Gross Horsepower LT-5

[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.

[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.

[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 Hib Halverson

And what company put such an engine in a production vehicle?

Disagreement respectfully noted

Ok. If it's in print and GM released the info is should be a simple task for you to post some facts to support your disagreement or at least direct me to some location on the web where I can read those facts.

1995 Firehawk, LT1 rated at 315 sae net hp.

1994 Chevrolet Power-The Official Factory Performance Guide" 1994 General Motors Corporation Page 10

There is an actual reference to an actual gross number for the GEN II LT1, but I cant locate it at this time.

peace
Hog

[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

[mike100]

From 5 minutes of looking into it, 1997 camaro SS and Firebird WS6 LT1's were rated at 305hp. regular Z28 models were 285hp for 96,97 and 275 for the earlier years btw.

The SLP firehawk and SLP SS Camaro got the LT4 in 97 just before the switch tho the LS1 on the f-body.

[Paul Workman]

Originally Posted by Hog

1995 Firehawk, LT1 rated at 315 sae net hp.

peace
Hog

Yeah, I ran across one of those driven by a couple gals. It was right after I had finished my top end porting on the Z (somewhere in the 400 at the wheels area) The Firehawk was impressive, and I guess the gals thought they were picking on some ordinary C4, but they were entirely overwhelmed by the Z.

But, back on topic, there's gross and SAE net and RWHP and RWHP "under the curve". JMO, but HP at the wheels, where the rubber meets the road is the only meaningful measurement. Everything else is just so much hot water generated that means nothing, far as performance goes, methinks.

P.

[tpepmeie]

Ok I found the article. March/April 1998 Legend magazine. Page 14 is an article by Graham describing the 93MY changes.

"405 bhp was realized in GM Test 1 spec, which means with full vehicle inlet and exhaust system,

in GM Test 20 form, ie., dyno headers and no inlet restriction the 1993MY engine produced 445 bhp with optimized spark and fuel (LBT/MBT)."

So we have two different GM test specifications, with a 40bhp difference with headers and optimized tuning. What I don't know is what atmospheric correction factor GM uses for each of these tests. I believe it is probably 77F / 990mbar (SAE J1349) conditions, but I can't certain.

Doesn't really answer the original poster's question, but offers some insight into the difference with open headers/intake.

[efnfast]

I must agree with Paul, all this manipulation of numbers is meaningless. As Paul said, "where the rubber meets the road". SAE corrected or not, me and the guy next to me are breathing the same air when the right foot hits the floor.

[tpepmeie]

Originally Posted by efnfast

I must agree with Paul, all this manipulation of numbers is meaningless.

You clearly mean that it is all *meaningless* to you, right? If it were meaningless to everyone, we wouldnt have a lengthy thread here, right?