427w back from rebuild with dyno results

[tortuga]

Going to have to with better clutch...looking forward to not using oil!

[patrickt]

Well those numbers look pretty good but I always wonder when I see that "corrected" stuff at that top....

[RUFdriver]

Nice numbers Dude!

[hauss]

Who did the build? and what size motor? Please more info and I agree with rufdriver nice numbers dude.

[eschaider]

Originally Posted by patrickt

Well those numbers look pretty good but I always wonder when I see that "corrected" stuff at that top....

It's just one of the two SAE corrections that Detroit has used over the years, Patrick. Pretty much standard stuff.


Ed

[tortuga]

Originally Posted by hauss

Who did the build? and what size motor? Please more info and I agree with rufdriver nice numbers dude.

351w stroker, 427+over bore, ford racing boss block, z304p heads, trick flow R intake, 850xp carb

Built up in windsor Ca...their own secret cam.

[patrickt]

Originally Posted by eschaider

It's just one of the two SAE corrections that Detroit has used over the years, Patrick. Pretty much standard stuff.


Ed

But what am I to make of all the youtube vids and posts showing how to fake dyno numbers? And all the threads, including this forum, where dyno operators tell us they can manipulate the numbers at will?

[Tommy]

Tortuga - Great looking engine. I bet it sounds good too.

Over the years I've noticed lots of guys with street cars putting their dyno HP number in their screen name or signature. And it appears that many of them spent many thousands of dollars for performance they can talk about but will never fully use. I did something similar recently when I ordered a custom engine equipped largely to look and sound right. I didn't specify a HP number to the builder and I picked components less likely to fail sooner (e.g., no solid lifters or high ratio rocker arms). The engine builder, who likes to post dyno videos online, made multiple dyno runs making adjustments to whatever, to achieve one run breaking the 600 HP mark. I feel confident it was more about his future business than me.

The bottom line for performance is that engine dyno numbers don't mean much. What matters is chassis dyno numbers with all the accessories, exhaust and other factors brought into play. For me, all that matters is that it looks good and sounds great.

[Mark IV]

Originally Posted by Tommy

The bottom line for performance is that engine dyno numbers don't mean much. What matters is chassis dyno numbers with all the accessories, exhaust and other factors brought into play.

They pay for big dyno numbers and then try to put the power down via BFG TA tires!

[eschaider]

Originally Posted by patrickt

But what am I to make of all the youtube vids and posts showing how to fake dyno numbers? And all the threads, including this forum, where dyno operators tell us they can manipulate the numbers at will?

Sadly, for the most part, that is true of virtually all adjustable mechanisms that require setting a baseline or datum reference. Even after the datum reference is established then you need to frequently apply a scaling factor to account for differences in air density, correcting back to an accepted standard for temperature and pressure. Ultimately you rely on the honesty and integrity of the operator / shop. Eventually the bad eggs usually, but not always get weeded out.

There is more than one performance related business that fits into the ought to be weeded out category. Usually, but not always, their customer service or quality of service / workmanship track record tags them for who they really are. The tough part is the new charlatans who have not yet done enough damage to get their own dot on the charlatan radar screen.

I undrerstand your caution and also healthy concern over reported dyno numbers. One of the quick and dirty ways to assess dyno veracity is to measure the pounds of air consumed at a given engine speed to validate the power. The magic number is 10 lbs of air per 100 HP. When the power numbers exceed this number they suspect.

Like a burner, of any type, there is a maximum amount of energy it is capable of delivering. Engines are no different. That magic metric is 100 HP per 10 lbs of air consumed. Very easy to get below that number. Not impossible, but virtually impossible to get above it.


Ed

[Tommy]

I believe that rule of thumb is 10 pounds of air per minute per 100 HP.

[MKS427]

What octane is recommended by the builder? What is the compression & cu in?

[tortuga]

Originally Posted by MKS427

What octane is recommended by the builder? What is the compression & cu in?

She calcs out at 10.8:1, 91 octane...The actual Cu in im not sure whatever the overbore is? With a 4" stroke a .02 overbore would add about 4.25 CI if my math is right so ~431 or so?

I was impressed with the numbers, i don't really NEED as much power as possible, just thought it was an interesting stable looking curve, just sharing. Its actually going to need a stouter clutch based on its torque capacity than the one i had...Fun to brag about at cars and coffee will i use it? Not really...

The impetus was to tear the motor down and put it back together right, its burned oil from day 1. I put the ported heads on just because i got a smoking deal on a brand new pair.

Seems Ford Racing uses alot of cool guy bits but falls short on the actual build from what i was told by the builder.

[olddog]

Patrick,

The reason to correct for horse power is that if you dyno an engine along the coast, sea level, and dyno that same engine in Bolder Colorado, the uncorrected results is extremely different. The entire question is how many cubic feet of air is how many pounds of air. A pound of air is a constant. How many cubic feet it take to make a pound of air is not constant.

[eschaider]

Originally Posted by Tommy

I believe that rule of thumb is 10 pounds of air per minute per 100 HP.

You are correct Tommy.

I failed to include the ever important time dimension. Without the time dimension the metric is of little value. Thanks for the dilligence and heads up.


Ed

[eschaider]

A couple more thoughts on correction factors for inquisitive minds:

The primary reason a correction factor is employed is to compare testing performed under different atmospheric conditions, high altitude (Denver?) vs low altitude (Coastal Cities) including ambient air temps less the impact of humidity. The correction factor will contain a temperature, barometric pressure and an efficiency percentage that is used to bring all test results to a level playing field.

There are two different correction factors that Detroit has used for 'normalizing' dyno results. One is the SAE J607 correction factor that corrects to 60˚F and 29.92 inches of mercury. The second SAE correction factor is J1349 which corrects to 77˚F and 29.31 inches of mercury.

In both cases wet bulb readings are used to calculate a saturated, current and corrected vapor pressure. The corrected vapor pressure is then subtracted from the observed barometric pressure because this pressure in the ambient air is attributable to water vapor and not air (remember the 10 lbs per minute per 100 HP metric) This methodology will yield corrected barometric pressure.

The corrected barometric pressure is used to calculate the correction factor for each standard. Once the correction factor has been determined the observed dyno power is multiplied by the correction factor to get the corrected power output.

Now for those inquiring minds the actual correction factors are calculated as follows:

J607 Correction Factor Calculation

........CF= [(29.92/Corr Baro)^(1.2)*{(Inlet Air Temp+460)/(520)}^0.6]


J1349 Correction Factor Calculation

........CF= 1.18*[(29.31/corr Baro)*{(Inlet Air Temp+460)/(537)} ^0.5]-0.18

The easiest thing to remember is cooler air and higher barometers produce more power and hotter air and lower barometers produce less power. This is why legit shops use correction factors to normalize measured power irrespective of atmospheric conditions at the time of the test.


Ed

[tortuga]

Mc cleod
Anyone care to xplain how the heck this works?

[Gaz64]

That is a dry twin disc clutch. Works with the same principle as multiplate wet clutches in Automatics or motorcycles. The "Steels" are the driving member, the "Frictions" are the driven member.
The more plates you have, the more torque capacity the clutch has. Automatics have 6 or more plates per stack, since they need to get the torque capacity in a small package.

[eschaider]

+1 on what Gary said ^.

Couple of additional thoughts;

McLeod makes two versions of that clutch. One is called RST and the other is RXT. Either one will have a showroom soft feel to the clutch pedal release effort required. The RST will provide a very nice daily driver experience.

If you race the car and also have north of 550 ft/lbs of torque the RXT might make a better choice form a life point of view. From a daily drive point of view the organic material discs will be buttery smooth on engagement and a real pleasure to drive around with. If you only occasionally race the XT is probably not the right clutch for you, the RST is.

Ed

[Tommy]

Originally Posted by Gaz64

That is a dry twin disc clutch. Works with the same principle as multiplate wet clutches in Automatics or motorcycles. The "Steels" are the driving member, the "Frictions" are the driven member.
The more plates you have, the more torque capacity the clutch has. Automatics have 6 or more plates per stack, since they need to get the torque capacity in a small package.

Let me be sure I've got this. The black ring attaches to the flywheel and the metal disc between the two friction discs so those three metal parts turn as one. When the clutch is engaged, the forward friction disc presses against the flywheel and the aft friction disc presses against the metal disc. Is that correct?