Yes it could. I mean, you're not asking much out of a 340. 1.07 hp/ci? The last 340 +.030 we did was 9.37:1 compression with J heads that flowed 256 cfm @ .550". 6-bbl intake and a solid flat tappet cam 234/238, .523/.538, 106 LSA in at 104 ICL. It peaked at 1.174 lb-ft/ci, 1.226 hp/ci and was making 404 HP @ 5,700 rpm. It went into a 1970 T/A Challenger and has maybe 10 miles on the engine. Been locked in a metal shed for a year(?) now. Will be a heck of a barn find some day.
340 on dyno video, whats your opinion
- Thread starter duster360
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Exactly, head work would be the key to making power. Ain't getting there with the 225cfm dogs that stall out at 450 lift. 
I looked at those videos of Tony's before and thought they were high but without knowing exactly whats inside those motors? Anyhow dyno no's are just that. Some "real" track no's for my '71 340 Cuda as I bought it before the mods I did>
Approx 3580lbs@line, ran alternator, mech w-pump, stock 2.02's, .484 purple, intake, 750DP, small hdrs, 3.55's, B&M super holeshot, 8x26 slicks, best was 13.29@101+, that = 301fwhp
With mods.....same stock heads, .590" purple solid, H/strip Dom int., 2" open spacer, 850DP, 1.3/4" race hdrs, 4.30's, T/A 4200 stall, 10x28's, best on that was 12.41@108 = 370fwhp, max rpm 6100........take the alternator and mech w/pump off, and I guess that would show 400+ on a dyno.
Approx 3580lbs@line, ran alternator, mech w-pump, stock 2.02's, .484 purple, intake, 750DP, small hdrs, 3.55's, B&M super holeshot, 8x26 slicks, best was 13.29@101+, that = 301fwhp
With mods.....same stock heads, .590" purple solid, H/strip Dom int., 2" open spacer, 850DP, 1.3/4" race hdrs, 4.30's, T/A 4200 stall, 10x28's, best on that was 12.41@108 = 370fwhp, max rpm 6100........take the alternator and mech w/pump off, and I guess that would show 400+ on a dyno.
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Sounds like a slow revving engine. Of course, the dyno was holding it back.
The programmer's must start with stock specs. I ran my 273 and it came up within a couple ponies of the 235 horse spec. If you guess on the rest of the combo It's exactly that. A guess.Thanks Toolman.... some of the numbers are funny like that old Dyno Derby 340 with a XE268H, stock heads popping 390+ hp... sure it does... Not a fricken real world chance it runs anywhere close to those numbers at the track! Maybe with a 50 shot of juice!
I'm not telling you anything you don't already know.....but for others...........
Good 'ol 'Nick' says he is running the dyno @ 300 rpm/sec acceleration rate. That makes the engine work harder.
I've been in dyno contests where some participants wanted to run at 600 rpm/sec so they wouldn't stress their engines too much. It lets the engine wind up quicker.
You what? Go to a dyno contest and don't want to "stress" your engine?
I guess you could run to 7,000 rpm @ 7,000 rpm/sec (basically no load) and stress your engine even less. You wouldn't make any horsepower though.
Ran a pump gas 451 on the dyno at 300 rpm/sec and it made 770 HP. At 600 rpm/sec it made 740 HP. That engine loved to be worked hard. Was 300 rpm/sec a 30 HP cheat? Not if the engine can pull it!
And you can load an engine so hard it won't accelerate on the dyno, it just stalls.
nm9stheham
Well-Known Member
This info is very interesting... what in an engine would make it produce more HP when revving more slowly at WOT?
Could this possibly be a time response characteristic of the dyno? (I can see having filter capacitors on the senor lines that will slow the time response of the circuits...)
Think of a weight lifter lifting weights. He can press, say, 300# maximum. He can press 100# quickly. Just give it a shove and up it goes. Does that mean all he can lift is 100#? Stress him with the 300# and how quickly does the weight go up? The 300# forces him to exert more power. It was there all the time at 100#. He just wasn't using it.
Mechanically load an engine on the dyno. Hear it begin to grunt and exert more power. The dyno is pushing back on the weight lifter and pushing him to his upper stress level. His 300# maximum.
Mechanically load an engine on the dyno. Hear it begin to grunt and exert more power. The dyno is pushing back on the weight lifter and pushing him to his upper stress level. His 300# maximum.
nm9stheham
Well-Known Member
Mmmmmm.... not making sense to my wee brain yet.... that analogy would be like running the 600 RPM/sec test at something less than 100% throttle.
Just one other thought: some energy has to be going into the rotating mass ANY time the RPM increases. If you rev more quickly, that energy absorption rate into the engine's rotating mass is faster and that means more HP going into the rotating mass over that period of time, since HP is a timed rate of energy use. That makes a bit more sense.
Seems like a dyno would be able to compensate for that... BUT the operator has to program in a rotating mass (or moment of inertia) to make the compensation accurate.
I wonder if THAT is why to run at slower rates.... the end numbers look better!
Edit to add: Naw, it's not the rotational mass of the innards for the engine...I worked it out and it a just few HP at around 6000 RPM, not 30. That's without the flywheel/clutch or flexplate/TC... just right off of the crank.
Just one other thought: some energy has to be going into the rotating mass ANY time the RPM increases. If you rev more quickly, that energy absorption rate into the engine's rotating mass is faster and that means more HP going into the rotating mass over that period of time, since HP is a timed rate of energy use. That makes a bit more sense.
Seems like a dyno would be able to compensate for that... BUT the operator has to program in a rotating mass (or moment of inertia) to make the compensation accurate.
I wonder if THAT is why to run at slower rates.... the end numbers look better!
Edit to add: Naw, it's not the rotational mass of the innards for the engine...I worked it out and it a just few HP at around 6000 RPM, not 30. That's without the flywheel/clutch or flexplate/TC... just right off of the crank.
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I'm more layman than professional at this even though I own an engine dyno.
Took my A-Body 'Tetanus' to many dyno contests. Once went to a car show where they were running diesel trucks on a chassis dyno. I asked if I could run Tetanus on the dyno. The operator said, "Sure, bring it on up."
I don't remember exactly what 'ol Tetanus was making at that time but it was well over 600 RWHP. This was in, maybe 2008. On the first pull it made something like 580 RWHP. So I asked the operator, "Did you change the load on the rollers down from the diesel set-up?"
"Yeah. I took it down to a normal car setting. You won't be able to rpm at diesel load. The engine can't pull that. It will stall."
"Does 580 RWHP look like a normal car?"
"Ah, no. Do you want it back to the diesel setting?"
"Please."
Something like 640 HP was the result.
You can run at full throttle to your rpm, let's say 7,200, but not full load (torque) and the engine won't make it's potential horsepower at that rpm. It's like snapping the throttle open in neutral while sitting in your garage. Full throttle will get you to 7,200 rpm in a hurry if the engine doesn't puke itself all over the garage floor. It doesn't make much horsepower in neutral because it isn't producing much torque.
HP = TQ / 5252 X RPM. So......15 lb-ft / 5252 X 7,200 rpm = 20 HP.
Now make the same engine work, load it to say 562 lb-ft. Then we have 562 lb-ft / 5252 X 7,200 RPM = 770 HP. It will take longer to get to 7,200 rpm under load, than in the garage in neutral. Does that sound something like 300 rpm/sec vs 600 rpm/sec?
770 @ HP 7,200 rpm, is by the way, a real pull made by our pump gas 451. We actually have dozens of pulls in that range with the little 451.
300 rpm/sec holds the engine back (loads it) harder than 600 rpm/sec. If the engine has the ability to rpm at the greater load it will reveal more of the engine's horsepower.
Took my A-Body 'Tetanus' to many dyno contests. Once went to a car show where they were running diesel trucks on a chassis dyno. I asked if I could run Tetanus on the dyno. The operator said, "Sure, bring it on up."
I don't remember exactly what 'ol Tetanus was making at that time but it was well over 600 RWHP. This was in, maybe 2008. On the first pull it made something like 580 RWHP. So I asked the operator, "Did you change the load on the rollers down from the diesel set-up?"
"Yeah. I took it down to a normal car setting. You won't be able to rpm at diesel load. The engine can't pull that. It will stall."
"Does 580 RWHP look like a normal car?"
"Ah, no. Do you want it back to the diesel setting?"
"Please."
Something like 640 HP was the result.
You can run at full throttle to your rpm, let's say 7,200, but not full load (torque) and the engine won't make it's potential horsepower at that rpm. It's like snapping the throttle open in neutral while sitting in your garage. Full throttle will get you to 7,200 rpm in a hurry if the engine doesn't puke itself all over the garage floor. It doesn't make much horsepower in neutral because it isn't producing much torque.
HP = TQ / 5252 X RPM. So......15 lb-ft / 5252 X 7,200 rpm = 20 HP.
Now make the same engine work, load it to say 562 lb-ft. Then we have 562 lb-ft / 5252 X 7,200 RPM = 770 HP. It will take longer to get to 7,200 rpm under load, than in the garage in neutral. Does that sound something like 300 rpm/sec vs 600 rpm/sec?
770 @ HP 7,200 rpm, is by the way, a real pull made by our pump gas 451. We actually have dozens of pulls in that range with the little 451.
300 rpm/sec holds the engine back (loads it) harder than 600 rpm/sec. If the engine has the ability to rpm at the greater load it will reveal more of the engine's horsepower.
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nm9stheham
Well-Known Member
Well, it is a bit of head-scratcher for sure... .I am just not seeing how the engine's actual torque (and thus HP) at a given RPM would change just because the acceleration rate changed. Wouldn't that say that the cylinder fill, or the combustion burn, or the carb operation, changed due to the loading? (Or other drivetrain factors for a chassis dyno.) That's what does not make sense to me.
What I'd more readily suspect is in the dyno. It can't measure HP directly but has to compute that from the measured torque and the change in RPM versus time. And 'RPM pull' dyno's don't really measure torque directly.. they take the control voltage or current needed to regulate the acceleration rate, and, with hopefully good calibration, interpret that as meaning a certain torque (drag or load) was being applied to hold the engine back to a certain acceleration rate.
The accuracy of that translation from control voltage or current to actual load being applied is more likely IMHO where the torque, and eventually the computed HP numbers, will deviate from reality, and I can see that accuracy being better or worse going from one rate to another.
And there can/will be some errors introduced in the timing accuracy of the measurements made; small errors there get amplified more an more as the acceleration rates get higher an higher. The only way to fully get rid of that type of error would be to go to steady RPM running.
What I'd more readily suspect is in the dyno. It can't measure HP directly but has to compute that from the measured torque and the change in RPM versus time. And 'RPM pull' dyno's don't really measure torque directly.. they take the control voltage or current needed to regulate the acceleration rate, and, with hopefully good calibration, interpret that as meaning a certain torque (drag or load) was being applied to hold the engine back to a certain acceleration rate.
The accuracy of that translation from control voltage or current to actual load being applied is more likely IMHO where the torque, and eventually the computed HP numbers, will deviate from reality, and I can see that accuracy being better or worse going from one rate to another.
And there can/will be some errors introduced in the timing accuracy of the measurements made; small errors there get amplified more an more as the acceleration rates get higher an higher. The only way to fully get rid of that type of error would be to go to steady RPM running.
MopaR&D
Nerd Member
I think of it like a cycling machine at the gym. You can increase the resistance which is just a brake on the wheel but it still feels different than actually pedaling a real bicycle up a hill. With a dyno you aren't able to put a realistic load on the engine where it has to accelerate a mass, you load it down to where it stalls with a water brake then release the load slightly so the RPMs can rise; once the load is reduced the torque input to the dyno also goes down.
IMO the most accurate way is to load the engine at preset RPMs and "connect the dots" like was done back in the days before computer- controlled dynos. They would have a giant analog dial of torque output and for example the engine would be loaded at 2000 RPM WOT, torque would be written down. Then again at 3000, then 4000 etc etc. From that the HP would be calculated by hand. IIRC Chrysler also used gigantic weighted flywheels to determine HP, we're talking a flywheel with the same rotational inertia as trying to move a loaded Imperial down the road. No brakes to absorb torque and skew the numbers, just a huge mass to spin up.
IMO the most accurate way is to load the engine at preset RPMs and "connect the dots" like was done back in the days before computer- controlled dynos. They would have a giant analog dial of torque output and for example the engine would be loaded at 2000 RPM WOT, torque would be written down. Then again at 3000, then 4000 etc etc. From that the HP would be calculated by hand. IIRC Chrysler also used gigantic weighted flywheels to determine HP, we're talking a flywheel with the same rotational inertia as trying to move a loaded Imperial down the road. No brakes to absorb torque and skew the numbers, just a huge mass to spin up.
nm9stheham
Well-Known Member
Mmmmm, not quite the case: the torque from the engine does not change when the acceleration starts. Maybe you meant to say the drag from the dyno goes down?
- When it is at a steady RPM, the dyno load's drag (reverse torque, if you will) presented to the engine equals the engines torque; there is net zero torque, and so the system does not change speed.
- When the load's drag is reduced to start the 'run', the engine torque (input torque to the dyno) does not change at that moment, and now exceeds the drag, so you end up with net 'positive' torque in the system that accelerates everything.
MopaR&D
Nerd Member
I suppose so? lol... Just thinking out loud about how a water brake engine dyno works (at least the ones I've seen), the "torque" is measured simply by a strain gauge (force sensor) sensing how hard the turbine housing is being pressed against its stop by the rotation of the engine. The maximum force will occur when the engine is fully loaded at steady RPM but once that load is lightened to let the RPMs increase, the mutual force of the engine trying to push the dyno vs. the dyno trying to slow down the engine also goes down. So yes the torque output of the engine doesn't change but the way it's being measured does...?
This is why dynos are useless IMO for telling you how powerful your engine is, that's what drag strips are for. I'd much rather use vehicle weight and trap speed to find HP. Dynos help visualize how and where your engine makes power and what it likes as far as tuning goes but that's about it; there are multiple layers of calculations and measuring used in the dyno process that leave tons of room for errors or numbers-fudging.
To the OP: it happens time and again on here where someone will post numbers from a dyno run complaining they are too low (nobody's upset when they're too high, until they hit the race track lol) but they don't realize that it means nothing. If your car weighs 3400 lbs and hits 100 MPH at the end of a 1/4-mile that IS your power, doesn't matter if a dyno says the wheels are putting down 200 or 900 HP at the end of the day all that matters is how quickly that engine can accelerate a mass from a stop.
moper
Well-Known Member
I would hope it could. I'd be disappointed given the parts visible on this and the expected base rebuilding work with the numbers it made.
Some might be a stingy dyno, but it has full tube headers, no exhaust system, no fuel to pump, an electric water pump, and an aftermarket camshaft of some sort. Hard to tell given no info. But that's my gut anyway.
nm9stheham
Well-Known Member
OK, makes sense; that linear strain gauge, mounted so far from the axis of rotation, can be used to compute the drag (reverse torque) that the housing/dyno load is exerting on the engine. At steady state RPM, the dyno drag equals the steady state engine torque.
When the dyno is partially 'unloaded', it is set so that the lower housing torque relates to a certain lower dyno drag (reverse torque) against the engine. Then it measures how fast the engine accelerates over time. In the computations, it can compute that if the system accelerated so many RPM in so many milliseconds, then the engine's torque had to exceed the dyno drag by so many ft-lbs. So it can add that excess torque to the (hopefully well) known drag of the dyno, and say that the engine's torque is that sum.
The strain gauge accuracy versus actual drag for various drag settings, time measurement accuracy, rpm measurement accuracy, rotational mass that absorbs differing energy levels versus RPM and which has to has to be calibrated out, and computation errors can all contribute to this being off.
nm9stheham
Well-Known Member
So somewhat like the way the factories tested HP in the 60's HP wars....no fans, no alternators, etc.... i.e., not what it will really be in the car.
Interesting stuff. I kind of understand how it works. I would have to see and watch one up close to figure it out. If i can read between the lines here there are a lot of variables to cause inaccuracy. No big deal because it is just a estimate anyhow. Every dyno will give you a different number. Every operator makes it different as well. Hell, even a drag strip session will only tell you how much torque/horsepower it took to propel the car as fast as it went. Poor traction, fuel, conditions, etc all play a factor and the power you compute is only what it took for that run and not the maximum that the engine is capable of. Another point, the next time someone complains about Desktop Dyno results, they need to read through this thread. Those results can be as accurate as a trip down the strip or a engine dyno. All 3 are just estimates.
Exactly how we had to do it when testing Pop's NASCAR engines on 10,000 RPM's dyno in the 1970's.
We can do the same thing now. Next time I put one of our own engines on the dyno would be a good time to try that and compare it to the computer rpm/sec readout.
MopaR&D
Nerd Member
Cool we have the same train of thought lol. It all comes down to a bunch of "correction" factors to make that vague force reading from the strain gauge actually mean something.
@IQ52 that would be awesome to see a comparison of the different dyno methods, I myself am too young to have ever seen an old-school "analog" dyno but I've read about them in articles and interviews with old Chrysler engineers. There's also this video that shows a guy using an old-style dyno taking torque readings at individual RPMs that I found super interesting:
nm9stheham
Well-Known Member
Plus that computation of excess torque over the drag of the dyno....but it really can be made accurate if one goes to enough trouble and understands the equipment.
Probably where things go off the rails is that folks don't want to pay for some calibration service to come and set up to really put a know torque on the dyno. It would not be cheap or simple to do it brute force way..... a new 500 HP electric motor costs in the range of a few tens of thousands of dollars, and weighs 1-2 tons. And would take one heckuva power connection!
Sure. Intake, carb, cam, headers, good valve job why wouldn't it make that kind of power? He is also using an electric water pump on the dyno so that adds a couple ponies there as well
dartfreak75
Restore it, Dont part it!
Haha. Video thanks for sharing. I'd love to have access to something like that for tuning as far as timing and jetting goes.
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