Gross Horsepower LT-5

[Hib Halverson]

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.

Actually, if that was in the old Legend magazine, whatever article that was must have been talking about the Record Run engine which, slightly modified, made 440-hp.

Also, no engine could make "445 SAE with open headers" because the SAE test standard mandates a full exhaust system.

Stock LT5s made 375-hp SAE net or 425-hp gross with open exhaust.

Originally Posted by zr1mom

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

The so called "third generation LT5" which would have gone to production for 1995 had additional improvements, including variable valve timing, and would have been rated at 475-hp SAE net. The development program which was that engine ended when the ZR-1 was killed.

[XfireZ51]

Didn't SAE net rating start in 1971? I believe that was part of the reason, along w lower compression, that the 71 LT-1 was rated at 330 v 370hp for the '70 LT-1.

[Hib Halverson]

Originally Posted by XfireZ51

Didn't SAE net rating start in 1971? I believe that was part of the reason, along w lower compression, that the 71 LT-1 was rated at 330 v 370hp for the '70 LT-1.

Could be wrong, but my understanding is that GM began using the SAE-net rating system for 1972.

I remember that it was low compression for unleaded gas in 1971 and SAE-net in 1972.

[Hog]

Originally Posted by XfireZ51

Didn't SAE net rating start in 1971? I believe that was part of the reason, along w lower compression, that the 71 LT-1 was rated at 330 v 370hp for the '70 LT-1.

The 1970 LT-1 was rated at 370 gross hp.
The 1971 LT-1 was rated at 330 gross hp(less cr)
The 1972 LT-1 was rated at 255 SAE net hp. (little difference to the 71 LT-1).

The net rating started in 1972, which is why the 1971 330 gross rating now became 255 net hp in 1972 without major engine differences. The reason for the compression drop was the upcomming switch from leaded fuel to unleaded fuel. Leaded fuel is a high temp lubricant and antiknock agent. Using unleaded fuels in a head without hardened seats will cause the valve seat to recess very quickly. Catalytic converters came in 1975 and lead will coat cats rendering them useless. So GM had to start making changes in their engines to get ready for the upcomming emissions regulations.

So the Vortec 350 that is in my 96-98 GM trucks which are rated at 255 sae net hp @ 4600rpm and 330 lb/ft at 2800 rpm is actually matching the output of the 1971-72 LT-1.

peace
Hog

[tpepmeie]

Originally Posted by Hib Halverson

Actually, if that was in the old Legend magazine, whatever article that was must have been talking about the Record Run engine which, slightly modified, made 440-hp.

Also, no engine could make "445 SAE with open headers" because the SAE test standard mandates a full exhaust system.

Stock LT5s made 375-hp SAE net or 425-hp gross with open exhaust.



The so called "third generation LT5" which would have gone to production for 1995 had additional improvements, including variable valve timing, and would have been rated at 475-hp SAE net. The development program which was that engine ended when the ZR-1 was killed.

Gawd Hib you are full of yourself. I shall dig through my stack of magazines tonight to rebutt you. No, on second thought I have better things to do with my life.