The Mouse has hatched! Our budget-conscious 383 is ready for its in-car test. In Part Four of this five-part series on building your first engine (Dec. '07), we lashed the 383 to the dyno at JMS Racing Engines and registered a peak output of 442 hp at 5,800 rpm and 436 lb-ft at 4,900. That's with a set of Patriot Super Street 215 heads, a solid flat-tappet Isky cam with 0.544/0.547 lift and 284/294 advertised duration, an Edelbrock Victor Jr. single-plane intake, and a 750-cfm Edelbrock Performer 1407 carb. For a wallet-friendly investment of just over $4,200, we got an aluminum-head, 9.8:1, billet rod-equipped Mouse that runs great on 91-octane and should continue to do so for a long, long time, thanks to its modest 6,500-rpm rev ceiling.
But as they say, you don't race dynos. What's this thing do when we stick it in a car? To find out, we grabbed Mike Morgan's 3,200-pound '69 Nova and started spinning wrenches. You might remember our original intention, to test this mill in a '66 Chevy II, but those plans fell through at the last minute. All the same, the cars are similar test beds (frontal area, curb weight), so the impact on the results is negligible, though we did make an interesting oil pan discovery. (More on that in a minute.)
Here's the punch line: On the Superior Automotive Dynojet chassis dyno, the 383 delivered 353 hp at 6,100 rpm and 331 lb-ft at 5,250 to the tires. Newbies might wonder where all the power went. After all, a drop of 89 hp and 104 lb-ft doesn't go unnoticed. But you must remember that it requires horsepower to turn the transmission, spin the driveshaft, twist the ring gear, and rotate the tires. Parasitic losses build up quickly; by most accounts, you can expect a 20-25 percent drop in measured output at the rear tire versus the crankshaft. And there's also the question of mufflers. Sure, Morgan's Nova runs a pair of massive 3.5-inch Borlas and a Dr. Gas X-pipe, but there's still a bit of backpressure entering the picture compared to the straight-out header exits used on the engine dyno.
Quick Notes
THE TEST
In-car performance on the chassis dyno and at the dragstrip
BOTTOM LINE
It's all in the combination.
Engine installation is easiest...
Engine installation is easiest if the transmission is already in place under the car. Never use the torque converter to support the transmission, as pump bushing damage can result. Instead, support the case at the leading edge of the transmission pan. Naturally, take care not to smack the distributor into the firewall.
The guys at JMS turned us...
The guys at JMS turned us on to some new exhaust header gaskets from Percy's. We installed a Seal-4-Good aluminum gasket on the driver side. Made of soft aluminum, these gaskets conform to the cylinder head and header flange when compressed and require no sealant. Sold as PN 66012, these reusable gaskets are ideal for situations in which the headers will be removed repeatedly. They can even be port matched. We followed the directions and retorqued the header bolts several times after warm-up.
For comparison, we installed...
For comparison, we installed a Percy's XX carbon gasket (PN 68012) on the passenger side, and it also provided a completely leak-free seal. Made of woven carbon-fiber cloth, these things feel like thick velvet but resist burning at even 2,000 degrees F. Percy's claims an "ultimate seal on even the worst surfaces." While our Patriot heads are finely machined all over, these XX carbon gaskets would have been cheap insurance on the lumpy factory iron head castings we showed you in Part Two (Oct. '07).