505 dyno test results


496 polara

moparts id gch
FABO Gold Member
Feb 23, 2014
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North Carolina
My friend and hot rod mechanic for the last30 years freshened up his backup motor and decided to put it on the dyno.
4.35 bore x 4.25 stroke
185 psi cyl pressure
ported edelbrock rpm heads
trick flow intake
holley 850dp
Trick Flow track heat hyd roller
Intake Duration at 050 inch Lift:
Exhaust Duration at 050 inch Lift:
Duration at 050 inch Lift:
243 int./247 exh.
Advertised Intake Duration:
Advertised Exhaust Duration:
Advertised Duration:
296 int./300 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:
0.600 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:
0.600 in.
Valve Lift with Factory Rocker Arm Ratio:
0.600 int./0.600 exh.
Lobe Separation (degrees):
Dyno headers were 2 1/8 ( in car are smaller due to chassis )
617 lb ft at 4100
605 hp at 5600

The engine is Ford blue because it is in a Ford Fairmont of all things.

The heavy motor is still under reconstruction with trick flow heads and likely a call to Dwayne for a bigger cam. The car gets a steady diet of a 200 shot of giggle juice at the track as well.
I can't read it very well. But from what I can see looks to rip, is it possible you can take a closer picture of the Dyno sheet please.
Did the dyno operator let off before the end of the pull?
The reason I ask is the numbers look like they really drop off after the peak.

Std port BB strokers can be a challenge to make power in the upper rpm’s.

Any idea on the static CR?
He said 10.8-1 and after 5600 power fell off a cliff. I don't think they pulled it any higher. I wasn't there so I won't speculate. I would have thought a pull to 6000 just to see wouldn't have been out of the question.
I would have thought a pull to 6000 just to see wouldn't have been out of the question.

I agree. I at least would have attempted it.
If it didn’t want to go any higher than 5600, it’s as likely a lifter unhappiness issue as anything else.

Understand that power numbers vary from dyno to dyno, but that being said……..over 600hp from that combo wouldn’t be a bad number on the dyno here.

If the engine will need to rev past 5600 in the race car, which seems likely, you may have some sorting out left to do.
600/600 is a good number for RPM heads. They must have been ported correctly. 600/600 is usually what I expect for Trick Flow 240 heads on a 505.
He said 10.8-1 and after 5600 power fell off a cliff. I don't think they pulled it any higher. I wasn't there so I won't speculate. I would have thought a pull to 6000 just to see wouldn't have been out of the question.
HYDRAULIC roller . Solid flat tappet or solid roller? might give another 50, above 5500.
(Agree with PRH, lifter unhappiness, or not enough valvespring)
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IF…….. it’s indeed a lifter issue…….a set of solid rollers lashed tight “should” show improvements up top.

The curve looks pretty normal to me thru 5600.

A little dyno story……..

There was a dirt circle track motor on the dyno one day.
Built by a guy that worked for a shop we did dyno work for.
I wasn’t the one running this particular engine……and when I got to the shop they had already been making pulls.
They were doing some trouble shooting, thinking there was some sort of upper rpm ignition issue.
They couldn’t find one, so they went to make another pull, but the dyno wouldn’t load the engine…..at all.

So, they fill me in on what was going on and I try to make a pull……no go.

I see the upper limit was set at like 7200.
I look at the display of the last pull.
Last line is like 64-6500.
I was like, “oh………the last pull isn’t over yet. The computer is waiting for the engine to get to 7200 to end the program”.
Hit the “stop program” button…….motor loads up fine.
Make another pull……..motor just flat lines at 6500.
Hard into valve float(this was the “ignition problem”).

Builder couldn’t believe it…….since he got the recommended springs from the cam supplier.
He told me the pressures……nowhere near enough imo.
Done for the day.
Brought it back a few weeks later with different springs…….which were barely enough to get past 7k.
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It is a 80/20 car with the 80 being track. 31" tire with 4.10 gears. The old motor didn't rpm as high as this one. Smaller hyd roller and rpm intake. Still did a best of 6.05 @112 on the spray in the eighth. It should be an improvement.

I looked at his dyno numbers as a test of what my next build could do.
I have a 4.25 crank and cnc ported rpm heads. If I can swing the I would like to try a small solid roller on mine with an M1 intake (already have) and a 1000hp 4150 carb. Be just as happy with a solid flat tappet if I have to. Mine is a street car.
5200 and change at 112 in the eighth. Probably a good idea not to run it at a 1/4 track, if it doesn't rev as high as this one.
The moroso chart shows 112mph/31” tire/4.10 gears to be 5000 driveshaft rpm.
If you’re not driving thru the converter too bad, 5600 engine rpm might be enough to get it done.

For the OP’s future build, taking the Hyd lifters out of the equation should cure the power curve “falling off a cliff” as being a potential problem.
Just because the power peaks at 5600 doesn’t mean that has to be the end of the usable power curve.
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Hyd roller lifters can be a real problem to get dialed in correctly. I've seen engines spin to the moon with them but that rarely happens. What usually happens is they hit the wall around 6000 rpm. I have beehive springs in my 496 and it pulls pretty good.
If the throttle wasn’t released before the end of the pull, then I’d say something got unhappy.
(Loses 69ft/lbs in 177rpm)

Perhaps looking at some of the sheets from other pulls might show a trend.

Dyno story #2-
I had ported and set up some heads and got a cam for a customer.
They had the motor on a dyno local to them, and the power was really falling off pretty quick at the end.
And the repeatability of the upper rpm numbers was pretty poor.
He called me, we talked about it a bit.
I was pretty confident the springs were enough to go higher than what they were turning the motor, but conceded more spring was probably a good place to start.
So they got replaced with something that were about 100lbs more open pressure.
No difference.

The dyno I use here is a SF-901.
With their operating system, the computer will end the pull for you at the predetermined upper rpm limit.
You don’t need to anticipate it…….. keep the handle at WOT until you hear the motor get more load at the end, then let off.
The shop where this engine was being tested had the same kind of dyno…….. but……the operator was anticipating the end of the pull and was rolling out of the throttle early.

Just an “fyi”…….. the fuel flow, and with that……. The bsfc numbers on that sheet aren’t correct.
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