Gross Horsepower LT-5

[Hib Halverson]

The only gen II LT1 which made 300 SAE net was the version in Corvettes and it was available from 1992-1996 with automatics and from 1992-1995 with manuals. That engine never made "377-78" gross at the flywheel. More like 340-350 on a good day.

The Camaro used a less powerful version (275-hp SAE net) of the Gen II LT1 from 1993-1997. There also was an even milder version (260-hp SAE net) used in the Caprice and Impala of the mid-90s.

The Gen II LT1 was, also, not the most powerful "traditional" (Gen 1/Gen II) SBC. That honor goes to the LT4, used in 1996 manuals. It made 330 SAE net about about 370-380-gross hp.

For the record, on SAE net vs. gross power ratings...

Up until the early 1970s car companies rated engines by measuring their torque output with an engine dynamometer than mathmatically deriving the horsepower.

Engines were tested in a manner which had them making the highest possible power output. They were set-up on the dyno with all accessories except the coolant pump removed. They were run with open exhaust. Prior to the early 1960s they used stock exhaust manifolds and after that, racing exhaust headers. The fuel and spark curves were optimized for highest performance. They were run with no exhaust emissions controls. They were run in high-octane, leaded fuel. The intake air temperature was as cold as possible.

In the early 1970s, all the car companies agreed to abide by a new SAE standard which required them to measure "net power". Once again, the ratings were arrived by measuring torque output on an engine dyno, but the engines were run the same way they were configured when installed in a production vehicle. This meant with all accessories (power steering pump, A/C compressor, alternator, etc) installed and operating along with any exhaust emissions controls the production engine may have used. Full stock exhaust systems were installed. The fuel and spark curves were calibrated to production intent. Unleaded pump gas was used. Intake air temp. was 77°F.

The difference in testing methods could amount to 50-hp.

[mrx86]

Hello Mr. Halverson

do you think the 90 LT5 5.7l have 425 gross hp ?

[Hib Halverson]

Originally Posted by mrx86

Hello Mr. Halverson

do you think the 90 LT5 5.7l have 425 gross hp ?

If the engine was run with no accessories other than the coolant pump, optimized fuel and spark cals, optimized cam timing, 70°F IAT, 180° ECT, on higher octane fuel, with headers and open exhaust, yeah...about 425.

[Dynomite]

Originally Posted by Hib Halverson

Up until the early 1970s car companies rated engines by measuring their torque output with an engine dynamometer then mathmatically deriving the horsepower.

Here ya go for those that are not aware of the math

Tech Info - LT5 Horsepower and Torque Calculations

[Hib Halverson]

Originally Posted by Dynomite

Here ya go

Tech Info - LT5 Horsepower and Torque Calculations

Thank you "Dynomite" but I was already aware of the math.

Impressive collection of material you have in that thread on the CF.

[Kevin]

found it.

[scottfab]

Well that's "gross".
sorry, couldn't help it.

Originally Posted by Kevin

found it.

[tpepmeie]

Don't quote me on this, but I read in an old Legend magazine about the development of the LT5, and believe it was stated they were seeing 445 SAE with open headers on the dyno.

[Kevin]

Originally Posted by tpepmeie

Don't quote me on this, but I read in an old Legend magazine about the development of the LT5, and believe it was stated they were seeing 445 SAE with open headers on the dyno.

too late, just quoted you

[zr1mom]

The next gen ZR-1if it wasn't killed off would have been 450hp.