SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: Relaxin Jackson on September 20, 2014, 12:59:48 PM

Title: Motor runs good at mid and low rpm but bad on high rpm
Post by: 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       :screwy:
Title: Re: Motor runs good at mid and low rpm but bad on high rpm
Post by: mobboss 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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Title: Re: Motor runs good at mid and low rpm but bad on high rpm
Post by: JBASHAM on September 20, 2014, 03:41:36 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       :screwy:

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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Title: Re: Motor runs good at mid and low rpm but bad on high rpm
Post by: crewchief22 on September 20, 2014, 10:53:31 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?

 
Title: Re: Motor runs good at mid and low rpm but bad on high rpm
Post by: socaljst1970 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%
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