Dyno session results are in!

[AdamIsAdam]

Hey all. I finally got my car on a dyno this weekend and I could NOT be happier! I bought the car, so I'm not bragging about my own work. With that being said, CHECK OUT THIS CURVE! The torque is as flat as Kansas and the horsepower looks like the price chart for toilet paper in the early months of COVID-19!

It's a 347 stroker. Short block by Ford Strokers (est 10.5:1). TEA Twisted Wedge 185 64cc heads. Custom made cam. Custom Pro Systems 780 Holley. MSD Digital, MSD distributor.

The car always starts right up, even in the winter without a choke. Never runs hot. Just drives great. And to know that it's got 385hp at the wheel (so maybe 450+ at the crank) with great, flat torque, that just confirmed what my butt dyno said: Snake goes good.

I'd love to hear feedback from others who have built similar engines or who just have something to say on the subject.

According to the racing calculators, with this power:weight and 3.55's with 25" tires the car is capable of low 10's! (assuming it could ever hook up of course!) Very cool.

With numbers like this, who needs a big block? hehehe

I was just watching Jay Leno interviewing John Morton who said Shelby only raced the 427 once. All the wins were in 289's. Mostly because by the time the 427 came out they were heavily into the GT40's.

https://youtu.be/6hhnwAYj-Jc

https://youtu.be/QboLm0fO7Yo


By the way, it made the most power with the air cleaner on and hood closed! Go figure.

[Alfa02]

Wow, great NUMBER'S Adam. When Bruce Snyder talked to the first owner. He had just built a 347 for himself (Also knows FFR quite well) when we were looking at this car for you, he said it had a Dart block, the best starting point for a 347. Cheers TommyRot

[AdamIsAdam]

Sadly, it's not a Dart block. I think Ford Strokers use 80s-90s 5.0 blocks as starting points, unless you upgrade to the Darts as you said. I'm told the 5.0's are safe to 500-600 or so, right?

[blykins]

I’ve seen factory blocks split in two at about 450-500 hp. Lot of variables there but I would never tell anyone they can handle 600 hp.

I’m trying to figure out the dyno curve because that torque portion is pretty unrealistic. I was thinking it was the way they have it plotted but you would not see a straight line from any engine. The numbers are somewhat realistic but the shape of the curve is basically impossible.

[Anthony]

Originally Posted by AdamIsAdam

I was just watching Jay Leno interviewing John Morton who said Shelby only raced the 427 once. All the wins were in 289's. Mostly because by the time the 427 came out they were heavily into the GT40's.
.

Actually, the reason is that shelby did not have the 100 required 427 Cobra’s built to satisfy the requirement to qualify the 427 for the production class, so the 427 had to compete in the prototype class along with the gt40. So the 427s were not raced, and the 427 super coupe was never completed, and shelby concentrated on the gt40s. Later on, the 427s were successfully raced by privateers.

[AdamIsAdam]

Originally Posted by blykins

I’m trying to figure out the dyno curve because that torque portion is pretty unrealistic. I was thinking it was the way they have it plotted but you would not see a straight line from any engine. The numbers are somewhat realistic but the shape of the curve is basically impossible.

Why is this torque curve so unrealistic? I've attached pictures of the dyno screen showing all 3 pulls. I also googled flat torque curve dyno sheets and found a few others that are very flat looking. I am honestly asking, why is this impossible?

https://www.miataturbo.net/attachmen...r-sec-line.jpg

and

https://www.dragtimes.com/images_dyn...ccord-Dyno.jpg

[blykins]

A 347 does not have the torque curve of a diesel truck.

My guess is the smoothing that is turned on has all but removed any curve shape.

Even the 482 inch big blocks that I build for towing applications do not have that flat of a curve.

You would have had a better chance of a flat torque curve if the engine had not been high strung. The trend that we see is that when hp peaks are at higher rpms and hp reads higher than torque, the torque peak is high as well and the curve is peakier as well.

By your graph, it reads that at any rpm, your torque is essentially 340 lbft. It just doesn’t happen like that. It’s also not logical that your hp peak was at around 6200 and your torque peak was at 3000.

[AdamIsAdam]

Originally Posted by blykins

A 347 does not have the torque curve of a diesel truck.

LOL.

My guess is the smoothing that is turned on has all but removed any curve shape.

That makes sense. What does the smoothing setting of "5" mean? I assumed it meant 5 ft. lbs, but I think you're suggesting it's smoothing more than 5 ft. lbs.

You would have had a better chance of a flat torque curve if the engine had not been high strung. The trend that we see is that when hp peaks are at higher rpms and hp reads higher than torque, the torque peak is high as well and the curve is peakier as well.

By your graph, it reads that at any rpm, your torque is essentially 340 lbft. It just doesn’t happen like that. It’s also not logical that your hp peak was at around 6200 and your torque peak was at 3000.

Can we at least agree that it's a decent looking graph in general? Don't rain on my parade!


Seriously though, what I can say, is that based on how the car feels and drives, this chart did not shock me. Again, I'm no expert and am only going by my butt dyno (which has been in a lot of seats over the last 5 decades). But it does pull like a diesel at any RPM and it SCREAMS up top. It feels like it would pull forever if it not for the rev limiter.


EDIT: I found this on smoothing

https://www.corvetteforum.com/forums...hing-mean.html

Looks like as much as 8hp swing per this thread. But it won't change the charted line, just smooth out the peaks and valleys.

[blykins]

I would just look at the peak numbers.

I’ve been looking at dyno sheets for the last 17 years and that one isn’t logical by any means. It almost looks like a slipping torque converter or a slipping clutch if I didn’t know any better.

Do a search for 347 engine dyno sheets and you’ll see what a typical dyno sheet should resemble.

[blykins]

Here’s something a little more logical:

https://www.stangnet.com/mustang-for...inally.780323/

[Anthony]

Here's a roush 427R in a cobra, on a dynojet. Kind of a flat torque curve that tapers off at 4400 rpm's.

[blykins]

Yes, that’s more like it. Some variation at the beginning when the engine is loaded, the torque trait itself, then it peters off as hp goes up.

All in all, that engine should have more of a flatter curve than the OP’s 347, as it is cammed to have a flatter curve (verified by more peak torque than hp) and the displacement is much larger.

[DanEC]

Originally Posted by Anthony

Here's a roush 427R in a cobra, on a dynojet. Kind of a flat torque curve that tapers off at 4400 rpm's.

Wonder why the HP and torque curves do not cross at 5250 rpm on this one?

[blykins]

They would if the scales were the same on each side.

[eschaider]

Originally Posted by blykins

Here’s something a little more logical:

https://www.stangnet.com/mustang-for...inally.780323/

+1 on Brent's comments. The only way I know to get a relatively flat torque curves is a PD blower that forces air in the cylinders at lower rpms. Otherwise you have a curve that ramps up to a peak value between 3800 and say 5400 rpm depending on heads and cam and then starts to roll over with increasing engine speed.


Ed

[legenmetals]

Here is a dyno pull on my 358 c3 Ford in my TA car.


https://www.hotrod.com/articles/358-...ord-dyno-test/

[eschaider]

Originally Posted by legenmetals

Here is a dyno pull on my 358 c3 Ford in my TA car.


https://www.hotrod.com/articles/358-...ord-dyno-test/

Your data recording starts at 5000 rpm which is usually within 500 rpm (give or take) of a normal engine's peak torque. In the FWIW category, your C3 Heads, and for that matter your entire engine, fit into the fairly impressive category of a purpose built race engine. Because your engine, in actual fact, is a thoroughbred race engine it will likely peak its torque in the mid 6000 to 7000 rpm range because of heads and camming.

If your dyno pull was from a lower engine speed in the 2000 to 2500 rpm range (like the OP) the measured torque would be substantially lower until the engine speed and port air flow got up significantly, like they are at 5000 rpm and higher.

The only way to get the cylinder fill necessary for the table flat torque curves down low in the engine speed is with some type of positive displacement blower to produce the near 100% Ve necessary at the lower engine speeds for the flat torque curve.

Any naturally aspirated engine is going to show substantially reduced torque at 2000 engine rpm unless you are looking at something like a stationary power plant engine that has a peak engine speed in the 2000 -2500 rpm range. That's not what we use in these cars and that is not what you have.

What you do have is a 358 inch NASCAR or Cup engine that is purpose built to work in the 5000 to 8000 rpm range. In that rpm range, which it was designed to operate, you do have a very desirable and exceptionally flat torque curve for that generation engine.

Your engine compared to the typical Cobra replica engine is like comparing a greyhound to a border collie. They are both great dogs but they are very different dogs and so is their care and feeding.


Ed

[olddog]

This is off subject a bit, but the 4 valve per cylinder modular engines achieve exceptionally flat torque curve, especially on the low rpm just above idle. They did this by only using one intake port and valve until the rpms were up enough to keep the port velocity high with both valves.

I only point this out as, one of many, short comings of two valve per cylinder head designs.

You need air volume to make torque. You need velocity if you are trying to pack the air into the cylinder at or past BDC. It is difficult to get low rpm port velocity and not end up with the small port restricting the volume at high rpm. To make power at high rpm you have to give up low rpm torque.

Big truck engines make moderate torque with large ports and small duration cams. They do not have good port velocity, and they are out of breath by 3000 rpm usually. In the small range they operate in, they have a relatively flat torque curve. You have to go to a diesel to get a flatter low end torque.