The low peak-rpm numbers are also indicative of the low static compression. The deck height's being more normal would have created roughly 9.5:1 compression, which would have kicked the power curve up in the rpm range, and all the power numbers (both torque and horsepower) would have been drastically greater. Because the pistons were sunk so far down in the hole, there was no way to machine the block to repair that problem. The correct way would be to add a 5.7-inch stroker rod and custom piston with a D-shaped reverse-deflector-style dish that would create somewhere around a 10.0 to 10.5:1 static compression ratio with a tight quench to the head using the zero deck approach. That would drastically improve the compression, the quench, and the power. THUMPR CAM SPECS CAMSHAFT DURATION AT 0.050 LIFT LOBE SEPARATION Comp Thumpr hyd., intake 235 0.490 107 Exhaust 249 0.475 POWER CURVES TEST 1 TEST 2 CHANGE RPM TQ1 HP1 TQ2 HP2 TQ HP 2,600 401 198 402 199 - 1 - 1 2,800 395 210 392 209 - 3 - 1 3,000 391 224 389 222 - 2 - 2 3,200 407 248 410 249 - 3 - 1 3,400 428 277 433 280 - 5 - 3 3,600 441 303 447 307 + 6 + 4 3,800 448 324 457 331 + 9 + 7 4,000 447 341 458 349 +11 + 8 4,200 443 354 452 361 + 9 + 7 4,400 434 363 444 372 +10 + 9 4,600 423 370 438 383 +15 +13 4,800 410 375 430 393 +20 +18 5,000 394 376 418 398 +24 +22 5,200 375 372 404 400 +29 +28 5,400 356 367 390 401 +34 +33 5,600 375 399 5,800 355 393 6,000 333 380 Peak 448 376 458 401 Avg. 412.6 320.4 414.0 336.3 Column averages used the entire curve with data every 100 rpm, which does not appear on this chart. Here's the 400 with the stock Vortec heads on the dyno at Westech. We retained the stock Vortec springs to break in the cam. With the stock Vortec heads, the low-compression 400 managed to make 376 hp and almost 450 lb-ft of torque.Here's the 400 with the stock Vortec heads on the dyno at Westech. We retained the stock V Swapping on the Vortec Bow Tie heads was a relatively simple process. We also added a Weiand Speed Warrior dual-plane along with different valve covers to give the big heads a different look. The bigger heads pushed the power up over 450 lb-ft of torque and 400 hp.Swapping on the Vortec Bow Tie heads was a relatively simple process. We also added a Weia « | 1 | 2 | 3 | 4 | 5 | » | View Full Article By Jeff Smith Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
68post 12/28/2012 at 6:56 AM I agree with phill30. How about flattops for compression and E85, exhaust porting and a small single pattern cam ? After proper machine work.500 ft lbs and 500 hp should be easy. This was an exersize in what NOT to do !
Bigugly_1. 8/24/2011 at 2:31 PM JR Motorsports has a 400 assembly like this for about the same money with a warranty!http://www.jrmotorsports.com/subCategory.cfm?subCat=803&cat=60
phill30. 7/23/2011 at 7:50 PM I really looked forward to this article but was disappionted with the results. I would like to see this project done again, but this time build the engine right without so many compromises, ie. deck height, bore wear. Then compare it to an identically equiped 383 to show everyone what they could have instead. I beleive the 400 market would heat up.
