Motor runs good at mid and low rpm but bad on high rpm

« **on:** September 20, 2014, 12:59:48 PM »

Ok people this is my first post so hang in there. I had a 455 olds motor rebuilt, the old motor ran ok with the edelbrock 750 marine carb and stock coil/dist but on the new motor it runs good at mid and low rpm but nothing when i mash down on the gas, i cant even mash down right out of the hole, i have to slowly ease in into the throttle.

ANY SUGESTIONS

« **Reply #1 on:** September 20, 2014, 01:08:53 PM »

While the motor was rebuilt , where was the carb??? Was it rebuilt also???

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« **Reply #2 on:** September 20, 2014, 03:41:36 PM »

Quote from: Relaxin Jackson on September 20, 2014, 12:59:48 PM

Ok people this is my first post so hang in there. I had a 455 olds motor rebuilt, the old motor ran ok with the edelbrock 750 marine carb and stock coil/dist but on the new motor it runs good at mid and low rpm but nothing when i mash down on the gas, i cant even mash down right out of the hole, i have to slowly ease in into the throttle.

ANY SUGESTIONS

Check to see if your accelerator pump is working and verify you are actually getting wide open throttle( with the engine off)

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« **Reply #3 on:** September 20, 2014, 10:53:31 PM »

Quote from: Relaxin Jackson on September 20, 2014, 12:59:48 PM

... the new motor it runs good at mid and low rpm but nothing when i mash down on the gas, i cant even mash down right out of the hole, i have to slowly ease in into the throttle.

Going to need a little more information even to make a good guess.

What is it doing when you get near full throttle? Does it just stop pulling rpm, does it backfire or sputter?

What does it do when you try a hard acceleration from stop?

At what rpm does it start to act up?

« **Reply #4 on:** September 21, 2014, 02:12:47 PM »

Over the years have had a number of OLDS and on one of them I had a similar issue. Turned out to be voltage - too weak - new battery and cleaned up the ground on the block - got my spark back to 100%

Relaxin Jackson

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