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Chevy 396 Big Block Engine Buildup - The Big EasyGiving Our Old 396 New Life... Again! From the February, 2007 issue of Classic Trucks By Rob Fortier
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Most of you may recall the Chevy big-block buildup we did last year with a mid-'60s 396 at Speed-O-Motive (May '06). Well, while 385hp may be sufficient for some, this Rat wasn't satisfied with Mouse numbers. As mentioned in the story, the valvetrain would eventually be addressed, swapping out the mild cam and springs to give the now 440-cubic-inch engine more elbowroom. Well, eventually is now the present, and we're about to see what this workhorse really has in her. We didn't want to overstay our welcome, so we decided to take the 440 out to Steve Brule at Westech in Mira Loma, California, for round two with the big-block. After seeing the numbers the engine produced, he was sure he could easily get an additional 75hp, if not more, with a relatively simple cam, valvespring, intake manifold, and carburetor swap. As a matter of fact, he was more determined than ever since he suspected something might be going on internally, something that limited peak horsepower the first go-around. Sometimes, more is good-at... Sometimes, more is good-at least in this case. Had we not wanted to squeeze more horsepower from our old 396, we would have learned the hard way that the undersized rings weren't clenching the cylinder walls with enough tension, thus allowing substantial leakby (20 percent on all eight). Once we dropped the engine off, Steve first performed a leak-down just to see if there was any truth to his suspicions. Later that day, we got a call from him with the news, "20 percent on all eight cylinders." Being relatively high, but not totally extreme, the rings weren't biting on the cylinder walls like they should, thus allowing compression and oil to leak by. Obviously, the heads needed to be pulled to further probe the situation-and once they were, Steve's intuition was dead on, as each piston was evenly coated with oil. There was no turning back from here...at least not if we wanted to move forward with the initial game plan. After Steve pulled the first piston out, what had been holding the engine back was finally revealed. Without getting into too much detail, it turned out the individual who initially started the project had ordered, and subsequently installed, the wrong size rings (undersized, with a 0.120 end gap) before having Speed-O-Motive finish up the long-block. Had we run the engine on their dyno a few more times, we would have seen the peak horsepower numbers decrease each run, which would have tipped us on to any potential problems. However, we didn't want to bog down their dyno for too long, so we were content with the initial runs, paid our bill, and went on our merry way. (It should be noted that Speed-O-Motive offered to fix the problem when they learned of it, even though it was not their fault.) OK, so the problem was isolated and, fortunately, the fix was simple-install new rings and move on. The problem was caused by... The problem was caused by a .120 ring end gap, which was due to an error in the early stages of the project that no one knew about...until now. No harm, no foul. And that's what Steve did-he ordered the correct rings, installed them, and buttoned the lower block back up. Now we could finally get to getting...more horsepower, that is. And that all started with the installation of the COMP Cams hydraulic roller camshaft. And being that the engine was a little light on the spring side, he strongly suggested COMP's Beehive valve- springs. The valvetrain upgrade also included new lifters, pushrods, and roller rockers, and while he was at it, he swapped the gear drive for one of COMP's double-roller timing chains. The 440 was previously equipped with a complete Edelbrock Performer package that was absolutely perfect for a daily driver, but this engine isn't going to end up in anything like that. Instead, the Performer intake was traded out for an RPM Air-Gap, and the 750-cfm carb was swapped for a Mighty Demon 750. Other than that, the rest of the components remained the same from the first buildup. With everything back together, the revived Rat was bolted up to Westech's SuperFlow dyno to see if Steve's horsepower increase predictions were even in the ballpark. Well, as it turned out, he was a little off-by at least 50hp. Much to everyone's surprise, the 440 produced an admirable peak 515hp @ 5,700 rpm and 542 lb-ft @ 4,300. Now that's what we were looking for. We managed to build a driver-friendly version that even the most throttle-friendly could enjoy-and now we've turned it into a powerhouse the average lead foot would kill to have under their hood.  The old valvetrain wasn't...  The old valvetrain wasn't sub par by any means, but it did have its limitations power-wise. The conventional COMP Cams springs will be replaced with more efficient Beehives, while the Magnum roller rockers will give way to beefier Pro Magnums.  Westech's Steve Brule calculated...  Westech's Steve Brule calculated our engine specs to the T before ordering/installing new Sealed Power rings on our 9.5:1 Keith Black pistons. While the engine was touted as a 434 in the first installment, Steve's math revealed its true 440-cubic-inch displacement, and we weren't about to argue with that.  Fortunately, since the engine...  Fortunately, since the engine was only dyno-run a few times prior, the cylinders did not require re-honing.  With the exception of a one-piece...  With the exception of a one-piece oil pan gasket and replacing the gear drive with a COMP double-roller timing chain, the short-block went back together just as it was before.  COMP's Beehive valvespring...  COMP's Beehive valvespring might not appear as strong as its conventional type, but don't let looks deceive. The reduced spring mass and Super-Clean ovate wire give the springs more valve control with minimal pressure. What that means for the big-block is a greatly increased rpm band and more horsepower.  Since we were sticking with...  Since we were sticking with COMP components, the studs and guide plates remained in service, ready to take on the Pro Magnum rockers.  With the right stall converter,...  With the right stall converter, Edelbrock 110cc oval ports will survive on the streets just fine with pump gas. But with the new COMP valvetrain, they'll be passing that gas like never before.  Unless you have an early 396...  Unless you have an early 396 block like ours, you won't need to worry about the rear oiling groove. If you do, though, COMP can provide the appropriate cam. Steve chose COMP's Xtreme Energy XR282HR cam for our engine, a hydraulic roller with a 230/236 duration and a 2,200-5,600-rpm operating range.  Steve brought the No. 1 cylinder...  Steve brought the No. 1 cylinder to TDC in preparation for degreeing the cam once it was installed, as well as to verify that the pistons would not enter too far into the cylinder quench area.  COMP's upgrade package also...  COMP's upgrade package also included the Pro Magnum hydraulic roller lifters designed to hold position at high engine speeds, thus preventing the valves from opening when they're not supposed to be.  The 8650 chromoly Pro Magnum...  The 8650 chromoly Pro Magnum roller rocker arms are unbeatable when it comes to durability in high-revving engines.  The rebuildable rockers' bodies...  The rebuildable rockers' bodies carry a lifetime warranty from COMP Cams, too.  Though our old Performer intake...  Though our old Performer intake looked great in its EnduraShine coating, we had to shelve that in favor of an Edelbrock RPM Air-Gap intake if we were going to achieve the performance results we were after.  For the person who likes to...  For the person who likes to bolt on and go, there's no beating an Edelbrock carburetor, period. But if you're more prone to tuning, there are other options. Obviously, tuning is what Westech does, and for this application they wanted to try out Barry Grant's Mighty Demon 750.  With the internals out of...  With the internals out of the way, Steve bolted up the remainder of the externals, including the PerTronix points-style electronic distributor, Mooneyes valve covers, and Performance Products harmonic damper (the electric water pump is for dyno purposes only). Now it was time to see what the 440 could really do.  Strapped to Westech's SuperFlow...  Strapped to Westech's SuperFlow dyno, our big-block passed the tests with flying colors: a peak 515hp @ 5,700 rpm and 542 lb-ft @ 4,300! That's quite a bit more improvement than the initial 75hp gain Steve anticipated, and we're a bit more than pleased with that...for now!
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