Having never put one of my own cars on a dyno (not kidding- NEVER done it before) I was kind of excited to see what it put down.

It's my 383 with AFR heads, modest cam, low blower compression and Weiand 142 blower pushing 5 PSI into the motor. It's in my 78 Malibu (my Grandmother's old car with 35K original miles!)

Dyno is your typical Dyno-Jet spin-the-big-roller deal. The kind that seem to be everywhere these days. Made 3 runs but with my tall gears getting it to hold top gear when I nailed it from 80 MPH was.... problematic. So I later did it in 2nd gear, despite the fact that I was given stern warnings about running it in anything but 1:1.

The numbers, as you can imagine, were all over the place with the gear selection issue so I basically consider them meaningless but for what it's worth here they are:

HP (take your pick): 367, 389, 407

Torque (take your pick): 412, 464, 526

I never went beyond 6000 RPM, which might have been a bit too soon. HP was flattening out but not totally flat at that point. Torque looked flat as a Kansas wheat field from 3000 to 5200 and then gradually sloping down beyond that.

What are the REAL numbers??? Good question. I'd say, factoring out the shift weirdness and the torque converter "flash" peaks, that it's really around 390HP and 410 Torque to the back tires. BUT HOW CAN IT POSSIBLY BE RIGHT IF THE TORQUE AND HP LINES DON'T CROSS AT 5252 RPMs????? BY DEFINITION THEY MUST!

As many of you know, I have estimated this motor at a "legit" 450 at the crank many times on this board and others. I'd say that's probably about right if you factor out the losses through the converter, trans and rear end. 450 HP Vipers usually lay around 390 to the rollers on this rig. A stock LS-1 usually around 290-300.

One guy layed 370HP to the rollers but with 510 ft/lbs in a N/A 383 with a lumpy cam. I noticed his torque curve started at the peak- his stall RPM of 4500 and then went straight down at a 45* angle until he let out at 6700. So he made 20 fewer HP but 100 more torque. Weird. I attribute that to the high stall converter. He claims to run 12.7 @ 112 on street tires, which would roughly line up to my car's 12.5 @ 115.

Almost all the "race cars" with high stall converters had curves that looked like that. They start and peak the torque curve at stall speed and then a line goign straight down from there.

This is why I HATE dynos. It's hard to know what the numbers really mean. Someone care to explain the inner mysteries of a DynoJet to me?

 

I almost forgot the "big guns".......

One guy layed 750HP to the rollers from a small block of some kind an a really nice S-10 "race truck" with slicks, HUGE exhaust, etc. Whether he was using the nitrous installed on his engine or not I never found out.

My "feel good" moment" came when a guy in ANOTHER S-10 with a small block and "street" appearing exterior and a "10.67" ET still showing in the windows from the previous weekend of racing layed only 460 to the rollers (and was quite upset with it). Made me feel good that a guy with only 70 more HP than I made was running mid-10s.

 

This should make you feel good,
I just went on a Mustang porta Dyno at the track.
My 87 Dynoed only 350 hp / 349 tq at the wheels
and I just got done running 11.27 @ 122.4

Even the Dyno guy was a little puzzled and wanted to get me back on to try again - we think it may have been when the converter locked at 4400 that scewed results.
Most guys with similar HP/weight/mph Dynoed 400+ at the wheels on other dynos.
I may get on a Dyno Jet pretty soon and see whats up.

 

Damon I see you live in Philly ...was this by any chance at today's "Dyno Day" at Gambardella Racing?

 

which afr heads you using

 

The dyno measures horsepower by measuring how
quickly the rollers speed up over a fixed time, and plots that Delta against
the rpm to give you horsepower at specific rpm ranges.

Also remember at the track its not just how much power you have, its how you go about using it. just look at the "stock" cars. A optimum 1/4 mile car is using ALL of its power where street cars are not optimized, They are usually a compromise. (converter,rear gear, trans ratio.......)

 

VEHICLE WEIGHT VS MPH have proven themselves to be very good indicators of HP. MPH wether your vehicle is optimized for either is usually about the same. for instance when my 87 was all stock I went 14.2 @ 94 , switched from 2.73's to 3.73's and went 13.7 @ 94 see what I mean.

 

88IROC350TPI- Yep, that's where I was. It was fun, but not nearly as fun as a day at the track. I was just glad to confirm that in all the years I have been estimating HP from wight and trap speed I have been pretty close. I had estimated my car would put down exactly 390- and I called several people beforehand and told them my estimate the night before so I couldn't "revise history" afterwords. One of those guys is Mark (HeavyChevy) who is on several boards including CamaroZ28.com

87TA- Mustang dynos seem to give low results sometimes for reasons that are beyond me. My brother ran his mild Minirammed 400 on a Mustang dyno once. He got 470 torque and 260 HP. His car had just run 13.0000001 @ 110.5. That's on street tires at a race weight of almost 3900 lbs. No way 260 HP pushed a 3900 lb car to a 110+ MPH trap speed. The dyno operator was similarly puzzled by the results.

Sleepybu- my AFR heads are standard 190s with straight plugs, 74cc chambers.

 

My guess, after looking at several of the printouts from cars with high stalls, is that they are still getting some torque multiplication well beyond stall speed, but less and less as the RPMs climb. Hence, the torque curve goes straight down. The dyno is measuring torque multiplication through the converter as much as it's measuing actual engine output.

On a low-stall converter like mine I'm way outside the RPM range where there's any converter torque multiplication going on. But a car that's got a 4800 stall is probably still getting some "torque help" at 5500 or even beyond.

 

Figured out why the HP and Tq lines don't cross at 5252- the scales on the left and right side of the graph are not numbered the same. Factoring that out.... yep, pretty close.

Thanks to Injuneer on camaroz28.com for pointing that out to me.

 

So I'll be seeing your Malibu down at Atco one of these nights before it closes?

Kat

 

Wow Damon, its nice to finnaly see some numbers, im exited about my soon-to-be blown 383 now! its almost identical, 6" rod 383, 9.5:1, 142 weiand, AFR 195, Commander 950 TBI.

Should be an interesting setup. Just how hard are you spinning that blower to keep 5-6 PSI? This ones still got its "stock" pulley, so i expect about 2-3 PSI hehe...

 

Currently I'm one pulley set away from being maxed-out. I'm running a 7" bottom with the stock 3.08" top. That's 2.28:1. The only higher ratio left is if I swap the top pulley for the smaller 2.95" to get me to a 2.45:1 drive ratio and that's all she wrote for the little 142 (which should get me maybe 6-6.5 PSI).

The Holley 144, being a newer design might have more "headroom" left as far as pulley selection but you'd have to check with Holley about that.

Displacement and cam choice has a HUGE effect on actual boost produced under the blower. The more air the engine can more through itself naturally, the higher you have to spin the blower to make boost.

 

I think the dyno is best used for tuning a motor in a controlled environment. Dyno #'s don't necessarily translate into good (or bad) ETs and mph figures, obviously.

If you can tune a motor to produce more torque and hp on a dyno, it should decrease the time and/or increase the trap speed, but that is the only thing that might be true 95% of the time.

A good case in point is a friend with a blown LT1 97 TA ran out 380 RWHP on the dyno... the car only ran 12.7 at 107.... even with 380 engine hp, it should have run 110+ mph, so the hp isn't giving it the mph or ET it should. But then my Camaro is at least 5mph faster then him and I'd be surprised if it dyno'd 350 RWHP to do it.

 

very good point indeed you can tune a motor and get more power from tuning and find optimum shift points but do not get all hung up on the raw numbers i have no faith in rear engine dynos at all

 

brining this thread back to life because i dont want to start a new one

anyone know any places IN philadelphia perferably the NE where you can get your car dyno'd ? if so where whats the name and how much does it cost?

 

Perkasie, Second street speed. they have a web site. I am sure if all you are looking for is a number and no tuning there is a bunch in jersey.