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High Horsepower GM Crate Engine

Think of this as a Saturday Night Specail small-block with the amp turned up to 11.

By , Photography by

On our first pull, the 150hp tune netted exactly that with a 482hp peak. This left us only 18 shy of our 500hp goal, and after a discussion with Westech's Steve BrulÚ we felt brave enough to hit it with a full 200 shot. This required a simple swap to 0.082 fuel and nitrous jets with the timing yanked back to 24 degrees. All that paid off with a very successful 520hp number. You'll note that we didn't hit the nitrous until over 5,000 rpm, as we were only interested in a peak horsepower number. The advantage with nitrous flowing through a fixed orifice is that the same amount of nitrous at a lower rpm generates a tremendous increase in torque. That doesn't show up in this test, but if you look at the torque increase at 5,200 rpm, you'll see there's an additional 200 lb-ft that generate the additional horsepower. That same torque gain at 3,500 rpm would kick it up to almost 550 lb-ft. We felt those cast ring lands might fail with this much torque at a lower engine speed, so we elected to delay the nitrous until 5,000 rpm. Pulsed controllers or staged nitrous systems offer the same kind of protection.

Brule also noted how badly the engine fell off after peak horsepower with the 200 shot. This indicates the engine is maxed out in terms of what we could expect if we tried to feed this engine even more nitrous. Effectively, we have arrived at the point at which the stock exhaust ports are not capable of pushing more spent gas out, especially at high engine speed when there is less time for that to occur. This leaves a greater percentage of the exhaust gas in the chamber during the intake session, thereby reducing power. Effectively, the nitrous horsepower limit for most street engines is roughly 75 to 100 percent of normally aspirated horsepower.

We've got some further plans for our Saturday Night Slayer, including a set of forged pistons to give us some detonation durability and a better set of iron Vortec heads. This engine has far more potential with a set of better heads and the iron GM Vortec heads are both affordable and offer dramatically better flow potential. The smaller 64cc chamber will also jack the compression a little and with a good dual plane, we could be very close to 400 hp normally aspirated.

By The Numbers

Test 1:

This is the Goodwrench engine baseline using a factory Q-jet manifold and Q-jet 750-cfm carburetor with 1-5/8-inch Hedman headers and a pair of 2-1/2-inch Flowmaster mufflers.

Test 2:

The change for this test was the Summit camshaft, a new Weiand single-plane intake, and a previously owned 750-cfm Holley mechanical-secondary carburetor. Total timing was 37 degrees with 72 primary and 76 secondary jetting in the carburetor.

Test 3:

Now we get serious, bolting on the NOS Cheater system with 200hp jetting and 24 degrees of total ignition timing. The retarded timing explains why the power is down below 5,100 rpm where the nitrous was introduced.
RPM Test 1 Test 2 Test 3
TQ HP TQ HP TQ HP
2,500 265 126 318 151 310 147
2,700 269 138 317 163 311 160
2,900 310 171 317 175 313 173
3,100 299 176 330 195 316 186
3,300 294 185 334 210 320 201
3,500 307 204 341 227 324 216
3,700 348 245 348 245 331 233
3,900 336 249 353 262 333 248
4,100 325 254 355 277 334 261
4,300 310 254 354 290 335 274
4,500 296 253 350 300 332 285
4,700 276 247 345 309 330 296
4,900 259 241 341 318 338 315
5,100 239 232 335 325 379 368
5,300 218 221 326 329 520 525
5,500 -- -- 317 332 482 505
5,700 -- -- 305 331 450 488
5,900 -- -- -- -- 420 472
Peak 348 254 355 332 520 525
Avg. 290 213.1 337.6 281.5 N/A N/A

Parts list

Description PN Source Price
Goodwrench long-block, pre-'86 10067353 Scoggin-Dickey $1,499.99
NOS Cheater nitrous system 02001NOS Summit Racing 539.95
10-pound bottle fill N/A Orme Brothers 50.00
Summit budget cam SUM-1105 Summit Racing 54.95
Weiand X-celerator manifold 7547 Summit Racing 159.95
Holley 750 mech. sec. carburetor 0-4779 Swap Meet 150.00
Hedman 1-5/8-inch header, painted 68299 Summit Racing 169.95
Summit header gasket, copper 111406 Summit Racing 22.95
Summit intake gasket G2410 Summit Racing 12.95
Summit carb gasket G1418 Summit Racing 1.95
Fel-Pro head gasket 1094 Summit Racing 34.99
GMPP water neck 10108470 Summit Racing 6.95
Mr. Gasket thermostat, 180 4364 Summit Racing 13.95
HEI distributor used Boneyard 15.00
MSD HEI cap, rotor 8416 Summit Racing 26.95
Summit spark plug wire set 868836 Summit Racing 29.95
Autolite spark plugs AR132 Summit Racing 28.00
Wix oil filter 495-51060 Summit Racing 4.95
Comp Break-In oil, 10W-30, 5 qts 1590 Summit Racing 29.75
Harmonic balancer 594-012 Summit Racing 31.95
Summit balancer bolt G1677 Summit Racing 5.95
Gates water pump 43101 Boneyard 24.79
Total Rock Auto $2,915.82

SOURCES
Hedman Hedders
12438 Putnam Street
Whittier
CA  90602
562-921-0404
http://www.hedman.com
Orme Brothers Inc.
18453 Parthenia Place
Northridge
CA
818-885-1414
OrmeBrothers.com
Summit Racing
Akron
OH
800-230-3030
330-630-0240
http://www.summitracing.com/
Comp Cams
3406 Democrat Road
Memphis
TN  38118
800-999-0853
http://www.compcams.com
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2 comments
otis-larry
otis-larry

I have the same engine that was used  for the Saturday night slayer , I got it from jeggs has about 10000 mile on it. what cam and heads should I use for more hp.  no nos.

mrduck05
mrduck05

Very informative but I do have one bit of criticism. Whenever you guys build an engine with stock heads you never list the casting numbers. That info would help alot.

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