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Old 07-23-2012, 08:36 PM
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olds 455 flattening out at wot

Ok so i got the fuel dripping issue from my last post straightened out. I took the car out and its off idle response and power are great but at wide open throttle in higher rpms it flattens out and just doesnt want to go any faster. Breaks up a little bit too. I am running a holley 750 double pumper with points. Dwell is at 30 degrees. I started with timing at 12 degrees. one thing i noticed is when i adjust timing at idle with vacuum advance plugged the engine idles alot smoother when i add advance. Its off the timing pointer though when it runs its best. I did not drive it though because i was afraid to mess something up with so much advance. Would a stretched timing chain cause the bogging and timing marks being off? I realize the balancer could of moved on itself too so should i adjust timing at idle until the engine sounds its best and run the car to see if the bog is gone?

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Old 07-23-2012, 08:50 PM
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There can be several reasons for this and they are:
It's not getting fed enough volume of fuel to the carb at high RPM.
The spark is so weak it can no longer ignite the mixture, this is also followed with popping.
The camshaft isn't large enough to retain upper rpm performance.
The valve springs are weak or not matched to the cam.
The timing chain is excessively worn.
First thing I would do is convert it to a HEI. the best place for points is the trash. Once you know it's getting enough spark, then you can move on to the next steps to resolve the issue.
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Old 07-23-2012, 08:57 PM
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I forgot to mention this is a stock smogger 455 so there is no big cam or anything. The only performance part on it is the carb. I would like to switch to hei but the points are new and set up right so i dont think they are the issue, but anything is possible.
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Old 07-23-2012, 09:02 PM
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New points or not, they or the coil may not be up to the task at higher rpm's. At what point (rpm) does it quit making power?
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Old 07-23-2012, 11:06 PM
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If you convert it to stock HEI,then you will need to upgrade the coil.Curious why you put a 750 x onit? what was wrong with the Q-jet?
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Old 07-24-2012, 04:48 AM
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I dont have a tach hooked up but it feels like its breaking up around 2500 rpms, maybe 3000. The reason fo the holley is i got the motor without the carb and the holley was given to me.
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Old 07-24-2012, 05:13 AM
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it this a new issue? did it do it before the installation of the new fuel pressure regulator?
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Old 07-24-2012, 05:28 AM
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It did it before the reg and doesnt change with pressure adjustment. im not familiar with holleys, could it be a power valve?
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Old 07-24-2012, 04:25 PM
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Ok so i pulled of the dizzy cap and when i turn the crank there is about 6 degrees of crank rotation before the rotor turns.do i have a stretched timing chain?
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