5,200 rpm stop making power on dyno
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Well with the literal zero info provided i'd say that sounds pretty normal for a 5.0
Springs that are too light for the cam and rpm will cause valve float. What springs are you running?
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.
In my experience valve float is very noticeable as the engine acts like it has a bad miss.
mikestang63
SN Certified Technician
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
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
mikestang63
SN Certified Technician
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.
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
SN Certified Technician
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.
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.
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
Active Member
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
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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