Gross Horsepower LT-5
 

Hello Guys.

a question:

OK the Stock 90 ZR-1 have 375 HP.
And the "Gross Horsepower" Rating is for this Engine ???
440 HP or less ?


What do you think?

Bye
Mrx86.

Re: Gross Horsepower LT-5
 

there's a section in the drivers book and the coffee table book, I think, that talks about this. I don't have either with me right now or i'd be able to answer you. if you have the two books i'm talking about, they're in the owners kit, you can find them yourself. i'm sure someone else can get it to you before I do which will be tomorrow at the earliest

Re: Gross Horsepower LT-5
 

Are you asking about not SAE CORRECTED? Or gross without accessories?

Re: Gross Horsepower LT-5
 

I believe the answer he's looking for is without accessories. If memory serves it's 425 but I'll have to double check.

Re: Gross Horsepower LT-5
 

I have the coffee table book here, but I can't find gross numbers (although I may have missed it). It does state 375 SAE net on a number of pages though :)

Re: Gross Horsepower LT-5
 

The SAE numbers seem like a much more practical measure. There was so much going on gaming the system to cheat the insurance companies..or maybe the other way around faking the funk to lure customers with overrated claims.

the 1970 hemi was rated at 425 hp at 5000 rpm (officially), but I heard it made 470hp if you revved it out to 6000 rpm...and probably more than 500 if you put headers on it.

Re: Gross Horsepower LT-5
 

Our 375 and then 405 ratings are what used to be called "gross" hp back in the old days of the 60's & early 70's.

The OE's used to rate each type engine without any accessories in a test cell. That was the number they gave to the world at large as how much hp the motor produced. I guess the insurance industry used that number for the risk level of a car???? Anyway there was much skullduggery going on. In 1971 the SAE folks wanted some accessories to be included; by '72 it was agreed that a motor should be tested with all it's accessories in place and with the exhaust manifolds and later CATs in place ( I'm 100% sure about the CATs ) and that hp figure would be called SAE corrected net hp. They were trying to get as close to "as installed" as they could to give a hp figure. I figure that would include W/P, Alt, A.I.R. pump, P/S, exh manifolds, all emissions' controls and programing. Anyway, since 72 all engines are tested in this formula (?) to give apples to apples numbers and no funny stuff.

As an example, since I had one of these, the 70 C3 LT-1 yielded 370 hp @ 4800 rpm; a 71 C3 LT-1 yielded 330 hp @ 4800 rpm; a 72 C3 LT-1 = 255 hp @ same rpm. The only running mechanical changes were larger combustion chamber heads for 71 & 72 vs 70; cams were made a bit milder as time went on proly due to CC size, 64 cc chambers in 70 to 76 cc chambers in 71 & 72. The blocks, pistons & rings & rods and piston top ring to deck measurement at TDC remained the same. Im my 72's owners manual the graphs for hp and T/Q stopped at 4800 rpm unlike our graphs that run out to the real peak rpm points. So I'm guessing that the SAE also eventually required the OE's not play games with the rpm that they used to get a max reading.

:cheers:
Tom

Re: Gross Horsepower LT-5
 

tom,
I don't believe that's true. http://ateupwithmotor.com/automotive...orsepower.html

i used to know what the gross rating was since I hung around with classic muscle car guys but I've long since forgot it

Re: Gross Horsepower LT-5
 

OK

how much have the "90 ZR-1" SAE Gross Horsepower
without accessories now ???


90 LT-5 ZR-1 5.7L Stock:
SAE NET Horsepoer = 375HP
SAE GROSS Horsepower (without accessories) = "unknown spirit"


some specialists say 440 HP.

has not measured?
(measurement method as in 60 years...)



Bye

Re: Gross Horsepower LT-5
 

Gross hp
SAE net 70's
SAE "Certified" Power started with the LS7 in 2006 which is rated at 505hp/470 lb/ft SAE Certified using the J2723 which is a voluntary 3rd party rating in addition to the J1349 rating of Aug 2004.

http://www.sae.org/certifiedpower/details.htm

The 375hp and 405 hp LT5's are rated using SAE net hp, certainly not gross rating methods.

The 92-97 LT1 5.7 had a net raing of 300hp, which was about 377-78 gross hp which made it the highest output SBC in history eclipsing the 375hp fuelie 327 and 370hp LT-1 350.

peace
Hog

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

Hello Mr. Halverson

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

Re: Gross Horsepower LT-5
 

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.

LT5 Horsepower and Torque Calculations
 

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

Tech Info - LT5 Horsepower and Torque Calculations

Re: 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.

Re: Gross Horsepower LT-5
 

found it.

http://i190.photobucket.com/albums/z...pa/photo-2.jpg

Re: Gross Horsepower LT-5
 

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

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

too late, just quoted you

Re: Gross Horsepower LT-5
 

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

Re: Gross Horsepower LT-5
 

Thank you.....I appreciate and study ALL of your technical posts and technical references (very well written) :handshak:

I am aware of your familiarity with the math and technology. I provided the information sources (same in this post) for those that are not as familiar and have an interest in additional technical information regarding Horsepower :thumbsup:

Here is some more technical information directly related to LT5 Horsepower. All of which is updated on a continual bases with updates noted at the bottom of each post. ;)

This includes the Signature -Solutions- with updates noted at the bottom of each post.

Tech Info - LT5 Modifications/Rebuild Tricks (500+hp) (100 Posts)

Tech Info - LT5 Eliminated Systems
Tech Info - LT5 Added Systems
Tech Info - LT5 New Rebuild Issues (Lifters and Camshafts)
Tech Info - LT5 Timing Chain Calculations
Tech Info - LT5/ZR-1 Technical Calculations

http://i287.photobucket.com/albums/l...T5/Blingzz.jpg

Re: Gross Horsepower LT-5
 

Nice catch ... where is this page from?

Re: Gross Horsepower LT-5
 

the small, hard bound, "drivers book" that came in the owners kit.

Re: Gross Horsepower LT-5
 

i thought i'd heard closer to 500

Re: Gross Horsepower LT-5
 

Obviously I was referring to the 92-96 Y-body Vette LT1, although there isnt much different power productionwise between the F-Body and Y-body LT1(cam, exhaust, air intakes). There were 315hp F-body LT1 engines with optional intakes and exhausts.

You are correct about the LT4 being the highest output GEN I/II engine. The material I was referencing was written in 1994 hence my oversite of the LT4 which was used in the 96 Vettes and the 135 1997 Camaro/Firebirds(which actually use a stock LT1 F-body calibration, for emissions, without the Vette LT4's 6412 rpm rev limit, along with extrude-honed stainless steel exhaust manifolds and balanced and blueprinted longblocks UNLIKE the stock 1996 Y-body LT4's). The LT4 was a great engine, LS1 power in the standard 4" x 3.48" GEN I/II package. 1997 LT4 SS Camaro runs high 12's same as a a stock LS1 equipped 98-02 Camaro, both equipped with the T-56 trans of course.

I respectfully disagree about your LT1 hp assertions.
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 92-97 LT1 Y-body engine outputs more gross hp than any GEN I engine, even the 70's 370 hp LT-1 and the 60's 375 gross hp L84. This fact is in print by sources including GM.

To complete the GEN II story, yes, the LT1 was used in the 94-96 B-body(Caprice/Wagon/9C1 Police PAckage,Impala SS, Buick Roadmaster/Wagon), 94-96 Cadillac Fleetwood. Although these LT1's used iron heads which flow slightly more than the aluminum Y/Fbody cousins. All 94-96 iron headed LT1's used the same 191/196 0.412"/.428" 111ºLSA which is also shared by the 1996-2002 L30 Vortec 305 230hp at 4600rpm/280 lb/ft torque at 2800rpm, and 96-2003 L31 Vortec 350 with 255 sae net hp at 4600rpm/330 lb/ft torque at 4600rpm.
This same roller cam is also used in the other "baby" GEN II engine, the 94-96 4.3l 265 cid V8 RPO L99 that made 200 sae net hp and 245 lb/ft torque used in the B bodies. This engine got better fuel economy than the 5.7 LT1. The 4.3 V8 uses a 3" stroke crank and special length 5.94" PM rods coupled with 3.736" Vortec L30 305 pistons to get to the 265 cid. If this 3" 2 piece RMS crank is dropped in any 1 piece RMS 4" bore block and you now have a more modern 5.0 302 SBC engine. GMPP built a GEN II 302 that made over 420hp with 7000rpm capability.



peace
Hog

Re: Gross Horsepower LT-5
 

OK

The 90 ZR-1 LT5 / 5.7L have Stock SAE Gross 425HP and 375HP net.

The 1968 Camaro ZL-1 7L Stock have SAE Gross 425HP and 376HP net.

The 1971 Dodge Challenger 7L HEMI have SAE Gross 425HP and 350HP net.

The 1968 Ford Mustang 7L GT500KR have SAE Gross 400HP and ??? HP net.



properly ?

Mrx86

Re: Gross Horsepower LT-5
 

http://img543.imageshack.us/img543/1682/54037937.jpg

Re: Gross Horsepower LT-5
 

Interesting stuff , Thanks guys !!!!!

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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

Re: Gross Horsepower LT-5
 

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

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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.

Re: Gross Horsepower LT-5
 

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?