Engines are not that much different than people in that both can only be pushed so far before they break. Luckily for us, our favorite engine shares a lot in common with our favorite people, especially the part about letting us push it past its limits. Danger Mouse (DM) has become so well known around these halls that it's practically thought of as one of the family now. And lately, we've been pushing it extra hard in search of extra power. Thankfully, it didn't break, but it began to fall down.
Even though DM can't talk, after the last dyno test at Vrbancic Brothers Racing it was obvious that the 1,000-plus dyno pulls DM has logged in its career were taking their toll. A decision had to be made and it had to be made fast. Would we continue testing until DM croaked? Or would we put him out to pasture like so many other magazine engines before? Or should we rebuild him fresh and make a new start on another year? The answer was pretty simple. We're hard-core for power and there's no way we were going to let DM turn old and gray gracefully. Nope, we intended to bend him and try to break him again this year and the only way to do that would be by rebuilding him first.
Right away we contracted with a very well known and respected engine shop in our neck of the woods to see if they could rebuild DM in time to keep us on schedule. The crew at Speed-O-Motive stepped up to the challenge and even signed on for the duration of this year's event. Meaning that they'll do the all wrenching and they'll also be doing most of the testing on their new DTS engine dyno. It was about time we handed over the multitude of chores involved with building and maintaining a monthly dyno mule and Speed-O-Motive was eager to tackle the task.
Rebuilder's Log, Date:January 2004After we dropped DM off at Speed-O's new West Covina, California, facility, owner George Ullrich took one of his best guys, Mitch Jackson, off of full-time engine-building duty to supervise as DM's Number One tech. From here on out, Mitch would also be getting help from our own Seth Millhollin, who puts in some part time work around the shop, (you're foolin' if you think these magazine gigs can pay all the bills) and the rest of the Speed-O crew.
Mitch tore DM down to find a few mangled bearings and some bits of broken distributor gear teeth in the bottom of the oil pan. The teeth came from a gear that sheared its teeth off one day on Westech's dyno. We yanked the distributor and replaced the gear and were up and running again in about 20 minutes. It was all over so fast that we forgot about where the broken parts end up and never pulled the pan to remove them. Yep, we were a bit lazy and there's really no way we'd ever condone running and engine after something like has happened. But, hey, that's why this is a test mule.
Mitch thinks that a few tiny, ground up pieces of distributor gear might have gotten past the oil filter and into the bearings, causing some wear and tear. Luckily, the crank and rods were fine and all DM needed, besides a new set of Speed-Pro bearings, was a quick pass with the block hone to scuff up the cylinder bores for a new set of Speed-Pro moly rings.
While the engine was apart, we also decided to exchange the pistons with a new set that Lunati made for us immediately after we'd put DM together the first time. The new pistons have a taller compression height (1.595 versus the old 1.555), meaning they sit higher in the bores, to correct the very low, -0.040 deck clearance the first set of pistons made.
That's because those pistons were stock-replacement slugs designed to be used in older blocks that had already been decked. But DM's brand new Mowtown block came delivered with a true 9.035-inch deck height and made that set of pistons sit too far down the bores. At the time, we left it alone because it more closely approximated what might be on the street today. Given that many engines have never been rebuilt for performance and might still have the low deck height that GM installed.
The new, taller slugs put DM's pistons right at "zero" deck, which is what we like to see for the best possible power. In addition, they also raised DM's compression by a little more than a half point. Other than the new slugs, DM was put back together just like it was the first time. The file-fit Speed-Pro rings were gapped a little wider than standard to accept some extra abuse and a pair of steel O-ring Fel-Pro heads gaskets (PN 1003) were clamped on top.
For its next bash on the dyno, we will retest the Holley Street Avenger TBI fuel injection system that we had tried before. To make DM more TBI friendly, Speed-O installed a smaller Lunati hydraulic cam and some World Products Sportsman II iron heads. Then they topped it off with a Holley Street Avenger dual plane intake manifold to give the TBI the strongest signal possible. We asked Speed-O to reuse the COMP Cams 1.5:1 magnum roller rockers button up the ignition with a new computer-controlled electronic distributor from Holley.
We figured even though this equipment might not break any records in the horsepower deparment, it would definitely complement the low-speed torque characteristics of the street-worthy TBI. Who knows, we might break a new low-end torque record with this set up. You'll just have to wait until next month to find out. Because that's when we'll head back to Vrbancic's dyno once again to see if we can make the TBI fly.
Danger Mouse Rebuild Specifics For Part 16Compression: 9.1:1World Products: Motown block 4.030 boreWorld Products: Sportsman II iron heads 64ccLunati: hydraulic flat-tappet cam PN50179LUN (268-279 degrees advertised duration, 215-224 degrees duration at .050, .489/.489 lift, 112-degree lobe separation, 108-degree intake centerline)Lunati: crank, rods, and flattop pistonsHolley: dual-plane manifold PN300-36 Speed-Pro: rings and bearingsFel-Pro: gasketsMilodon: oil system and fastenersSpeed-O-Motive: assembly