super stock
Joined: Jan 2003
Posts: 931
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[quote} But Mike , there is a mopar muscle article from back in the early part of the last decade that made it look easy as pie ....  ... I know it is not an easy feat , though many think it is .
Well, John, I guess if you are referring to this story your memory might be failing you. I don't see 425 hp with stock exhaust manifolds and intake manifold.
383; RESTO TO RAD
Building Mopar’s Underrated Big Block
Text and Photography by Steve Dulcich
What’s not to like about the 383? It seems that these engines have fallen somewhat out of favor in recent years as attention has turned to big blocks of ever increasing cubic inches. For a moderate investment, a 383 can be built into a sweet high-revving powerhouse. Study the 383’s numbers compared to the popular engines of the competition. The 383 carries a bore and stroke of 4.25”x3.375”, while the 396 Rat had a embarrassingly undersized bore of 4.094”, and a 3.766” stroke - as long of an arm as a 440. At the Ford camp, the 390 was even worse, with a bore only slightly bigger than a 340 at 4.050”, and again a 440ish stroke length of 3.780”. The 383 was a thoroughbred by comparison to the competition’s similarly-sized big blocks. In fact, the FE Ford fan’s coveted 427 block had less bore diameter than the dirt-common Mopar 383. Even the Chevy guys’ big guns, the 427 rat and the 454 had bores no bigger than Chrysler’s 383. You won’t see Ford or Chevy fans passing up 427 FE's or 427 and 454 Rats, but we tend to walk by those 383s with nary a second look. Why?
We decided to explore the 383’s hidden potential. Anyone who remembers the 383 equipped musclecars knows that these engines can run. Garden variety 383 RoadRunners, Superbees, Challengers, ‘Cudas and A-bodies vastly outnumbered the more exotic Hemi and Sixpack cars back in the day, and these 383 cars contributed far more to the musclecar mystique and legend than they are given credit for today. We decided to put a 383 together to blueprint-stock specs, and see just how much power a stock 383 put out. We also know that the 383 was one of the most modified engine ever installed in performance cars, responding eagerly to basic bolt-on speed equipment. To tap into that potential, we’ll baseline the stock engine on the dyno, and then use some of today’s best performance hardware, taking our 383 from resto-stock to racy-rad.
THE BUILD
Our goal was to start with a stock-spec 383, built to match the 383 Magnum engines of yesterday. As we started with a well-worn core, the crank was already ground down to the minimum, and the block was already bored .030”. Taking the block out to .060”-over didn’t have us worried, but we were still left with finding a crank. We tapped into PAW’s extensive catalogue for their SuperStock master kit, which includes a crankshaft, rods, pistons, rings, bearings, gasket, oil pump, timing set, cam, and lifters – basically everything we would need to make our 383 as good as new. A few upgrades we made to the base kit, including custom balancing, moly rings, chrome moly rod bolts, and a high volume oil pump. These low-cost options on the PAW kit were well worth the price for the sake of performance and reliability.
Also on our list of upgrades was a set of KB-162 Hypereutectic pistons. These pistons are designed to give approximately the stock compression ratio, but have generous valve notches allowing us to move to a fairly aggressive camshaft later on. For the baseline, a Resto-spec Mopar Performance “RoadRunner” cam and lifter package were specified as an extra cost option, since we were looking to duplicate a factory 383 Magnum for our initial configuration. We were also short an oil pan, so a PAW unpainted steel replacement sump was ordered, along with a dipstick and tube kit. Even though we were starting with little more than the original block, the PAW kit made building a balanced and blueprinted 383 bottom-end surprisingly affordable, and very easy.
With the required parts in hand, all we had to contend with was the block machining. The block was handed off to Jim Grubbs Motorsports, in Valencia, CA. Jim’s crew cleaned our 383 block, bored the block, and honed it with torque plates to fanatical precision. The block was decked squared to the crank centerline using a BHJ indexing fixture on Grubbs’ Rottler mill. A cut of .010” on our previously machine block gave us a zero deck height with our KB Hypereutectic pistons. That’s all the machining we needed for this project. We already had a set of fresh #906 cylinder heads, rebuilt to stock specs with the original 2.08/1.74” valves, which we had previously rebuilt ourselves with new guides and a Serdi valvejob.
Using the PAW kit and Grubbs-machined block we had all the components ready to put together our 383 in a remarkably short time. Since this was to be a basic stock rebuild, the actual assembly was very quick, simple and trouble-free. The stock #906 heads were milled .020” to compensate for the thicker replacement head gasket, reducing the chamber volume from the stock 87 to 83cc. The deep valve notches in the KB pistons (6cc) coupled with the 84cc open chamber heads gave us a compression ratio of 9.2:1. Overall it was a 383 just like Chrysler used to build. We gathered up an original 383 Magnum AVS carb, the correct #666 iron intake manifold, a real set of factory high performance exhaust manifolds. Overlooking the Mopar electronic ignition distributor, installed more for reliability than performance, our 383 on the engine stand was like artifact from the past. We had only one question … How much power would it make?
TRUTH OR LIES
Much has been said of the horsepower numbers game in the musclecar era. Sometimes the claim is made that the gross ratings were wildly optimistic. In some cases, the assertion is that certain engines were “Seriously under-rated”. We’ve been here before, and generally found that Chrysler was fairly accurate in its ratings compared to dyno numbers we’ve seen on stock engines. We dutifully loaded our 383 onto the SuperFlow dyno at Westech to see how many of the factory-rated 335 horses were real or imagined. The 383 sparked instantly to life, and we were struck by how mellow it sounded through the factory manifolds. After the customary break-in cycle, we let the 383 fly. The readout at the end of the pull showed 335.2 HP @ 5000 RPM, and 392 Ft lbs @ 3600. 335 HP indeed. We adjusted the timing from 35 degrees total to 38, and ran a couple of back-up pulls. The 383 responded with 338 HP @ 5000, and 394.6 ft lbs @ 3600 RPM. No, Ma Mopar wasn’t lying when she hung the numbers on the high performance 383.
POWER MODS
While 338 HP for any stock engine is very respectable, we really wanted to explore the power producing potential of the 383. This time around, we would keep the basic 383 long-block package stock, but shake out some of the power hidden within with basic bolt-ons. Our first target was the same chosen by countless thousands of 383 owners over the years, adding a set of tube headers. We pulled down the magnum manifolds and replaced them with a set of Hooker #5101-1 headers. Was much to be gained over the sleek high performance manifolds? The headers added a solid 15-25 ft lbs of torque across the full range of our test RPMs. That’s added power you’d definitely feel.
Next, we set our sights on the original AVS carb. We went straight to kill here with an 850 Demon carb. The 850 may be considered too much at this mild state of tune, but with our subsequent modification plan, it would be just enough. The added airflow was a definite improvement, with the 383 now edging up to 367.2 @ 5100 RPM, and 434 ft-lbs @ 3600. Contrary to conventional wisdom, we found the big carb actually added substantially to torque in the lower to midrange, up as much as 25 ft lbs. The top-end numbers were also up, the gains weren’t as dramatic. We knew exactly what was holding the 383 back at higher Rpm’s, that big heavy chunk of cast iron sitting under the carb.
To unlock the 383s breathing efficiency, our next mod was to swap the stock iron intake for Mopar Performance M-1 single plane manifold. With the intake change, the visual character of our 383 was transformed. It was finally looking like a performance mill. Our next pull showed that looks were more than skin deep, with the dyno numbers now catapulting to 406 HP @ 5400 RPM, and 433 ft-lbs @ 4000. True to form, we lost a handful of ft-lbs down low in going from a dual plane to a single plane, but we gained huge up top. Yes, 383s can make power, and make it cheap. We had a rebuilt stock engine, with headers, a carb, and intake, and were churning better than 400 HP. We were impressed.
Our final mod, not surprisingly, was a good old-fashioned cam swap. There was, however, nothing old-fashioned about the grind. Competition Cams has recently introduced a line of Mopar specific high-lift camshafts. We were eager to try one of the new Comp bumpsticks, and ordered up an XE285HL-10. This is a fairly serious hydraulic profile, rated at 285/297 degrees gross duration, and specing out at 241/247 degrees duration @ .050”, with .545”/.545” lift, on a 110 degree lobe separation. The cam was degreed-in at four degrees advance, and topped with a set of matching Comp lifters. We upped the valvesprings at the same time to Comp’s # 924 dual-spring assemblies, since the high-lift cam requires much more spring than the stock 383 cam. We were still budget-conscious with this engine, and elected to retain the stock 383’s valvetrain.
Back up and running with the big stick, the 383 had a much weightier thump. With the stock heads the cam would likely not realize its full potential with our present combo, but we still expected a gain, and expected to pull higher RPMs. With that in mind, the dyno controls were reset to 6200 RPM, and we opened the 383 up once again. It pulled cleanly through the revs, and we now had a 455 HP 383. Peak power was actually 454.9HP @ 6000 RPM, and 456.6 ft lbs @ 4800. With the big cam we lost 5-10 HP at the bottom of our test range, but from the midrange up the Comp stick just pulled away like a freight train, posting a gain of nearly 50 HP. The useable RPM range of the engine was extended by better than 500 RPM in the bargain. We have to say we were impressed with the 383. Stock other than headers, cam, intake, and carb, we were solidly over 450 HP. That’s dollar value per horsepower.
DYNO RESULTS
HORSEPOWER
SUPERFLOW 901 DYNO
TESTED AT WESTECH PERFORMANCE GROUP
TORQUE
RPM STK HDRS CARB INTKE CAM
3000 382.7 406.3 427.1 405.5 394.2
3200 388.1 406.6 422.6 410.9 400.0
3400 388.3 412.6 431.9 421.2 414.7
3600 394.6 411.2 433.7 426.1 431.5
3800 392.4 408.3 430.8 430.0 435.5
4000 387.2 401.3 424.6 433.0 446.5
4200 377.8 396.2 416.4 430.1 451.5
4400 371.4 390.2 409.7 430.1 451.8
4600 367.8 384.6 402.0 427.8 454.2
4800 361.6 379.5 398.5 424.3 456.6
5000 355.1 373.4 385.6 421.3 450.3
5200 337.2 357.8 368.1 407.7 449.1
5400 322.8 348.5 351.4 395.1 435.8
5600 xxxxx xxxxx xxxxx xxxxx 417.0
5800 xxxxx xxxxx xxxxx xxxxx 407.6
6000 xxxxx xxxxx xxxxx xxxxx 398.2
HORSEPOWER
RPM STK HDRS CARB INTKE CAM
3000 218.6 232.1 244.0 231.6 225.2
3200 236.5 247.7 257.5 250.3 243.7
3400 251.4 267.1 279.6 272.7 268.5
3600 270.5 281.9 297.3 292.1 295.8
3800 283.9 295.4 311.7 311.1 315.1
4000 294.9 305.6 323.4 329.8 340.0
4200 302.1 316.8 333.0 343.9 361.1
4400 311.1 326.9 343.2 360.4 378.5
4600 322.2 336.8 352.1 374.7 397.8
4800 330.5 346.8 364.2 387.8 417.3
5000 338.0 355.5 367.1 401.1 428.7
5200 333.9 354.2 364.5 403.7 444.6
5400 331.9 358.3 361.3 406.3 448.1
5600 xxxxx xxxxx xxxxx xxxxx 444.6
5800 xxxxx xxxxx xxxxx xxxxx 450.1
6000 xxxxx xxxxx xxxxx xxxxx 454.9
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