What is happening on this dyno? Help

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68 barracuda 68

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finally get my engine back and went to a dyna pack and strange result..? Engine is 408 w2 ported heads , comp cam , 10,5 i comp, used dynamic converter 9,5 street and strip, stall 3800-4200
Tti headers and 2,5 all the way, 950 holley hp series, good pressure and mix, sooo what is happening at my engine on 5600? Is the converter the trouble? Thanks for help
 
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68 barracuda 68 said:
finally get my engine back and went to a dyna pack and strange result..? Engine is 408 w2 ported heads , comp cam , 10,5 i comp, used dynamic converter 9,5 street and strip, stall 3800-4200
Tti headers and 2,5 all the way, 950 holley hp series, good pressure and mix, sooo what is happening at my engine on 5600? Is the converter the trouble? Thanks for help
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I really can not read the graph, a thought is tire slippage?
 
68 barracuda 68 said:
View attachment 1715314060 View attachment 1715314060
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looking at those graphs, the horsepower curves are relatively smooth/flat once it gets up there, so I doubt its any slippage or converter issues. In my experience, itll spike,drop,spike in some fashion if something is slipping and then grabbing back. The torque curve does fall flat at higher RPMs, which is not unusual, the somewhat backtracking look to it does look off. Not sure exactly what would cause that yet looks like nothing drastic happens to the HP curve in either graph at the same time, but it does have a very slight blip there it looks like (pics are a bit small to tell for sure). So maybe a stumble in timing or fuel or something along those lines?
 
dukeboy_318 said:
looking at those graphs, the horsepower curves are relatively smooth/flat once it gets up there, so I doubt its any slippage or converter issues. In my experience, itll spike,drop,spike in some fashion if something is slipping and then grabbing back. The torque curve does fall flat at higher RPMs, which is not unusual, the somewhat backtracking look to it does look off. Not sure exactly what would cause that yet looks like nothing drastic happens to the HP curve in either graph at the same time, but it does have a very slight blip there it looks like (pics are a bit small to tell for sure). So maybe a stumble in timing or fuel or something along those lines?
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The fuel pressure are good all the way, everything is in good shape , i also think it was problem with fuel but not any drops there, level in carburator also good, no powerwalve back and 92 and 82 in front of carburator holley 950. Tried also timing on 38 same result as on 36, its easy to take it to 7000rpm but the horsepower cuts off at 5500rpm... the roller comp cam should work from 3400-7400 but i dont understand whats happening her, the test was on a dyna pack
 
68 barracuda 68 said:
The fuel pressure are good all the way, everything is in good shape , i also think it was problem with fuel but not any drops there, level in carburator also good, no powerwalve back and 92 and 82 in front of carburator holley 950. Tried also timing on 38 same result as on 36, its easy to take it to 7000rpm but the horsepower cuts off at 5500rpm... the roller comp cam should work from 3400-7400 but i dont understand whats happening her, the test was on a dyna pack
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Whats your cam and valve train specs
 
Frankly, I’ve seen several dyno sheets from(I believe) a dynapack(hub/axle dyno, right?)from old school auto trans combos that didn’t make any sense at all to me.

I have zero faith in chassis dyno results being able to be directly correlated to arrive at crank tq/hp figures, or be able to get any real sense of what the engine power curve looks like.

About the only thing I feel you can learn with this type situation is making sure that the fuel and ignition systems in the car are functioning correctly, and that the carb a/f ratio is at least in the ball part.

What I def wouldn’t be doing is chasing something around in the engine combination based on the numbers I was seeing from a hub dyno, with my old muscle car and an auto trans.

The chassis dyno owners will flame me for this...... but....... I don’t feel it’s wise to try and sort through an “engine” combination by running the car on the chassis dyno.
Sort the motor out on the engine dyno first, then if some final tuning with the motor in the car is desired...... put the car on the chassis dyno.
 
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68 barracuda 68 said:
The fuel pressure are good all the way, everything is in good shape , i also think it was problem with fuel but not any drops there, level in carburator also good, no powerwalve back and 92 and 82 in front of carburator holley 950. Tried also timing on 38 same result as on 36, its easy to take it to 7000rpm but the horsepower cuts off at 5500rpm... the roller comp cam should work from 3400-7400 but i dont understand whats happening her, the test was on a dyna pack
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dukeboy_318 said:
Whats your cam and valve train specs
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Cam specs is duration @050 lift 263, valve lift 0,649 inntake. Valvetrain is w2 and some work to get this on place but should be all fine, checked today also the valvetrain an lokks perfekt
 
If the power curve is to be believed, about the only thing I can think of that would have the motor nosing over like that would be not enough spring load, or pushrods not up to the task.

Do you know what the springs/pressures are?
Pushrods?
 
PRH said:
If the power curve is to be believed, about the only thing I can think of that would have the motor nosing over like that would be not enough spring load, or pushrods not up to the task.

Do you know what the springs/pressures are?
Pushrods?
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I dont know wich pressure they are, what i know is that engine builder is that they are new and shims to get them perfeckt, i was also worried about valvetrain but looks good 240 pounds says the builder
 
I can’t really make out the images you posted.
What are the green and light blue lines?
Green is tq?
Blue is HP?
 
That tq curve isn’t that unusual for a car with a loose converter being tested on a chassis dyno.
When the converter is slipping a lot there is tq multiplication.
So, if the motor makes peak tq at a fairly high rpm(which yours should with a [email protected] roller cam and w2 heads), in the lower rpm area of the powerband, up until around the point of peak tq, you have the natural upward trajectory of the tq curve, which is also being boosted somewhat by the converter slipping/multiplying the tq.
Then, when the converter starts to lock up and the motor reaches its natural tq peak, you lose the boost of the tq multiplication, along with the motor peaking.......after that point, then the power(to the wheels) falls off at a quicker rate than it would if there hadn’t been a converter in the mix in the beginning.

What I’m seeing, for a graph taken off a chassis dyno, tested with a motor with a loose converter behind it...... that curve doesn’t look abnormal to me.
 
Why didn't torque and HP cross at 5252 rpm?? Given starting point, they should have crossed
 
who ported the heads ? Do you have a flow sheet ?
What are all the specs on the cam ? What springs ?
What intake ?

3" Exhaust wouldnt hurt....
 
I can’t see it too well, but it looks like the tq and hp are on different scales, and the tq is not in ft/lbs....... its in nM.
 
PRH said:
I can’t see it too well, but it looks like the tq and hp are on different scales, and the tq is not in ft/lbs....... its in nM.
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Yes its in nm, i think i found the fault : one rocker is very loose and also think in cold engine the clerance should not be 40 on cold engine be 50, hopeffully i can take it to then dyna pack fast and see again..
 
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PRH said:
I can’t see it too well, but it looks like the tq and hp are on different scales, and the tq is not in ft/lbs....... its in nM.
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Yes..He is in Norway.

10,000 Swedes ran thru the weeds chased by 1 Norwegian......
 
I can’t make out the hp scale on the right side, but it looks like about 665nM tq@5252-ish, which is about 492ft/lbs(which would be 492hp at that same rpm).

.50mm lash is about .020”..... which is either tight or not, depending on the design of the cam lobe.

No lash specs on the cam card?
 
PRH said:
I can’t make out the hp scale on the right side, but it looks like about 665nM tq@5252-ish, which is about 492ft/lbs(which would be 492hp at that same rpm).

.50mm lash is about .020”..... which is either tight or not, depending on the design of the cam lobe.

No lash specs on the cam card?
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Yes the cam specs says 0,22 and 0,2 on in, before there 0,4mm on all on cold engine, so hopefully find the problem now, and also one was very loose rocker arm
 
68 barracuda 68 said:
Yes the cam specs says 0,22 and 0,2 on in, before there 0,4mm on all on cold engine, so hopefully find the problem now, and also one was very loose rocker arm
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Another almost simular car and engine was at the same dynapack, and simular test. Its the loose converter and the dynapack do not work together.. so going to a track with dual afr and tune it.
 
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