The motor in the Coronet needed to be freshened up since I hadn't had it apart since 1998. So instead of just rebuilding it, I decided to go all out and build a stoker motor. Luckily, both big and small block Mopar engines have high deck heights and raised camshaft centerlines so there's plenty of room in the crankcase for stroker cranks and high strength rods. So with a 4.25 in. stoke vs. the stock 3.38 in. stoke, the displacement grows from 383 cubic inches to 496. While I was at it, I also decided to upgrade to a hydraulic roller camshaft and Stealth aluminum cylinder heads. The nice things about all of these mods is that they increase the output of the motor but don't change the outward appearance of the motor. I'd say that's having your cake and eating it too.
Pic 1: Motor coming out and ready to go to Magnum Machine in Chesapeake. Notice the load leveler which allowed the motor and transmission to come out as a unit and clear the radiator support.
Pic 2: Assembled shortblock on the engine stand. Notice the dished pistons which were necessary to keep the compression ratio at 10.5:1. Believe it or not, that ratio is fine for premium fuel and aluminum heads on a carbureted motor. Of course, you have to tailor your camshaft to that compression ratio in order to keep the cylinder pressure in a safe range.
Pic 3: Pic of a Stealth head. With minor port work (which I had done), the intake ports flow around 280 cfm @ 28 in. water. That's enough to support about 560 HP. The exhaust ports flow around 220 cfm, which is quite an improvement over the stock heads. All in all, I'd say that these heads are a good "bang for the buck", especially when you add up the cost of rebuilding and extensively porting the stock, cast iron heads. An added bonus of the Stealth heads is that they look almost exactly like the stock heads (unlike the Edelbrock Performer heads) and shave about 70 lbs. off the engine weight.
Hope the group enjoys my project.
Thanks,
Martin
UPDATED MARCH 19TH
Yesterday I had my motor on the engine dyno and I'd like to share a pic of it and the dyno results, so could you please add the pic and this description:
Who said that big block Mopars can't make any power? The engine dyno results speak for themselves. On the first pull, the motor made 509 HP and 610 lb-ft of torque. By tweaking the jetting and timing, we were able to get the power up to 521 HP and 628 lb-ft of torque. On the last pull, I tried a new Holley Ultra HP 850 cfm double pumper carb. The motor liked it and turned in the best numbers of 528 HP and 637 lb-ft of torque. Even more amazing is the torque at low rpm - it made 570 lb-ft at 2500 rpm! Can you say torque monster? Can't wait to see how it feels in the Coronet.
Pic 1: Motor coming out and ready to go to Magnum Machine in Chesapeake. Notice the load leveler which allowed the motor and transmission to come out as a unit and clear the radiator support.
Pic 2: Assembled shortblock on the engine stand. Notice the dished pistons which were necessary to keep the compression ratio at 10.5:1. Believe it or not, that ratio is fine for premium fuel and aluminum heads on a carbureted motor. Of course, you have to tailor your camshaft to that compression ratio in order to keep the cylinder pressure in a safe range.
Pic 3: Pic of a Stealth head. With minor port work (which I had done), the intake ports flow around 280 cfm @ 28 in. water. That's enough to support about 560 HP. The exhaust ports flow around 220 cfm, which is quite an improvement over the stock heads. All in all, I'd say that these heads are a good "bang for the buck", especially when you add up the cost of rebuilding and extensively porting the stock, cast iron heads. An added bonus of the Stealth heads is that they look almost exactly like the stock heads (unlike the Edelbrock Performer heads) and shave about 70 lbs. off the engine weight.
Hope the group enjoys my project.
Thanks,
Martin
UPDATED MARCH 19TH
Yesterday I had my motor on the engine dyno and I'd like to share a pic of it and the dyno results, so could you please add the pic and this description:
Who said that big block Mopars can't make any power? The engine dyno results speak for themselves. On the first pull, the motor made 509 HP and 610 lb-ft of torque. By tweaking the jetting and timing, we were able to get the power up to 521 HP and 628 lb-ft of torque. On the last pull, I tried a new Holley Ultra HP 850 cfm double pumper carb. The motor liked it and turned in the best numbers of 528 HP and 637 lb-ft of torque. Even more amazing is the torque at low rpm - it made 570 lb-ft at 2500 rpm! Can you say torque monster? Can't wait to see how it feels in the Coronet.
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