It's been quite a long time since you've read about The Coolest Rat. More than a year, to be exact, (see: SC March 2003, pages 34-38, for Part 2), but sometimes, that's how things go in the magazine business. It's not that we didn't love building and testing this beast, to the contrary, it's been one of our finest and most successful engines ever. It's just that other things got in the way.
Suffer no longer faithful readers, because The Coolest Rat is back. If you're unfamiliar with its past, The Coolest Rat is the stroker big-block equivalent to a 383-cid small-block. That is, all it takes to build one is a .060-over 454 block and a 1/4-inch longer than stock, (4.250-stroke), crank. Throw in some new pistons hung on 1/4-inch longer rods, (6.385-inch), and you've built yourself a killer 496-cid big-block. But, to make this motor quite a bit more interesting than any ordinary stroker mill, we built it with Holley's multi-port electronic fuel injection system (MPI) and a big Lunati hydraulic roller cam for rumble.
For this much power, we knew we needed a bigger cam, too. Lunati ground this mighty-big hydraulic roller for us with 255/265 duration at .050, .629/.629-inch lift, and 114-degree lobe separation.
Since the cam was pretty big on its own, we kept rocker ratio at the stock BBC 1.7:1 with these Lunati aluminum rocke
DYNO FIGURES
We hauled the Coolest Rat back over to Vrbancic Brother's Racing to bolt it onto their DTS engine dyno for another day's flogging. Now since EFI is able to adjust its fuel delivery curve accordingly, the fuel map we'd created for the last combination was close enough to get us going. But some time spent tuning with the laptop netted us more power in the entire rpm range. The biggest improvements were in the low end. By altering the fuel and ignition maps in Holley's Commander 950 ECU, we tuned in more than 38 extra ft-lb of torque at 4,400 rpm. That's the coolest thing about EFI. Once you've got the engine running on the dyno, you never even have to leave your chair to make tuning adjustments. We spent about 3 hours tuning the motor and never once even opened the dyno cell door. While we never made it to 700 hp, 697 is close enough in anyone's book.
اخيراً الخلطه العجيبه هههه
ENGINE COMPONENTS FOR THE COOLEST RAT PT. 3
This is a list of the pertinent pieces for this Rat's buildup. While you could substitute some pieces, we wouldn't stray too far, lest you'll suffer power losses and idling woes.
Bearings: Speed-Pro
Block: GM factory 2-bolt 454
Bore/Stroke/CID: 4.310/4.250/496
Cam: Lunati HR custom 255/265 @ .050, .629"/.629", 114 LS
Chain: Lunati billet (PN 93116)
Compression: 10.4:1
Connecting Rods: Trick Flow 6.385" (PN TFS-37638500)
Crank: SCAT 4130 nitrided steel (PN 5-454-4250-6385-2)
Dampener: TCI (PN 870005, internal balance)
Distributor: Holley Annihilator (PN 890-160)
EFI: Holley Commander 950 MPI, 50 lb-hr injectors (PN 300-515)
Head Gaskets: Fel-Pro (PN 1017-2)
Heads: AFR 315CNC (114cc chambers), springs (Lunati PN 73021), Ti retainers (Lunati PN 76113)
Ignition: Holley Commander 950
ECU-controlled distributor
Intake manifold: Holley (PN 9901-202)
Lifters: Lunati HR (PN 72820)
Oil System: Moroso kit (PN 22185)
Pistons: Lunati (PN 1515U4S6)
Plug wires: Holley (PN 50-9801)
Pushrods: Crane custom 3/8" (7.780" intake, 8.760" exhaust)
Rings: Speed-Pro Moly
Rockers: Lunati 1.7:1 (PN 84174)
Spark Plugs: Autolite (PN AR3923)
Throttle body: Holley 2,000-cfm (PN 112-538)
Timing cover: COMP Cams 2-piece aluminum (PN 212)
AFR HEAD FLOW
315CNC intake port, 114cc chamber (reduced from standard 121cc), 2.25" Ferrea intake valve, 1.88" Ferrea exhaust valve, flowed with 2 1/8" exhaust tube @ 28" water depression
انتهينا ....
