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5,200 rpm stop making power on dyno

  • Thread starter Thread starter vipsymbol
  • Start date Start date Apr 11, 2022
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vipsymbol

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#1
  • Apr 11, 2022
  • #1
I have HCI with stock block motor lays over at 5,200 make no more power

Big Heads and big cam

What could cause motor stop making power after 5,200 rpms
 

mob

the guy who hits on his mom
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#2
  • Apr 11, 2022
  • #2
Well with the literal zero info provided i'd say that sounds pretty normal for a 5.0
 
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Monkeybutt2000

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#3
  • Apr 11, 2022
  • #3
Valve springs, but need more info.
 
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General karthief

wonder how much it would cost to ship you a pair
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#4
  • Apr 11, 2022
  • #4
What heads, cam and intake?
Maf, throttle body, you know, other stuff.
 
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vipsymbol

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  • Apr 12, 2022
  • #5
11r 190 CNC tfs, 75mm, 42lbs, elbrok RPM, 1.6 rocker comps
comp cam 274hr, new MSD TFI

only bring this as I heard should be changed i have the orignal car(1989) Ignition Coil ...

MonkeyButt2000 - tell more about valve springs ....sounds interesting
 

KZGUNS

I can swing up to 11”
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#6
  • Apr 12, 2022
  • #6
vipsymbol said:
11r 190 CNC tfs, 75mm, 42lbs, elbrok RPM, 1.6 rocker comps
comp cam 274hr, new MSD TFI

only bring this as I heard should be changed i have the orignal car(1989) Ignition Coil ...

MonkeyButt2000 - tell more about valve springs ....sounds interesting
Click to expand...
Springs that are too light for the cam and rpm will cause valve float. What springs are you running?
 
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vipsymbol

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  • Apr 12, 2022
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KZGUNS said:
Springs that are too light for the cam and rpm will cause valve float. What springs are you running?
Click to expand...
Using the springs that came on the heads from Trick Flow
 

2000xp8

SN Certified Technician
Aug 8, 2003
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#8
  • Apr 12, 2022
  • #8
The sound floating valve springs makes is terrible.
It would be obvious not to go past their limit.
 

96pushrod

I think they're a little easier to get off
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#9
  • Apr 12, 2022
  • #9
What does the dyno graph look like?
You have an aftermarket fuel pump? What are you tuning the car with?
 

Dan02gt

mazing how much gas smell came from that tiny hole
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#10
  • Apr 13, 2022
  • #10
What's your A/F ratio doing when the power starts dropping off?
In my experience valve float is very noticeable as the engine acts like it has a bad miss.
 

mikestang63

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#11
  • Apr 13, 2022
  • #11
could be a few things

not enough fuel-nope- you have way too much injector btw
spark blow out
valves not adjusted properly
Cam installed or timing too advanced
exhaust too restrictive

that motor should be pulling up to with that combo. who assembled the motor
 

96pushrod

I think they're a little easier to get off
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#12
  • Apr 13, 2022
  • #12
mikestang63 said:
could be a few things

not enough fuel-nope- you have way too much injector btw
spark blow out
valves not adjusted properly
Cam installed or timing too advanced
exhaust too restrictive

that motor should be pulling up to with that combo. who assembled the motor
Click to expand...
Way too much injector??
 

mikestang63

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#13
  • Apr 13, 2022
  • #13
96pushrod said:
Way too much injector??
Click to expand...

42 lb injectors are way overkill for that setup. Injectors do not make HP they support it... 30#s are more than enough. This is a N/A build right? what is your A/F look like.
 

96pushrod

I think they're a little easier to get off
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#14
  • Apr 13, 2022
  • #14
mikestang63 said:
42 lb injectors are way overkill for that setup. Injectors do not make HP they support it... 30#s are more than enough. This is a N/A build right? what is your A/F look like.
Click to expand...
Injectors sorta make power, since without them nothing happens. Them being bigger than needed has no effect on anything, being smaller does.


Still waiting on a picture of the graph from op.
 

mikestang63

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#15
  • Apr 13, 2022
  • #15
96pushrod said:
Injectors sorta make power, since without them nothing happens. Them being bigger than needed has no effect on anything, being smaller does.


Still waiting on a picture of the graph from op.
Click to expand...


injectors do not make power- you can adjust the FP on 24's to work with this combo. It has to do with duty cycle, pulse width. You match the injector to support the HP needed- usually around 80% max duty cycle for N/A. 42's are overkill for this- he is no where near the HP where 42's are needed on a N/A motor . Too large an injector will make the pulse width very short causing driveability and tuning issues. the engine is only going to flow so much regardless of how big an injector you put on it. Hell you can play with the fuel pressure and probably use 24's at his power level. He's probably 350ish crank HP.

Is the OP running a stock EEC or does he have a tune to adjust the fuel curve. Even using a calibrated MAF only fools the EEC with changing the voltage, it may not compensate enough of pulse width at idle

Using your logic, throwing on 80# injectors would increase his hp? Curious to see what he has his FP set at and what his A/F is.
 

96pushrod

I think they're a little easier to get off
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#16
  • Apr 14, 2022
  • #16
mikestang63 said:
injectors do not make power- you can adjust the FP on 24's to work with this combo. It has to do with duty cycle, pulse width. You match the injector to support the HP needed- usually around 80% max duty cycle for N/A. 42's are overkill for this- he is no where near the HP where 42's are needed on a N/A motor . Too large an injector will make the pulse width very short causing driveability and tuning issues. the engine is only going to flow so much regardless of how big an injector you put on it. Hell you can play with the fuel pressure and probably use 24's at his power level. He's probably 350ish crank HP.

Is the OP running a stock EEC or does he have a tune to adjust the fuel curve. Even using a calibrated MAF only fools the EEC with changing the voltage, it may not compensate enough of pulse width at idle

Using your logic, throwing on 80# injectors would increase his hp? Curious to see what he has his FP set at and what his A/F is.
Click to expand...
Mike, you could stick 210lb injectors on his engine and it would idle just fine - I wouldn’t have him do it, but it would be doable. Thinking you need to match injectors to try and target 80% duty cycle makes no sense whatsoever. You can choose to believe that, but I know from practice that is completely untrue. Most all injectors available today can reliably supply fuel at very low pulse width. I would hope since the op had his car on the Dyno, it was being tuned in some sort of way.

Nothing about what I said suggests putting a bigger injector on his current engine would net him more power. You said injectors don’t make power, I was just saying without them nothing would happen. I Was kind of just being a smartass.
 
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General karthief

wonder how much it would cost to ship you a pair
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#17
  • Apr 14, 2022
  • #17
Like say'n 'it has a cam in it'
Why yes,,,,yes it does!!!
 

Noobz347

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#18
  • Apr 14, 2022
  • #18
I'm planning to run some oxygen along with my next build. I may mix in some nitrogen just to keep it all reeled in.
 

CAMTWO1070

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#19
  • Apr 16, 2022
  • #19
96pushrod said:
Mike, you could stick 210lb injectors on his engine and it would idle just fine - I wouldn’t have him do it, but it would be doable. Thinking you need to match injectors to try and target 80% duty cycle makes no sense whatsoever. You can choose to believe that, but I know from practice that is completely untrue. Most all injectors available today can reliably supply fuel at very low pulse width. I would hope since the op had his car on the Dyno, it was being tuned in some sort of way.

Nothing about what I said suggests putting a bigger injector on his current engine would net him more power. You said injectors don’t make power, I was just saying without them nothing would happen. I Was kind of just being a smartass.
Click to expand...
Putting 210lb injectors on a 302 and saying it will still run is highly false...

Before I get into that dont forget that an EEC is setup for the injector size its supposed to use and if you stick in a different injector the EEC doesnt recognize any injector you put in wont flow right and if the OP doesnt know he can pull a sparkplug and see the burn or add a lambda gauge and see his efficiency..

When I rebuilt my old f250 16yrs ago I tried putting bluetop 24lb/hr injectors to compensate for the 1.7 rockers I put in...The engine ran but the EEC didnt recognize the injectors as being yellowtop 19's so it ran limited,....

I sent the 19's out to be upgraded to 24's and put them in and the engine ran again but not as good as it should of so I sent the EEC to Kenne Bell and had it reprogrammed at the same time Mustang Magic was putting a KB supercharger in my 2001 Bullitt w/4.6 as they were the ones that suggested it and it worked out killer even with a speed density computer..

Now for the 210lb statement...Holley sent me 120lb injectors in a 36lb box and I didnt realize when I installed them.Theres no way low impedience injectors can be controlled in a high impedience environment without overheating the injectors and even with my chip I had giant issues getting it tuned until I realized the issue and I had them injectors in with a Terminator X setup that I thought was junk then ripped it out and put a Ron Francis harness and after debugging the harness still had major tuning issues with fouled sparkplugs and very gas loaded oil until I noticed the injector size was way off the mark..

Holley made good on sending me the right injectors but didnt respond to my gaswashed cylinders I had to rehone,pistons I had to rering or bearings I had to replace either and comes to show they dont stand behind their BS...........

Let me tell you my engine didnt run very well and sparkplugs lasted 10-15 mins idling and not even driving............



These plugs have literally 10 minutes of runtime on them........They look like they ran alot longer...............LOL

The exhaust was so rich even outside with a slight breeze it made my nostrils sting badly and it gaswashed the hell out of my cylinders too.........




Good Luck getting ahead with this issue OP
 

General karthief

wonder how much it would cost to ship you a pair
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#20
  • Apr 16, 2022
  • #20
A good dyno operator should have been able to tell what the reason for the lack of RPMs, I think he wasted his money on the run if the operator didn't discuss issues but without the graph showing more info we are stabbing in the dark.
 
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