Re: "Legendary Smallblock Shootout"
If you never operate your engine below 3000 RPM there may be some useful results, here.
There is not enough detailed information presented to make any firm conclusions, but I'll offer the following observations:
1. The bit of head flow data in the photo indicates that the heads were not "massaged" other than valve seating, and given what appears to be OE flow, the power numbers are high compared to the lab dyno test data I have for unmassaged heads, but close to what I have for massaged heads. Magazine tests always seem to produce higher results than the database I have of customer tests on similarly configured engines. Go figure!
For example, a "327 LT-1" with well massaaged heads pulled about 360 HP@ 6500 SAE gross on a lab dyno with manifolds. Headers were also tested and they improved peak torque by about 8 percent, but only improved peak power by less than 2 percent relative to the OE 2.5" manifolds. In the car with the vehicle exhaust system the differences between headers and manifolds would probably be narrower.
A nearly identical "327 LT-1" produced 278 SAE corrected RWHP @ 6500. With a 0.85 driveline efficiency factor, estimated SAE net at the flywheel is about 327, and based on data I have accumulated, my estimate for the net/gross ratio on 327s with 2.5" OE exhaust and a clutch fan is 0.89, so 327 net is 367 gross. For these empirically developed conversion factors, the correlation between these two engines is very good. About 40 percent of the net/gross conversion factor is due to the different air density correction and the rest is the effect of exhaust system and front end accessory parasitic loss.
2. It appears that the same manifold/carb was used for all testing. If this was the case, then the 302 and 327 should produce about the same peak power at about the same mean piston speed, which appears to be the case. (I have discussed this "similar engines" situation - everything the same except stroke - many times.)
As is the usual case for typical dyno testing, performance data for the rev range where typical road engines spend 90-99 percent of their time - off idle to 3-4K revs is ignored, and the differences in this low/medium rev range would be much more dramatic than in the upper 1500 RPM range where each of these engines make their best average power; 1500 is the approximate range that OE gear box spacing (except 3-4 on the WR) keeps the engine in when shifting somewhere between 6000 and 7000. If you shift at 6000 revs drop to about 4600. Shift at 7000 and they drop to about 5400. One of the most useful results of dyno testing is finding this "power sweetspot".
The other conclusion you can draw is that for two engines identical other than stroke, the short stroke engine will need shorter gears and, perhaps, more gears to equal the acceleration and top speed performance of the longer stroke engine. This is generally illustrated in the old adage: There is no substitute for displacment.
Duke
If you never operate your engine below 3000 RPM there may be some useful results, here.
There is not enough detailed information presented to make any firm conclusions, but I'll offer the following observations:
1. The bit of head flow data in the photo indicates that the heads were not "massaged" other than valve seating, and given what appears to be OE flow, the power numbers are high compared to the lab dyno test data I have for unmassaged heads, but close to what I have for massaged heads. Magazine tests always seem to produce higher results than the database I have of customer tests on similarly configured engines. Go figure!
For example, a "327 LT-1" with well massaaged heads pulled about 360 HP@ 6500 SAE gross on a lab dyno with manifolds. Headers were also tested and they improved peak torque by about 8 percent, but only improved peak power by less than 2 percent relative to the OE 2.5" manifolds. In the car with the vehicle exhaust system the differences between headers and manifolds would probably be narrower.
A nearly identical "327 LT-1" produced 278 SAE corrected RWHP @ 6500. With a 0.85 driveline efficiency factor, estimated SAE net at the flywheel is about 327, and based on data I have accumulated, my estimate for the net/gross ratio on 327s with 2.5" OE exhaust and a clutch fan is 0.89, so 327 net is 367 gross. For these empirically developed conversion factors, the correlation between these two engines is very good. About 40 percent of the net/gross conversion factor is due to the different air density correction and the rest is the effect of exhaust system and front end accessory parasitic loss.
2. It appears that the same manifold/carb was used for all testing. If this was the case, then the 302 and 327 should produce about the same peak power at about the same mean piston speed, which appears to be the case. (I have discussed this "similar engines" situation - everything the same except stroke - many times.)
As is the usual case for typical dyno testing, performance data for the rev range where typical road engines spend 90-99 percent of their time - off idle to 3-4K revs is ignored, and the differences in this low/medium rev range would be much more dramatic than in the upper 1500 RPM range where each of these engines make their best average power; 1500 is the approximate range that OE gear box spacing (except 3-4 on the WR) keeps the engine in when shifting somewhere between 6000 and 7000. If you shift at 6000 revs drop to about 4600. Shift at 7000 and they drop to about 5400. One of the most useful results of dyno testing is finding this "power sweetspot".
The other conclusion you can draw is that for two engines identical other than stroke, the short stroke engine will need shorter gears and, perhaps, more gears to equal the acceleration and top speed performance of the longer stroke engine. This is generally illustrated in the old adage: There is no substitute for displacment.
Duke
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