missing when free rev

M

mtboggs

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Jul 13, 2014
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I have a 98 12 valve auto project truck that I'm turning into a pulling truck, it has full cut DVs, 5x018 modified DAP injectors, no fuel plate, 4K gov springs, 19.5 degrees timing, and Industrial injection s466 workstock/2.5 charger on it. on a free rev around 2,300rpms it misses, if I can get it to get past there it clears up and runs fine, and if it has any load on the engine it does not do it. Is it just because it's over fueled?
 
Don't free rev it. Problem solved. That pump isn't meant to fuel under no load.
 
DDually said:
Don't free rev it. Problem solved. That pump isn't meant to fuel under no load.
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I've never had one pop and sputter under free rev at any rpm... But as long as it runs fine under load I wouldn't worry either.
 
I've had 12v's that do it and some that don't. My 98 didn't pop at all but my 96 engine does.
 
I've had that before with lower timing and a mixture of stock gov springs
 
my 98 (913) pump did that when i would free rev it when the timing was 20 degrees, getting the timing bumped to 30 degrees fixed it, it will no load rev like a champ now. if your using it as a pulling truck you will definately want more than 19 degrees anyway.
 
my truck pop and sputtered under free rev with my old 370s and stock timing, once i bumped up the timing it ran like a camp
 
mine would pop at 2800. I cleared it up by adding fuel, maybe you have to lean yours out
 
sorry for taking so long to reply back been supper busy. The only reason I want to fix it is because i'm wanting to put a manual in for pulling, I'm worried that once I convert it then i'll have problems getting my rpms up on the line. And I've tried to lean it out, I've backed the star wheel off quite a bit and it didn't seem to change anything. Also I noticed when i'm spooling the turbo if I hold it at around half throttle or more it will bog done, I'm guessing that it's getting too much fuel?
 
Try revving it up slow. Otherwise, it's something that mine does when I have a little air in the fuel.
 
I have a similar problem but it is when I am coasting down hill in third and start to add fuel, it pops and sputters blue smoke like there is no tomorrow. I am pretty sure its a combination of low timing, air in fuel and low fuel pressure. Am I on the right track with my diagnosis?
 
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