LS7Vette

I like the math !!!!!!!!!!!!!!

LancePearson

I was curious about the difference between hp ratings since a friend owned a a '67 small block 350 and I own a 76 small block 350. I've grown accustomed to thinking mine is slow by all standards and lots less powerful. however, it turns out that with minor differences that may not be so true except when you compare it to 427 or 454 stock engine or 383 stroker variants. I looked it up another way on a site that lists specifications by year and discovered that in 0-60 times, 0-100 times and quarter mile times and speeds that my '76 was actually faster. Neither was quick like a 427, of course, but small block to small block lower compression to higher compression the facts suggest that the gross or flywheel to rear wheel as I've been told losses were really pretty great. After changing the 2-1-2 exhaust to straight duals and flowmasters my '76 seems to have fairly adequate power now and very uniform through the gears. No drag car by a long shot but if I want that then I can buy some form of a big block or turn this into a 383 by going inside the moter. It suits me as is but I'd guess the losses on the L48 from the ratings were really something like 75 hp or maybe even 90 hp based on times for similarly equipped 67 and 76 cars. Not what I expected to find at all. Again...neither was going to be a drag car with the small stock block.

PRNDL

Didn't Chevrolet provide both gross and net numbers for the 1971 model year? I seem to remember reading somewhere that the mighty 425 hp LS-6 (gross) was 300 hp net.

LancePearson

I have a suzuki burgman an650 bike which has a 50 hp at the ending motor which ends up through a gear drive and cvt trans. to be around 35 at the rear wheel which would be about a 1/3 loss due to mechanical fiction and mass between engine and tire. The Vettes have to drive a transmission if manual which is a bunch of rather small gears then turn a drive shaft then a differential full of gears then two more drive shafts then overcome the friction of the bearings in the two rear wheels as well so I'd say losing maybe 25% to mechanical losses of forces isn't out of the question. In my case that would make a 300 hp flywheel a 225 hp at the rwheel. A 425 hp could be 425 down to 317 hp at the rw on the same basis. Probably a decent factual thread about all this somewhere.

zwede

Yes, in 1971 both ratings were available. My LS5 was 365 gross and 280 NET (or maybe 285, can't recall).

Remember that the Gross rating was not only without accessories, but also allowed dyno headers, bigger carb, and a recurved distributor (explaining the rather large difference).

I think the LS6 was 325 NET.

1980 blue L48

An LS6 450 hp gross, in 1970, 325 net that seems low ? All I can remember about my 72 LS5 in my Chevelle, when I was 18. It had 3.31 gear, and its torque was all instant, like just off idle, then it felt like it was going to rip the bolts out from under the seats, when I mashed the throttle, my high school buddies still talk about that torque monster. That was 1977-79. I would love to feel the power of the new ZR-1, as a comparison, or even the 430 HP base model.

LS7Vette

The LS6 talked about here is the 1971 Corvette LS6 that had a "GROSS" HP of 425.

LS7Vette

[QUOTE=zwede;1576845903]Yes, in 1971 both ratings were available. My LS5 was 365 gross and 280 NET (or maybe 285, can't recall).

QUOTE]


It should be 270HP "NET" according to GM 1972 Corvette option list. Same LS5 motor.

CCrane65

[QUOTE=LS7Vette;1576850313]Well, you know all of the manufacturers played fast and loose with the hp numbers. Still do to a much lesser degree.

cc

llabesab7

Does it really matter?

zwede

3 years later? Probably not.

llabesab7

[QUOTE=zwede;1587245855]3 years later? Probably not

Better late than never I always say

early shark

The '71 and '72 LS-5 engines were not identical, there were calibration changes in the carburetor and distributor, the GM Official gross horsepower rating was 350 hp, down an additional 15 hp from the 1971 rating. The 1971 LS-5 net hp rating was 285 hp versus 1972 at 270 hp. With the additional changes made in 1973 & 1974 the 454 engines had to be downgraded even further to LS-4.

4 speed

so has any one dyno'd a 73 454 either engine or chasis, real numbers not probably, maybe or could be?

4 speed

I remember reading an artical years ago that dyno'd a ZL-1 and 302 , they were like 650hp and 490 hp

CVO2FIXUP

This chart was forwarded to me by one of the members as I am a total newbie when it comes to classic cars. Thia chart made things a heck of a lot easier for me.

http://corvettec3.ca/engines.htm

RickyDee

The 454 was in the corvette from 1970 to 1974?
From 1970 to 1972 called the LS5 was rated in gross hp at 5400 rpm?
From 1973 to 1974 called the LS4 was rated in net hp a 4000 rpm?
If the LS4 was rated in gross hp like the LS5 it would be at 365 hp?

zwede

Yes

No.

70 LS5: 390 gross
71 LS5: 365 gross, 285 net
72 LS5: 270 net
73 LS5: 275 net
74 LS4: 270 net

So the LS4 would probably be 350 gross.

As a data point about underrated engines:

My '71 LS5 was almost 100% stock at one time. The only mod was an old Comp Cams hydraulic flat tappet cam, 219/229 (barely more than stock). With a 4-speed manual it put down 250 rear-wheel hp on a dynojet. It ran a best of a 14.1@101 mph 1/4 mile. Pretty weak for "365 hp".

A very few engines were underrated for various reasons. The vast majority had inflated power numbers.

68/70Vette

Here in California, there's no smog inspection for engines prior to 1976. Don't know about your state. Without smog restrictions, you can get really big horsepower out of a 454. 550 flywheel HP is pretty do-able. For large HP, go to rectangular port heads. Also, the all cast iron BB's are kinda pigs...get aluminum heads, aluminum intake manifold, aluminum water pump and get the front end weight down.
.............
About the heads...I know that there's a lot of recommendation for oval ports for street use. I've never had any problem with rectangular ports and I know they breath better.

Tom73

How do these old threads keep getting revitalized?

This one started in Feb 2011, came back in Nov 2014, and is now back in Apr 2015.