Go Back   Corvette Forum > C3 Corvettes, 1968 - 1982 > C3 General
Sign in using an external account
Register Forgot Password?
Register Search Today's Posts Mark Forums Read FAQ Vendor Directory
Search
C3 General
General C3 Corvette Discussion not covered in Tech Sponsored by
Corvette America

Welcome to Corvetteforum.com!
Welcome to Corvetteforum.com.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join Corvetteforum.com today!


Corvette Store
 
 
C7 Parts & Accessories
C6 Parts & Accessories
C5 Parts & Accessories
C4 Parts & Accessories
C3 Parts & Accessories
C2 Parts & Accessories
C1 Parts & Accessories
Wheels & Tires
Sponsored Ads
 
 
Vendor Directory
  
Reply
 
 
 
 
Thread Tools Search this Thread
Old 02-19-2011, 01:17 AM   #1
LS7Vette
CF Senior Member
 
LS7Vette's Avatar
 
Member Since: May 2009
Default 1973-1974 LS4 454 Gross Horsepower

Does anyone know what the SAE "Gross" Horsepower is on the 73 - 74 LS4 454's? We know what the SAE "Net" Horsepower is, as this is how they rated their cars from 72 on (and why the horsepower dropped so quickly). Just curious what the LS4 would have rated on the old system? Easy for motors like the L48 350 that was around prior to the change.

thanks

LS7Vette is offline   Reply With Quote
Old 02-19-2011, 02:02 AM   #2
Ben Lurkin
CF Senior Member
St. Jude Donor '09
 
Ben Lurkin's Avatar
 
Member Since: Dec 2006
Location: Oquirrh Mountains
Default

Don't know that I've ever seen a gross hp rating for the LS4's. But rest assured, by then, the numbers were indeed gross.

I would hazard a guess they would be in the 340-350 hp range.
Ben Lurkin is offline   Reply With Quote
Old 02-19-2011, 08:27 AM   #3
7T1vette
CF Senior Member
 
7T1vette's Avatar
 
Member Since: Jan 2006
Location: Crossville TN
Default

The LS4 ('72-73) was very similar to the LS5 from 1971. The LS4 compression ratio was a quarter of a point lower and the cam was a little different grind, but that's a pretty small difference. The greatest difference in those two powerplants is the way the HP is rated: LS5 rated at 5400 rpm using SAE "gross" and LS4 rated at 4000 rpm [who are the GM marketing boyz kidding?] and SAE "net" method. If the LS4 were rated similarly to the LS5, it would probably be in the 350+ (SAE gross) at more than 5000 rpm.
7T1vette is offline   Reply With Quote
Old 02-19-2011, 03:22 PM   #4
LS7Vette
CF Senior Member
 
LS7Vette's Avatar
 
Member Since: May 2009
Default

Quote:
Originally Posted by 7T1vette View Post
The LS4 ('72-73) was very similar to the LS5 from 1971. The LS4 compression ratio was a quarter of a point lower and the cam was a little different grind, but that's a pretty small difference. The greatest difference in those two powerplants is the way the HP is rated: LS5 rated at 5400 rpm using SAE "gross" and LS4 rated at 4000 rpm [who are the GM marketing boyz kidding?] and SAE "net" method. If the LS4 were rated similarly to the LS5, it would probably be in the 350+ (SAE gross) at more than 5000 rpm.




I was thinking that this was the range but wanted to hear from you guys. Yes its not as great as the years prior but still not too bad (the change really made it sound worse then it was, atleast this is my opinion). When im done with my car I would like to finish the air cleaner off with a decal and will probably go with 355HP or 360HP. Thanks for your thoughts.

LS7Vette is offline   Reply With Quote
Old 02-19-2011, 05:53 PM   #5
1980 blue L48
CF Senior Member
 
1980 blue L48's Avatar
 
Member Since: Mar 2006
Location: west central INDIANA
Default

I cannot speek of the 73-74 models. I had a 72 SS 454 Chevelle, LS5. It was rated @ 270 net HP. The 71 LS5 was exacally the same motor, It was rated @ 365 gross HP. I think the 73 454 was rated at 5 hp more (275 net)than the 72 Ls5. Hope this helps you, Great Question Too.
1980 blue L48 is offline   Reply With Quote
Old 02-19-2011, 05:59 PM   #6
Rebelrob
CF Senior Member
 
Rebelrob's Avatar
 
Member Since: Jul 2009
Location: Dallas-Fort Worth TX
Default

Hey guys, what is the difference and or definition of Gross vs Net HP rating. I have seen this brought up a few times in the past but forget to ask.
For instance, I know the LS5 454 in the 70 Vette was rated at 390 HP. Is that Gross or Net. I assume the 390 HP rating is at the crank. Same said for the 70 SS Chevelle with the LS6 454 450 HP rating. I always here that these ratings were fudged and actually made a lot more.
Thanks,
Rebelrob is offline   Reply With Quote
Old 02-19-2011, 06:34 PM   #7
7T1vette
CF Senior Member
 
7T1vette's Avatar
 
Member Since: Jan 2006
Location: Crossville TN
Default

SAE "gross" hp is engine horsepower measured at the crank without any parasitic losses for water pump, fan, alternator, etc, etc. SAE "net" hp is the same measurement but including all the engine parasitic losses.
7T1vette is offline   Reply With Quote
Old 02-19-2011, 07:26 PM   #8
Rebelrob
CF Senior Member
 
Rebelrob's Avatar
 
Member Since: Jul 2009
Location: Dallas-Fort Worth TX
Default

Quote:
Originally Posted by 7T1vette View Post
SAE "gross" hp is engine horsepower measured at the crank without any parasitic losses for water pump, fan, alternator, etc, etc. SAE "net" hp is the same measurement but including all the engine parasitic losses.
I see, as mentioned, was the 390 HP 70 LS5 net or gross?
Did they change from Gross to net or vice versa for certain year models?

Good info, thanks,
Rebelrob is offline   Reply With Quote
Old 02-19-2011, 07:27 PM   #9
LS7Vette
CF Senior Member
 
LS7Vette's Avatar
 
Member Since: May 2009
Default

Quote:
Originally Posted by 1980 blue L48 View Post
I cannot speek of the 73-74 models. I had a 72 SS 454 Chevelle, LS5. It was rated @ 270 net HP. The 71 LS5 was exacally the same motor, It was rated @ 365 gross HP. I think the 73 454 was rated at 5 hp more (275 net)than the 72 Ls5. Hope this helps you, Great Question Too.


Thanks for the information, I guess the LS4 was not too much different then the later LS5 motors. Looking at those numbers it could have even been around the 365HP mark.

thanks for all the help guys !

LS7Vette is offline   Reply With Quote
Old 02-19-2011, 07:36 PM   #10
gbvette62
CF Senior Member
 
gbvette62's Avatar
 
Member Since: Oct 2000
Location: Shamong, NJ
Default

Quote:
Originally Posted by Rebelrob View Post

For instance, I know the LS5 454 in the 70 Vette was rated at 390 HP. Is that Gross or Net. I assume the 390 HP rating is at the crank. Same said for the 70 SS Chevelle with the LS6 454 450 HP rating. I always here that these ratings were fudged and actually made a lot more.
Thanks,
For 1970 models, that is a gross rating. All vehicles were gross rated prior to 72. Starting in 72, GM switched to the truer net rating system.

As far as "fudging" the ratings, yes, Chevrolet did that often. Mainly it was done for insurance reasons, or to get around GM corporate edicts about vehicle horsepower levels vs things like vehicle weight or size. In the case of the L-88, I think Chevrolet rated it less than the tri-power (435 vs 430), to discourage the uninitiated from buying the L-88.

Probably the most underated Chevrolet engine (besides the L-88 & ZL-1), was the 67-69 Z28 302, at a mere 290 HP.
gbvette62 is offline   Reply With Quote
Old 02-19-2011, 07:38 PM   #11
gbvette62
CF Senior Member
 
gbvette62's Avatar
 
Member Since: Oct 2000
Location: Shamong, NJ
Default

Quote:
Originally Posted by LS7Vette View Post
Thanks for the information, I guess the LS4 was not too much different then the later LS5 motors. Looking at those numbers it could have even been around the 365HP mark.

thanks for all the help guys !

I think this is a pretty safe bet. The 73-74 454's were probably somewhere in the 355-370 "gross" HP range.
gbvette62 is offline   Reply With Quote
Old 02-19-2011, 07:44 PM   #12
LS7Vette
CF Senior Member
 
LS7Vette's Avatar
 
Member Since: May 2009
Default

Quote:
Originally Posted by Rebelrob View Post
I see, as mentioned, was the 390 HP 70 LS5 net or gross?
Did they change from Gross to net or vice versa for certain year models?

Good info, thanks,


1972 GM cars started SAE "NET" Horsepower, prior to 1972 (1971 and earlier) were SAE "GROSS" Horsepower. Pretty much any decent sounding horsepower rating was SAE "GROSS". The 1970 LS5 454 390HP engine was GROSS horsepower.

LS7Vette is offline   Reply With Quote
Old 02-19-2011, 07:53 PM   #13
LS7Vette
CF Senior Member
 
LS7Vette's Avatar
 
Member Since: May 2009
Default

Quote:
Originally Posted by gbvette62 View Post
For 1970 models, that is a gross rating. All vehicles were gross rated prior to 72. Starting in 72, GM switched to the truer net rating system.

As far as "fudging" the ratings, yes, Chevrolet did that often. Mainly it was done for insurance reasons, or to get around GM corporate edicts about vehicle horsepower levels vs things like vehicle weight or size. In the case of the L-88, I think Chevrolet rated it less than the tri-power (435 vs 430), to discourage the uninitiated from buying the L-88.

Probably the most underated Chevrolet engine (besides the L-88 & ZL-1), was the 67-69 Z28 302, at a mere 290 HP.


Quote:
Originally Posted by gbvette62 View Post
I think this is a pretty safe bet. The 73-74 454's were probably somewhere in the 355-370 "gross" HP range.




I agree what you said about the L88/ZL1 427's along with the Z28 302's. Also thanks for the input on the LS4 HP Rating.

LS7Vette is offline   Reply With Quote
Old 02-19-2011, 08:38 PM   #14
Rebelrob
CF Senior Member
 
Rebelrob's Avatar
 
Member Since: Jul 2009
Location: Dallas-Fort Worth TX
Default

Quote:
Originally Posted by LS7Vette View Post
1972 GM cars started SAE "NET" Horsepower, prior to 1972 (1971 and earlier) were SAE "GROSS" Horsepower. Pretty much any decent sounding horsepower rating was SAE "GROSS". The 1970 LS5 454 390HP engine was GROSS horsepower.

OK, I got it now. I thought I had they changed the ratings type after 1970 or so.
BTW, do you have an LS7 in your Vette? I have an original LS7 block in mine. I am using the original forged crank and rods and oil pan. Everything else is updated though.
Rebelrob is offline   Reply With Quote
Old 02-19-2011, 09:08 PM   #15
LS7Vette
CF Senior Member
 
LS7Vette's Avatar
 
Member Since: May 2009
Default

Quote:
Originally Posted by Rebelrob View Post
OK, I got it now. I thought I had they changed the ratings type after 1970 or so.
BTW, do you have an LS7 in your Vette? I have an original LS7 block in mine. I am using the original forged crank and rods and oil pan. Everything else is updated though.


I do have an original 70's LS7 454 crate motor that had the compression lowered to run on pump gas. It has a BRAKE HP of 636 on the dyno. I dont have it in my Vette but will probably hold onto it to put into a later project.
LS7Vette is offline   Reply With Quote
Old 02-20-2011, 01:41 AM   #16
CCrane72
CF Senior Member
 
CCrane72's Avatar
 
Member Since: Apr 2000
Location: Wichita KS
Send a message via AIM to CCrane72
Default

Quote:
Originally Posted by LS7Vette View Post
Thanks for the information, I guess the LS4 was not too much different then the later LS5 motors. Looking at those numbers it could have even been around the 365HP mark.

thanks for all the help guys !

Just for clarification, the LS4 was a later motor than the LS5. The LS5 was used from 1970 to 1972 and the LS4 from 1973-1974.

cc
__________________
Clifford L. Crane - 1972 Mille Miglia Red Coupe,
Black Leather Deluxe Interior, LS-5, M20,
PS, PB, A/C, all original drivetrain with tank
sticker

2000 Torch Red Convertible, Light Oak Interior,
Light Oak Top, Z51, HUD, 6 Speed, OnStar FMV,
ZO6 Air Box, K&N Filter Charger

BIG SH1T EATING GRIN

CCrane72 is offline   Reply With Quote
Old 02-20-2011, 01:47 AM   #17
hdpete98
CF Senior Member
 
hdpete98's Avatar
 
Member Since: Feb 2002
Location: Carlsbad CA
Send a message via AIM to hdpete98
Default

Quote:
Originally Posted by 7T1vette View Post
The LS4 ('72-73) was very similar to the LS5 from 1971. The LS4 compression ratio was a quarter of a point lower and the cam was a little different grind, but that's a pretty small difference. The greatest difference in those two powerplants is the way the HP is rated: LS5 rated at 5400 rpm using SAE "gross" and LS4 rated at 4000 rpm [who are the GM marketing boyz kidding?] and SAE "net" method. If the LS4 were rated similarly to the LS5, it would probably be in the 350+ (SAE gross) at more than 5000 rpm.
I believe the heads on the 1973-74 BB's were a little lower performance also.
hdpete98 is offline   Reply With Quote
Old 02-20-2011, 02:08 AM   #18
LS7Vette
CF Senior Member
 
LS7Vette's Avatar
 
Member Since: May 2009
Default

Quote:
Originally Posted by CCrane72 View Post
Just for clarification, the LS4 was a later motor than the LS5. The LS5 was used from 1970 to 1972 and the LS4 from 1973-1974.

cc

Yes I am well aware the LS4 was the later motor, just a typo that I didnt catch. I meant to put the earlier LS5. Thanks for catching this........
LS7Vette is offline   Reply With Quote
Old 02-20-2011, 02:09 AM   #19
CCrane72
CF Senior Member
 
CCrane72's Avatar
 
Member Since: Apr 2000
Location: Wichita KS
Send a message via AIM to CCrane72
Default

Quote:
Originally Posted by gbvette62 View Post
I think this is a pretty safe bet. The 73-74 454's were probably somewhere in the 355-370 "gross" HP range.
Technically, if the 1971 and 1972 LS5 were identical, and the 1971 was rated at 365 GHP and the 1972 was rated at 270 NHP and the 1973-74 LS4 was rated at 275 NHP then it follows that the LS4 GHP had to be above 370.

If you do the math 270 / 365 = 74% therefore 74% of 372 = 275.

cc
CCrane72 is offline   Reply With Quote
Old 02-20-2011, 02:14 AM   #20
CCrane72
CF Senior Member
 
CCrane72's Avatar
 
Member Since: Apr 2000
Location: Wichita KS
Send a message via AIM to CCrane72
Default

Quote:
Originally Posted by LS7Vette View Post
Yes I am well aware the LS4 was the later motor, just a typo that I didnt catch. I meant to put the earlier LS5. Thanks for catching this........
Ah you're not the only one in this thread to make a such a typo...7T1vette put the LS4 as a 72-73.

cc
CCrane72 is offline   Reply With Quote
Old 02-20-2011, 02:14 AM
 
Go Back   Corvette Forum > C3 Corvettes, 1968 - 1982 > C3 General
Reload this Page 1973-1974 LS4 454 Gross Horsepower
 
 
 
Reply

Tags
1972, 1973, 1974, 454, 73, corvette, engine, horsepower, hp, ls, ls4, rating, sale, slow, stock


Thread Tools Search this Thread
Search this Thread:

Click for Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
LS2 Certified Horsepower—For LS2 guys Marina Blue C6 Corvette General Discussion 176 02-11-2014 05:47 PM
Horse power rating Tredeclaw C3 Tech/Performance 15 10-30-2013 08:49 PM
72 Gross Horsepower VetteRock89 C3 General 15 08-21-2013 12:43 PM
1970 454/390 Hp Vs 1972 454/270 Hp NMT1957 C3 General 44 10-20-2012 01:51 PM


All times are GMT -4. The time now is 03:20 PM.


Emails & Password Backup