Don Terrill’s Speed-Talk

grandsport51 wrote: ↑Sun Oct 15, 2017 9:17 pm [/list][/list]Year: 1969
Ford Boss 302 Vs. Chevy DZ 302
The history of the Trans-Am series is well documented. Unfortunately, the actual performance, or at least the real power output, of Chevy’s and Ford’s sub-5.0L street motors is somewhat less so. It seems that every article ever written about either the Boss 302 or the DZ 302 always mentions the same thing: Though originally rated at 290 hp, these 302s made as much as 400 hp. Checking out the spec box, we see that the DZ 302 was essentially a 302ci version of the 365hp 327, sharing the 11.0:1 compression, Fuelie heads, and even the Duntov 30-30 cam. Also present were the aluminum high-rise intake and Holley 780-cfm carb. As impressive as the specs were on the Chevy 302, Ford’s Boss 302 stepped up things with a pair of production four-barrel Cleveland cylinder heads that flowed as well as a fully ported set of Chevy race heads of the period. Compared with the Chevy, the Boss 302 was down slightly in compression (10.5:1 versus 11.0:1) and down in cam duration at 0.050 (228 degrees versus 254 degrees) but up in valve lift (0.514 versus 0.485). Both shared impressive induction systems, but the Boss 302 heads allowed it to not only overcome the deficit in compression and cam timing but also actually outperform the Chevy 302.

Our pair of 302ci small-blocks was run at Westech on the Superflow 902 in the same configuration, meaning no accessories, an electric water pump, and 1 3/4-inch, long-tube headers. Both motors were run with the same 750 Holley Street HP-series carburetor used previously on the 327 and 289. Naturally, both motors were subjected to timing sweeps as well.

First on the pump was the Chevy DZ 302. Rated at 290 hp, the DZ 302 pumped out 356 hp at 6,700 rpm and 333 lb-ft at 4,400 rpm. Where the Boss 302 never reached 325 lb-ft of torque production, the Chevy exceeded 325 lb-ft from 4,000 rpm to 5,200 rpm. The Chevy was certainly the king of the midrange.

Much has been written about the huge ports and valves used on the Boss 302, but the little Boss actually produced more torque at 3,000 rpm than the smaller-port DZ motor. Most important to Ford fans, the Boss 302 produced more ultimate power than the Chevy with peak numbers of 372 hp at 6,800 rpm. The peak torque of 324 lb-ft offered by the Boss was down compared with the DZ, but from 5,800 rpm to 7,000 rpm (and beyond), the Boss was the boss.

Specs At A Glance
&nbsp ’69 DZ 302 ’69 Boss 302
Displacement 302 ci 302 ci
Rated output, horsepower 290 hp at 5,800 290 hp at 5,800
Rated output, torque 290 lb-ft at 4,200 290 lb-ft at 4,300
Bore/stroke 4.0/3.00 4.0/3.00
Compression 11.0:1 10.5:1
2/4 bolt block 4 4
Crank (cast or forged) Forged Forged
Rod length 5.7 5.15
Forged rod Forged Forged
Rod ratio 1.753:1 1.716:1
Head casting No. 186 C9ZE-A
Chamber volume 61 to 64 cc 61 to 64 cc
Valve sizes 2.02/1.60 2.23/1.71
Peak flow rates (intake/exhaust) 210/146 274/176
Screw-in studs Yes Yes
Guideplates Yes Yes
Cam hydraulic/solid Solid Solid
Cam lift (gross) 0.485 0.514
Cam duration (0.050) 254 228
Cam lobe separation 114 114
Intake manifold Dual-plane Dual-plane
Aluminum/iron Aluminum Aluminum
Carb Holley 4150 4V Holley 4150 4V
Carb rating 780 cfm 780 cfm
Tested output, horsepower 356 hp at 6,700 372 hp at 6,800
Tested output, torque 333 lb-ft at 4,400 325 lb-ft at 4,200

cuisinartvette wrote: ↑Mon Oct 30, 2017 12:01 pm Id tend to believe the lower #s posted. Anybody driven a stock 302 or LT-1 back then?
They certainly werent any kind of powerhouse for sure!

cuisinartvette wrote: ↑Mon Oct 30, 2017 12:01 pm Id tend to believe the lower #s posted. Anybody driven a stock 302 or LT-1 back then?
They certainly werent any kind of powerhouse for sure!