Struggling at high rpm above 6000

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Jax

Jax

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410 stroker, with Magnaflow fuel system, Pro systems 850CFM car, MSD Digital 6 plus ignition with billet distributor.....

The car is running clean up to 6000 rpm, after that the engine starts to struggle " kind of misfire".
We have changed fuel jets, spark plug gaps, changed plugs. But nothing seems to help.
Even when we close the gap from 0.045" to 0.030" it when worst. The car starts bugging completely down after 6000 rpm... I have the feeling it is somewhere in the ignition....

Any help will be appreciated
 
It doesn't need to go higher. Stroker's make torque down low. If you want a 7000 rpm screamer, build a 273!
 
Jax said:
410 stroker, with Magnaflow fuel system, Pro systems 850CFM car, MSD Digital 6 plus ignition with billet distributor.....

The car is running clean up to 6000 rpm, after that the engine starts to struggle " kind of misfire".
We have changed fuel jets, spark plug gaps, changed plugs. But nothing seems to help.
Even when we close the gap from 0.045" to 0.030" it when worst. The car starts bugging completely down after 6000 rpm... I have the feeling it is somewhere in the ignition....

Any help will be appreciated
Click to expand...

Here's a couple of wild guess's.........you are running out of gas, need more volume to the carb or valve springs are weak
 
Our 416 has seen 9000 with out skipping a beat. Sounds like you have a valve train issue. We run a billet with a digital 6 and a 1050. Check all your grounds get race plugs and a coil that is 6 and 7 approved.
MSD 8251 MSD Ignition Coil - Pro Power HVC - Red

Steve 102.JPG
 
Last edited:
WHat is your fuel pressure at WOT?

What is the AFR at 6,000?

What is your top end limiter set to?

What ignition are you running?

WHat is the LSA?

What is the timing at 6k rpm?
 
If it runs into the wall at the same rpm point in every gear, it’s likely a valvetrain control issue.

Are you running a hyd cam?
 
What is the limiter set at? They come in pretty early. What cam! Hydr/solid? Status of springs? Age? AFR gauge will cut down on the possible causes. If its lean, fuel supply. Rich, could be ignition. Varies considerably. Valve train. When I spin mine to 6700 it just stops pulling. Doesn’t act up, just no power. More info needed
 
Might be your ignition box. If you have a friend with a working box see if you can borrow it for a few hours to test it out. Also, I have heard stories of these boxes having issues with the rev limiter functions....try turning them off for a pass (just don't launch hard incase you snap a u-joint and zing engine).
 
mbaird said:
Boy this sounds familiar ....
What cam ?
Click to expand...
A little information from his other thread.

Hi,
My setup is:
Procomp heads with PAC SPRINGS ( Double springs with damper )
Solid cam .600 lift
Eagle forge crank, rods and pistons. ( Balanced )

At the moment I am crossing finish line @ 7200 rpm.

What is your feedback? Or what is the suggested max rpm for this set up


Maximum RPM under load




...
 
Oldmanmopar said:
Our 416 has seen 9000 with out skipping a beat. Sounds like you have a valve train issue. We run a billet with a digital 6 and a 1050. Check all your grounds get race plugs and a coil that is 6 and 7 approved.
MSD 8251 MSD Ignition Coil - Pro Power HVC - Red

View attachment 1715817234
Click to expand...
The challenge I am having that it may be a valve train issue, is that I am getting the same 127 mph that I ran before the issue started.... So in other words, I am not loosing that much power.
 
PRH said:
I agree with the turning the rev limiter “off” as something I would try.
Click to expand...

As a temporary test, I'd agree

More on cam, if you have a very tight LSA it is going to fall off much quicker. My fathers engine is that way, freight train to peak HP and then gets soggy, quick.
 
Ok guys, thanks for all the feedback. Let me share some more details of how everything started...

Engine: Procomp heads with PAC SPRINGS ( Double springs with damper )
Solid cam .600 lift
Eagle forged crank, rods and pistons. ( Balanced )
Fuel system: Magnaflow pump, Pro systems 850 CFM carb
Ignition: MSD 6 AL Digital with MSD Blaster HVC 2 Coil, and MSD wires.
Champion RC12YC plugs.
I am running C12 mixed with pump gas.

Everything was running fine.

1 month ago, we installed a nitrous kit and a higher carb spacer....... ( the nitrous hasn't been activated or used )...... Here is where the problems started.

This weekend we tried:

Change from Champions spark plugs to NGK-7. We thought it was just fouled plugs.
Increase Carb jetting:
Front: from 76 to 80
Rear: from 86 to 88.
This helped a little bit....and struggling when almost away, but still there...
We changed the gap from 0.045 to 0.030, and the car felt on his nose passed 6000 rpm, It was literally like the car switched off...then came back to life......
We changed the gap from 0.030 to 0.045 and the misfire was there again, but didn't felt on his nose...
 
roccodart440 said:
As a temporary test, I'd agree

More on cam, if you have a very tight LSA it is going to fall off much quicker. My fathers engine is that way, freight train to peak HP and then gets soggy, quick.
Click to expand...

This is my cam info:

upload_2021-11-8_16-7-19.png
 
1 month ago, we installed a nitrous kit and a higher carb spacer....... ( the nitrous hasn't been activated or used )...... Here is where the problems started.
Click to expand...

Seems like it would have been worth removing the taller spacer/nitrous kit and putting it back to how it was when it ran good.

In your other thread there is mention of crossing the line at 7200, 29” tires, 4.11 gears, and 127mph.
If all of that is correct, then the converter is slipping 20%....... and is junk.
 
Jax said:
Ok guys, thanks for all the feedback. Let me share some more details of how everything started...

Engine: Procomp heads with PAC SPRINGS ( Double springs with damper )
Solid cam .600 lift
Eagle forged crank, rods and pistons. ( Balanced )
Fuel system: Magnaflow pump, Pro systems 850 CFM carb
Ignition: MSD 6 AL Digital with MSD Blaster HVC 2 Coil, and MSD wires.
Champion RC12YC plugs.
I am running C12 mixed with pump gas.

Everything was running fine.

1 month ago, we installed a nitrous kit and a higher carb spacer....... ( the nitrous hasn't been activated or used )...... Here is where the problems started.

This weekend we tried:

Change from Champions spark plugs to NGK-7. We thought it was just fouled plugs.
Increase Carb jetting:
Front: from 76 to 80
Rear: from 86 to 88.
This helped a little bit....and struggling when almost away, but still there...
We changed the gap from 0.045 to 0.030, and the car felt on his nose passed 6000 rpm, It was literally like the car switched off...then came back to life......
We changed the gap from 0.030 to 0.045 and the misfire was there again, but didn't felt on his nose...
Click to expand...


What is your compression ratio? Seems weird to runs 12 heat range plug and then mix C12 in there. If your compression is so low you can run a 12 you don’t need the C12.
 
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