CCrane65

Does anyone know if there was ever a dyno graph ever published with the horsepower and torque curves on it for the 72 LS5?

Since horsepower was listed as 270@4000, I would like to see what the maximum was at 5300. Same for torque.

cc

72ragtop

Had my stock 72 rear wheel dyno'd on dynojet , I dont have a scanner or i'd scan the dyno sheet.
This is Rear Wheel HP on a stock 72-454 with auto and 3.08's
sheet starting recording at 3250 rpm

3300 rpm 200hp 305 tq
3500 rpm 205 hp 325 tq
3750 rpm 230 hp 326 tq ** tq peaked 325.98 at 3600 rpms **
4000 rpm 235 hp 305 tq ** hp peaked 235.90 at 4200 rpms **
4250 rpm 235 hp 285 tq
4500 rpm 230 hp 270 tq
4750 rpm 220 hp 245 tq
5000 rpm 200 hp 210 tq

Tq starting falling off at 3750 steady down to 210 tq at 5000 rpm
Hp stayed level 3750 - 4500 rpm and dropped to 200 at 5000 rpm

Peak tq was 326 between 3500-3800
Peak Hp was 236. And was steady between 3750-4500

CCrane65

Makes me realize I have no idea how Chevrolet measured horse power and torque but I'll bet it was on a stand and not a chassis dyno.

cc

DRIVESHAFT

It was absolutely for sure not on a chasis dyno.
Those only got popular somewhat recently, and car manufacturers still dont use them for advertised hp.

71coupe454

Whats that say about all the stories that GM under estimated all the HP ratings to get over on insurance companies? I always wondered how stock rebuilt motors would test now with out marketing involved compared to GM's advertised ratings in the late 60's-early 70's.

danthony

I know mine does not feel very strong at 5300, I never really take there. I don't think we have an L-88 type situation going on with the low compression LS-5.

CCrane65

Yeah, I'm thinking when it's time to rebuild it, she may need a little higher compression and maybe a few LS-6 parts like intake, heads, pistons.

cc

TheSkunkWorks

When the time comes, if you go to the trouble and expense to dyno it, I might suggest having results corrected to SAE standard reference conditions (such as J1349: 77*F, 29.235" Hg / 990mb, 0% relative humidity), as such will relate more accurately.


TSW

Ganey

+ CAM !


Yes, they were not rated on a chassis dyno.!

Ganey

PS Even into the later 70s, calling an insurance co. typically got this response "We don't insure Corvettes!"

I got one at a young age.

CCrane65

When I had my 65 roadster I was with State Farm and they put a "fiberglass surcharge" on it.

cc

CCrane65

We have one dyno here in Wichita that I am aware of and I don't know much about them. But if I ever get to one of the large Corvette meets, I hear they have vendors who bring them. Maybe then I can get it done.

cc

72ragtop

Cliff
Like everyone has said. cars were run on engine stands back in the day. I figured i see all the locals with C5/C6's doing work and dyno'ing their cars all the time. So one weekend had mine done as i was curious to see the net ratings vs. advertised flywheel gross. I was being told expect a 15-20 percent reduction on HP.
Price wise i've seen shops do group specials. $35-$50 per run. Nice to go see some 500 RWH cars on the dyno. Some turbo trucks put out some nice numbers also.
Ken

CCrane65

Yeah, I'd always heard to allow 15-20% drive train loss also but to go from 390 foot pounds to 245 foot pounds is quite a bit more than 15-20%. In fact my calculator says 37%.

Then there's the 455 foot pounds from the data plate. They must have let a hippie slip into the design department to work on that one.
Actually, I'll bet it was one of the design staff's kids who erased the 2 at the beginning and added a 5 at the end so 245 became 455.

cc

Frogday

My butt dyno is sensitive enough to tell me my stock LS5 wouldn't stand much of a chance even against a C4.

CCrane65

My car has plenty of pull after it crawls out of the hole. I think replacing the 3.08:1 gears with 3.70:1 would help that a bunch and move the butt dyno readings up too.

cc