminum rocker arms. Peak and average power increased by 1 each and we got 5 more lb-ft of torque at 3,200 rpm.

Test 7-XE256H cam:
Max 413 tq, 357 hp
Avg 396 tq, 293 hp
Swapped COMP Cams XE256H cam (256/268 adv duration, 212/218 duration @ .050, .447/.454 valve lift, 110 lobe separation) 2-degrees advanced and were rewarded with lots more grunt.

While the Q-jet carb had been working ok until now, we wanted to test a Speed Demon carb on a new Edelbrock Performer RPM "Air Gap" manifold. We also bumped up to the next size larger COMP Cams Xtreme Energy camshaft. The final reward was a new max 386 hp and 438 lb-ft of torque with new averages at 316hp/416tq. So now, we had this stock iron-headed 355 Mouse making almost 390hp and 440 lb-ft of torque! This was definitely the best power formula with the stock heads, particularly since the motor didn't respond very well to the bigger XE262H cam in Test 12. We took that as a sign that we had just about maxed out the stock cylinder head's flow potential and would either have to go in to start porting and polishing, or install a new set of performance cylinder heads for more power.

Test 9- Speed Demon 750 carb:
Max 418 tq, 356 hp
Avg 398 tq, 294 hp
Installed Speed Demon 750 and picked up torque and horsepower all around.

Test 10-"Air gap" manifold:
Max 438 tq, 380 hp
Avg 416 tq, 315 hp
Installed Edelbrock Performer RPM "Air Gap" intake manifold, which was the best single-gain swap yet and the first test to average well over 400 lb-ft of torque.

Test 12-XE262H cam:
Max 438 tq, 386 hp
Avg 416 tq, 316 hp
Swapped in larger COMP Cams XE262H cam (262/270 adv duration, 218/224 duration @ .050, .462/.469 valve lift, 110 lobe separation) straight up and low-end power began to fall.

THE GENERAL'S PARTS
Dm needed some new heads and for our next set, we went to GM Performance Parts (GMPP) and got a set of iron Vortec castings. When compared to the stock "Camel hump" heads, the Vortec's actually dropped DM's compression by about ?-point to 9.25:1, but that didn't stop them from making 23 more horsepower. After that, we swapped also on our first set of 1.6:1 ratio rockers and were again rewarded with more power

Test 14-GMPP Vortec heads:
Max 435 tq, 409 hp
Avg 413 tq, 330 hp
Installed GMPP Vortec iron heads (Scoggin-Dickey Performance Center PN SD8060A: 64cc chambers, 170cc intake runner volume, 1.94/1.50 valves), COMP 1.5:1 Magnum roller tip rockers, and Edelbrock Performer RPM "Air Gap" manifold and made lots of extra power.

Test 15-COMP 1.6:1 rockers:
Max 440 tq, 416 hp
Avg 417 tq, 333 hp
Installed COMP 1.6:1 Magnum roller tip rockers, which further pushed the power curve up.

ROCKERS AND BIGGER CAMS
There's a lot of power to be found in rocker arms and camshafts and in that pursuit, we forged onward, testing yet another bigger cam and we swapped rocker arms until we were blue in the face.

Test 17-COMP 1.6/1.5 rockers:
Max 442 tq, 414 hp
Avg 419 tq, 335 hp
We wrestled rocker arm ratios around for quite a while and found that 1.6:1 ratio intake and 1.5:1 ratio exhaust were the best combination of all rockers tested until that point. They gave a torque improvement with no hp loss. Looking back now, Test 17 may have been the best overall combination of power and torque. Especially considering that these parts are all still low on the cost scale.

Test 18-XE268H cam:
Max 439 tq, 427 hp
Avg 418 tq, 335 hp
Next in went the next bigger COMP cam and we changed all rockers back to 1.6:1. We got the results we were expecting, more horsepower upstairs and less torque downstairs. We also tried this cam with the 1.6/1.5 rocker swap and got less power. (XE268H = 268/280 adv, 224/230 @ .050, .477/.480 lift, 110 LS)