Bulk vs. Net HP/TQ Question
Thread Starter
Instructor
Joined: Oct 2003
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From: Frederick MD
Bulk vs. Net HP/TQ Question
My question is: If say a '70 Vette was rated at 350hp back then in bulk, would a new crate motor that's rated at 350hp be rated the same? The reason I ask is, I'm looking into crate motors vs. rebuilding the top end on my '72 L48 and trying to figure out costs. That said, a nice new ZZ4 would be a nice fit and possibly a upgrade in hp for even a '70 350/350?
I would like to spend 2k on just the top end of the L48 and get me to 350hp or so (give or take) with iron vortec heads, new cam, manifold and headers. She's only got 78k on her and my parents have had her since '74 and taken real good care of her.
Sorry, I keep going in circles on what to do!
thx,
PLATZIE
I would like to spend 2k on just the top end of the L48 and get me to 350hp or so (give or take) with iron vortec heads, new cam, manifold and headers. She's only got 78k on her and my parents have had her since '74 and taken real good care of her.
Sorry, I keep going in circles on what to do!
thx,
PLATZIE
Drifting
Joined: Feb 2005
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From: San diego ca
Bulk HP?
I think perhaps you are referring to gross HP...only Big blocks have Bullk HP
Anyway.. the answer (to the best of my knowledge) is yes...Crate motors are at best Gross HP numbers, because Net numbers require that full exhaust and accessories be installed, since exhaust and accessories can vary from model to model there isnt any way the crate motors can be rated at net numbers.
I think perhaps you are referring to gross HP...only Big blocks have Bullk HP
Anyway.. the answer (to the best of my knowledge) is yes...Crate motors are at best Gross HP numbers, because Net numbers require that full exhaust and accessories be installed, since exhaust and accessories can vary from model to model there isnt any way the crate motors can be rated at net numbers.
Thread Starter
Instructor
Joined: Oct 2003
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From: Frederick MD
So my L48 was rated at 200hp (net)at the flywheel with exhaust and accessories (water pump, alternator, etc.)?
But a pre-'72 was rated without accessories (gross). So if you were to make the test "apples to apples" the 200hp (net)would be higher if it were tested as (gross)? And a '70 350/350hp would be rated lower if it were rate (net)
It just confuses me as how can I get to 350hp. I keep thinking I have to make up 150hp, but not exactly due to the rating system?
A crate motor is rated gross (since they have no idea what accessories you have)? Makes sence.
So what did my L48 have gross from the factory? As if it were dyno'ed like a crate motor is?
But a pre-'72 was rated without accessories (gross). So if you were to make the test "apples to apples" the 200hp (net)would be higher if it were tested as (gross)? And a '70 350/350hp would be rated lower if it were rate (net)
It just confuses me as how can I get to 350hp. I keep thinking I have to make up 150hp, but not exactly due to the rating system?
A crate motor is rated gross (since they have no idea what accessories you have)? Makes sence.
So what did my L48 have gross from the factory? As if it were dyno'ed like a crate motor is?
Team Owner
Joined: Jul 1999
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From: Huntersville NC
platzie, I thnk you have it right. Your 200 hp (net) 72 would have been rated at 250, or 275, or maybe even 290 hp gross in 1970. Actually it is probably pretty close to the 300 hp engine of 70.
There is an extra confusing feature of crate engines. They are generally rated gross. So the 500 hp 502 bigblock is 500 gross hp. But have you noticed that many original equipment engines are also available as crate engines? The 300 hp LT1 is available as a 300 hp crate engine. Even the new 505 hp LS7 is available as a crate engine. So also notice that these engines retain their factory installed hp rating , which is a net rating. Makes it very hard to compare one engine to the next.
There is an extra confusing feature of crate engines. They are generally rated gross. So the 500 hp 502 bigblock is 500 gross hp. But have you noticed that many original equipment engines are also available as crate engines? The 300 hp LT1 is available as a 300 hp crate engine. Even the new 505 hp LS7 is available as a crate engine. So also notice that these engines retain their factory installed hp rating , which is a net rating. Makes it very hard to compare one engine to the next.
Le Mans Master
Joined: May 2006
Posts: 9,993
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From: League City Tx
I know a stock ZZ4 with a 750 vac sec holley will dyno 270-280 rwhp through a M22 and a ford 9" w/ 4.11s. We did this in my dad's 59'
Thats roughly 20% loss through drivetrain which is about right. I believe crate motors are rated basically gross but through full headers and water pump being ran. The old gross ratings from the 60s-early 70s were TOTAL BS.
Your ZZ4 will waste that stock 350/350hp motor, even assuming that motor was new. We put another ZZ4 in a 68 camaro with headers and the same 750 carb, with a 2800 converter in a 700R4 and 3.73s the car ran 12.80s@104-105. Original L48s would not even come close to that..
Thats roughly 20% loss through drivetrain which is about right. I believe crate motors are rated basically gross but through full headers and water pump being ran. The old gross ratings from the 60s-early 70s were TOTAL BS.
Your ZZ4 will waste that stock 350/350hp motor, even assuming that motor was new. We put another ZZ4 in a 68 camaro with headers and the same 750 carb, with a 2800 converter in a 700R4 and 3.73s the car ran 12.80s@104-105. Original L48s would not even come close to that..
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
MOst crate motor HP rating are plle of BS because none of them will ever see a dyno. THe higher the horsepower the more they can charge so these internet crate engine builders just pull numbers out of their ......
Personally, the GM crate motors are the only ones I would trust as far as HP numbers go and if I had to buy a crate motor I would buy a GM. I too have seen a few ZZ4's on chassis dynos and they vary from 260 -280 RWHP which is in line with the 350HP rating.
Wish I could find the post but I remember someone complaining his ZZ4 was not running too good after only 800 1/4 mile passes
Personally, the GM crate motors are the only ones I would trust as far as HP numbers go and if I had to buy a crate motor I would buy a GM. I too have seen a few ZZ4's on chassis dynos and they vary from 260 -280 RWHP which is in line with the 350HP rating.
Wish I could find the post but I remember someone complaining his ZZ4 was not running too good after only 800 1/4 mile passes
Le Mans Master
Joined: May 2006
Posts: 9,993
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From: League City Tx
Ya people definetly try to sell the "number" more then the product. Just like the turbo kit I have on my busa, Its advertised to make 280 rwhp at 8lbs of boost. Well having the kit for 2 years I am between 260-270rwhp with 12lbs. Vendors know people want hp and are willing to pay for it. They can inflate that number and make more money, less parts/work/development etc.
On another note though, I had a local race shop quote me out a 383 yesterday, carb to pan, dyno tuned, $8633
That was with only a cast crank, I beam steel rods and out of the box Dart Pro 1-215cc. 500-520hp. Those ebay motors are starting to look a little better. LOL
On another note though, I had a local race shop quote me out a 383 yesterday, carb to pan, dyno tuned, $8633
That was with only a cast crank, I beam steel rods and out of the box Dart Pro 1-215cc. 500-520hp. Those ebay motors are starting to look a little better. LOL
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Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Summit is probably not the cheapest to buy a ZZ383 there price is
4789.88 thats a ton less then 8600. you get a brand new 4 bolt
block ( 1 piece rear seal no leaks and designed for a roller ) 4340
chromemoly crank, forged rods, aluminum heads. It makes 425 hp
at only 5400rpm. A little money for a new hydraulic roller that can
pull past 5400 or a soild roller and you are at 500 HP. why mess
with E-bay or machine shops. The old pink chevy rods in my 302
I reved them to 8000 a million times in the 36000 miles that I kept the
car.
4789.88 thats a ton less then 8600. you get a brand new 4 bolt
block ( 1 piece rear seal no leaks and designed for a roller ) 4340
chromemoly crank, forged rods, aluminum heads. It makes 425 hp
at only 5400rpm. A little money for a new hydraulic roller that can
pull past 5400 or a soild roller and you are at 500 HP. why mess
with E-bay or machine shops. The old pink chevy rods in my 302
I reved them to 8000 a million times in the 36000 miles that I kept the
car.
Last edited by Little Mouse; Jun 3, 2006 at 01:12 PM.
Instructor
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there is no way to correlate the pre '72 gross numbers to the new net numbers. in addition to running accs and full exhaust, the barometric pressure and temp baselines were changed for the new net dyno numbers. the only way to get an equivelant is to dyno both motors back to back on the same dyno.
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Originally Posted by Little Mouse
Summit is probably not the cheapest to buy a ZZ383 there price is
4789.88 thats a ton less then 8600. you get a brand new 4 bolt
block ( 1 piece rear seal no leaks and designed for a roller ) 4340
chromemoly crank, forged rods, aluminum heads. It makes 425 hp
at only 5400rpm. A little money for a new hydraulic roller that can
pull past 5400 or a soild roller and you are at 500 HP. why mess
with E-bay or machine shops. The old pink chevy rods in my 302
I reved them to 8000 a million times in the 36000 miles that I kept the
car.
4789.88 thats a ton less then 8600. you get a brand new 4 bolt
block ( 1 piece rear seal no leaks and designed for a roller ) 4340
chromemoly crank, forged rods, aluminum heads. It makes 425 hp
at only 5400rpm. A little money for a new hydraulic roller that can
pull past 5400 or a soild roller and you are at 500 HP. why mess
with E-bay or machine shops. The old pink chevy rods in my 302
I reved them to 8000 a million times in the 36000 miles that I kept the
car.
Ya I have been thinking about the ZZ383 500hp from Sallee chev. Its the ZZ383 shortblock but with AFR 195s, upgraded roller cam, air gap, 750 carb and aircleaner. Its right at $8k after dyno tuning. But I believe the crank is cast and the rods are powder metal.
I could also buy the HT 383 shortblock for under $3k, then buy the AFRs and roller cam and do it all for $6k if I assemble it myself but there would be no warranty or dyno tuning. Several options. Still shopping around. I would like to get out for $6k or less, turn key.
Race Director
Joined: May 2004
Posts: 11,920
Likes: 2
Originally Posted by ajrothm
The old gross ratings from the 60s-early 70s were TOTAL BS.
Your ZZ4 will waste that stock 350/350hp motor, even assuming that motor was new. We put another ZZ4 in a 68 camaro with headers and the same 750 carb, with a 2800 converter in a 700R4 and 3.73s the car ran 12.80s@104-105. Original L48s would not even come close to that..
Your ZZ4 will waste that stock 350/350hp motor, even assuming that motor was new. We put another ZZ4 in a 68 camaro with headers and the same 750 carb, with a 2800 converter in a 700R4 and 3.73s the car ran 12.80s@104-105. Original L48s would not even come close to that..
I believe both engines make 350HP, but.....
.....the newer technology makes 350HP or close to it over a wider band of the RPM range than the 30 year old engine. That is why it has faster 1/4 mile times, not because the HP rating is BS.
I may be wrong.....
