LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

hit 2nd instead of 4th now motor stumbles

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Old Aug 5, 2004 | 08:18 AM
  #1  
kochisp's Avatar
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From: Lk. Orion, Michigan
hit 2nd instead of 4th now motor stumbles

This is the only thing I can think of that would be the point when it seems my car took a dive in performance. I had the motor rebuilt last fall, about 12k ago. For about 11k the MAF was on backwards. I always thought it was running so rich because of the cam. I got it dyno tuned at AP Engineering. They discovered the MAF issue and turned it around. Before they turned it they couldn't even hardly get a horse power baseline. Then after turning it the got a 325hp baseline. Then they tuned it to 342hp. After that it ran really strong. Within a week I broke a rocker stud, so I put arp studs in. Then the 2nd instead of 4th happened. I sent one of my comp r lifters up a little to high and bent the retainer, (that big spider looking thing), and it turned the comp r sideways. I bent it back and put the stock lifters back in. It seems to run worse the longer it runs. Last night I replaced the opti by the way. Any ideas on what to do next.
Old Aug 5, 2004 | 08:45 AM
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Re: hit 2nd instead of 4th now motor stumbles

Maybe you should have just continued your other thread. I would be checking all the pushrods for straightness.
Old Aug 5, 2004 | 09:42 AM
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Re: hit 2nd instead of 4th now motor stumbles

The pushrods seem to be straight, I was thinking maybe the springs could be failing.
Old Aug 5, 2004 | 10:07 AM
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Re: hit 2nd instead of 4th now motor stumbles

I've had the exact same thing happen before. A mechanical over rev situation is pretty destructive to your valvetrain components. The time when your comp-r lifter was in the bore sideways probably ruined your cam, and that lobe is probably getting worn away now, hence the miss. JMO, it's what happened to me.
Old Aug 5, 2004 | 11:43 AM
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Re: hit 2nd instead of 4th now motor stumbles

How quickly would the cam get ruined. I didn't put many miles at all after the lifter issue.
Old Aug 5, 2004 | 02:27 PM
  #6  
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Re: hit 2nd instead of 4th now motor stumbles

It also seems strange that it starts to miss on accelaration only after it is at normal operating temp
Old Aug 5, 2004 | 03:10 PM
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Re: hit 2nd instead of 4th now motor stumbles

when my rocker arm turned sidewise i didn't drive it but less then 3 miles and it ruined a couple lobes on my cam...really crappy deal, looks like custom cam time! i know i did
Old Aug 5, 2004 | 03:25 PM
  #8  
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Re: hit 2nd instead of 4th now motor stumbles

I really hate to hear that. This is terrible timing, woodward cruise is like weeks away.
Old Aug 5, 2004 | 03:28 PM
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Re: hit 2nd instead of 4th now motor stumbles

well you better get moving!
Old Aug 5, 2004 | 04:33 PM
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Re: hit 2nd instead of 4th now motor stumbles

Originally Posted by kochisp
How quickly would the cam get ruined. I didn't put many miles at all after the lifter issue.
The cam would be ruined instantly. Think about how the lifter was riding on the cam (sideways).
Old Aug 5, 2004 | 05:00 PM
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Re: hit 2nd instead of 4th now motor stumbles

If you think you have a cam lobe or lifter problem, use a dial indicator and compare the lift of the suspect one with one that was not damaged. Be sure to compare intake to intake or exhaust to exhaust.
Old Aug 5, 2004 | 06:47 PM
  #12  
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Re: hit 2nd instead of 4th now motor stumbles

Thanks shoebox, I was planning on sticking my finger in there but I really wouldn't even know what to feel for except a torn up lobe. One question though shoebox, why does it only run bad when hot?
Old Aug 5, 2004 | 07:05 PM
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Re: hit 2nd instead of 4th now motor stumbles

Originally Posted by kochisp
Thanks shoebox, I was planning on sticking my finger in there but I really wouldn't even know what to feel for except a torn up lobe. One question though shoebox, why does it only run bad when hot?
Don't know, just trying to give you a way to eliminate possibilities.
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