68shark

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!!

SuperFast80

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.

QuickVet

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.

68shark

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!!

68shark

Vetteboy....what is your setup? Thanks!!!

tsw71

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.

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.

tsw71

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?

68shark

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.

SuperFast80

All 70-72 LT-1s were solids.

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.

Rowdy Rat

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,

SuperFast80

Stan, thatnks for the clarification on the net figures for 71. I *thought* the LT-1 was higher than 255 but I never found the info.
:cheers:

Easy Mike

"...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.
:)

rainman69

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.

Allan71

I saw a 66 L79 (327/350hp) with a fresh stock rebuild run on a chassis dyno,
and his best was 238 hp at the rear wheels.

68shark

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!!

Chris Fowler

240 rwhp is gonna get you down the track in the mid 14s? Wow! :eek:

SuperFast80

Chris, is your reaction a negative :eek: or a positive :eek: ?

LT1driver

I believe all 70-72 Lt-1s were Solid lifter. :cool:

QuickVet

280HP gets me down the track in 12.9 secs. 240 is more then enought to get there in the 14s. we are talking RWHP here. :D