L79/L46 Dyno information
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 1,160
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From: Ajax Ontario
L79/L46 Dyno information
I'm interesting in hearing from anyone who has had their mostly stock L79 (327/350hp) or L46 (350/350hp) dynoed. Reason is I'm looking to build my 327 to at least the same rear wheel torque and horsepower as the stock motor (preferably more!). Am including the L46 as the published horsepower/torque was similar and there will be more of those on this forum. Just looking to establish good "baseline" information.
My 327 (basically stock, except for the cam below) turned 206 rwhp and 267 torque with a carb that was not (and still is not) setup properly.
Thanks!!
My 327 (basically stock, except for the cam below) turned 206 rwhp and 267 torque with a carb that was not (and still is not) setup properly.
Thanks!!
Race Director
Joined: Aug 1999
Posts: 10,073
Likes: 1
From: Toronto
Re: L79/L46 Dyno information (68shark)
Just playing a numbers game, I think you are dynoing too low.
1. Gross to Net
350hp discounted by 20% - 280hp net.
2. Flywheel to Rear Wheels
280hp discounted by 15% - 238rwhp
Have you run it at the track? With ~240rwp and your setup, it should be mid 14s.
1. Gross to Net
350hp discounted by 20% - 280hp net.
2. Flywheel to Rear Wheels
280hp discounted by 15% - 238rwhp
Have you run it at the track? With ~240rwp and your setup, it should be mid 14s.
Race Director
Joined: Feb 2000
Posts: 12,431
Likes: 1
From: CT
Re: L79/L46 Dyno information (SuperFast80)
superfast: are you sure that you are supposed to take off that much %. i always thought that you only take of 20% once and that was it. why do you take of another 15%?
i dynoed about 280 HP and i know im not really making much more then 340-360HP.
i dynoed about 280 HP and i know im not really making much more then 340-360HP.
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 1,160
Likes: 0
From: Ajax Ontario
Re: L79/L46 Dyno information (SuperFast80)
I wasn't sure....given the factory ratings would have been without things like my ramshorn manifolds that probably don't flow well enough to let the 2.02 stock heads really achieve their potential. That's why I'm wondering if anyone has actually dynoed a fairly stock engine to see what is actually getting to the rear wheels. Bear in mind that the L79 and L46 really only achieve the higher power at the top end, which is precisely where the stock intake/exhaust put a lid on things....
Thanks for the reply!!
Thanks for the reply!!
Drifting
Joined: Mar 2001
Posts: 1,395
Likes: 6
From: Indiana
Re: L79/L46 Dyno information (Vetteboy)
You will need to subtract 15% to get from gross to net hp. Then you must subtract another 15-20% for driveline loss. For the cars that were built after 1971, the rating is net, but before that was gross hp.
Race Director
Joined: Aug 1999
Posts: 10,073
Likes: 1
From: Toronto
Re: L79/L46 Dyno information (tsw71)
Difference between/discount from gross to net:
1971 LT-1: 330 GROSS/255 NET = 22.7% 'loss'
The L79 was 350 GROSS. You need to discount to net THEN to rear wheels.
1971 LT-1: 330 GROSS/255 NET = 22.7% 'loss'
The L79 was 350 GROSS. You need to discount to net THEN to rear wheels.
Drifting
Joined: Mar 2001
Posts: 1,395
Likes: 6
From: Indiana
Re: L79/L46 Dyno information (SuperFast80)
Difference between/discount from gross to net:
1971 LT-1: 330 GROSS/255 NET = 22.7% 'loss'
The L79 was 350 GROSS. You need to discount to net THEN to rear wheels.
1971 LT-1: 330 GROSS/255 NET = 22.7% 'loss'
The L79 was 350 GROSS. You need to discount to net THEN to rear wheels.
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Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 1,160
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From: Ajax Ontario
Re: L79/L46 Dyno information (SuperFast80)
Ok, great replies all!!
If I do the math then, based on Superfast's numbers...350 gross turns into about 270 net. Reducing this amount by say 18% (I know this is another discount factor with many opinions!) would yield 221rwhp. I guess I'm not too far off target...although would love to be somewhere around 230+ at the tires.
If I do the math then, based on Superfast's numbers...350 gross turns into about 270 net. Reducing this amount by say 18% (I know this is another discount factor with many opinions!) would yield 221rwhp. I guess I'm not too far off target...although would love to be somewhere around 230+ at the tires.
Race Director
Joined: Aug 1999
Posts: 10,073
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From: Toronto
Re: L79/L46 Dyno information (tsw71)
Difference between/discount from gross to net:
1971 LT-1: 330 GROSS/255 NET = 22.7% 'loss'
The L79 was 350 GROSS. You need to discount to net THEN to rear wheels.
That's pretty interesting. I would have never thought the difference in gross to net would be that much. Could it be that they went to hyd cam in 72 on the Lt-1 or was that in 71 :confused: Some of my books say that the 71 was hyd, but I have talked to a guy that use to have a 71 LT-1. He said it was solids. Does anyone know the answer to this?
1971 LT-1: 330 GROSS/255 NET = 22.7% 'loss'
The L79 was 350 GROSS. You need to discount to net THEN to rear wheels.
That's pretty interesting. I would have never thought the difference in gross to net would be that much. Could it be that they went to hyd cam in 72 on the Lt-1 or was that in 71 :confused: Some of my books say that the 71 was hyd, but I have talked to a guy that use to have a 71 LT-1. He said it was solids. Does anyone know the answer to this?
In 1971, heads went from 66(or 64)ccs to 76cc to drop compression to 9:1. Also, I know 71-72 pistons were flat top but I *think* 70 had domed tops.
1971 and 1972 are the same engines - just that 72 was rated net.
Safety Car
Joined: Dec 1999
Posts: 3,599
Likes: 837
From: PA
Re: L79/L46 Dyno information (SuperFast80)
Anticipating the change to net horsepower in 1972, Chevrolet rated all 1971 engines with both gross and net horsepower figures. The following figures were published for the 1971 Corvette engines (Gross/Net):
Base - 270hp/210hp
LT-1 - 330hp/275hp
LS-5 - 365hp/285hp
LS-6 - 425hp/325hp
A couple of items worth noting... First, the difference between gross and net horsepower was not a fixed percentage - it varied depending upon the engine. Second, 1971 net horsepower figures are not the same as the 1972 figures so the engines are not entirely the same. I recall reading that this was due primarily due to camshaft phasing and ignition timing.
Regards,
Base - 270hp/210hp
LT-1 - 330hp/275hp
LS-5 - 365hp/285hp
LS-6 - 425hp/325hp
A couple of items worth noting... First, the difference between gross and net horsepower was not a fixed percentage - it varied depending upon the engine. Second, 1971 net horsepower figures are not the same as the 1972 figures so the engines are not entirely the same. I recall reading that this was due primarily due to camshaft phasing and ignition timing.
Regards,
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,481
From: Southbound
Cruise-In II Veteran
Re: L79/L46 Dyno information (tsw71)
"...Could it be that they went to hyd cam in 72 on the Lt-1 or was that in 71 :confused: Some of my books say that the 71 was hyd, but I have talked to a guy that use to have a 71 LT-1. He said it was solids. Does anyone know the answer to this?"
tsw71 -- It's my understanding all LT1s had solid lifters, including the '72s with air.
:)
tsw71 -- It's my understanding all LT1s had solid lifters, including the '72s with air.
:)
Drifting
Joined: Oct 2001
Posts: 1,699
Likes: 1
From: Westampton NJ
Re: L79/L46 Dyno information
I am putting out at least 300 RWHP based on Lars' VeriCom computer. My (unknown internals) L46 is putting out .098 HP/lb which is approximately 300+ RWHP. I'll have to get my car weighed to know exactly what it's putting out.
The changes I know about:
Holley Street Avenger
Weiand 3000 high-rise dual plane intake
Cam swap (specs unknown)
I need to get on a dyno to find out what it says.
The changes I know about:
Holley Street Avenger
Weiand 3000 high-rise dual plane intake
Cam swap (specs unknown)
I need to get on a dyno to find out what it says.
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 1,160
Likes: 0
From: Ajax Ontario
Re: L79/L46 Dyno information (Allan71)
Allan, thanks for the info. This is quite consistent with non dyno feedback from some of the estimations. When you say stock, would that have included stock exhaust manifolds/intake etc?? or was it a stock motor with headers?
Thanks!!
Thanks!!
Team Owner
Joined: Feb 2001
Posts: 49,198
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From: All in!
Cruise-In IV Veteran
St. Jude Donor '03-'10
Re: L79/L46 Dyno information (SuperFast80)
With ~240rwp and your setup, it should be mid 14s.
Race Director
Joined: Feb 2000
Posts: 12,431
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From: CT
Re: L79/L46 Dyno information (Chris Fowler '80)
With ~240rwp and your setup, it should be mid 14s.
240 rwhp is gonna get you down the track in the mid 14s? Wow! :eek:
240 rwhp is gonna get you down the track in the mid 14s? Wow! :eek: