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  #1 (permalink)  
Old 10-09-2006, 09:46 AM
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Cobra Make, Engine: SPF1715, Roush Built 434 ci Stroker, Dart Block, Ported AFR 205 Heads... 561 hp / 547 tq, Former Roush Show Car, Completed and Prepped By Olthoff Racing.
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Default MSD Ignition Question

I have a Roush Small block stroker motor with an MSD 6AL ignition with a 6200 rev limiter chip. If I roll into the throttle the motor will rev to the 6200 limiter with no problems. If I go through the gears from a stop light which puts the motor on the limiter while the tires are spinning the motor will only rev to about 4800 rpms and sounds and feels like the limiter is kicking in. As I get Into higher gears and drop the rpms the motor still will only rev to about 4800 where again it feels like the limiter is kicking in.

Anybody have any ideas where to start looking for the problem? Could it be the chip, box etc...?
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Old 10-09-2006, 09:52 AM
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It may just be that your tach is not keeping up with the signal when the rev limiter is kicking in. If I get into first gear too heavy and bounce on the rev limiter it only shows about 5600 on the tach. If I approach it slowly is shows right at 5900 which is about where it should be.
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Old 10-09-2006, 10:36 AM
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I thought about that but you can definitely feel that the car is not pulling like it should through the gears. I can go through the gears all the way into 5th and still keep it on the limiter at about 4800 and the car just feels slugish at only about 120 mph. It is definitely a real problem because you can feel it and the mph are off from what it should be in each gear if it was actually reving to 6200. It's almost like the limiter kicks in and does not shut off when you shift to the next gear (gears)...
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Old 10-09-2006, 11:21 AM
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This occurs so quickly that sometimes it's easy to miss the obvious....Check the tach. Badger
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Old 10-09-2006, 11:56 AM
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You may be running the carb dry of fuel, check fuel system???
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Old 10-09-2006, 02:57 PM
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this happened to me. Replace the cheap fuel filter with a new cheap one. You'll be amazed how simple that was. Maybe?
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Old 10-09-2006, 03:07 PM
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You could always pull the chip out the MSD box
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Old 10-09-2006, 09:52 PM
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Your tach's out of synch. I had the same type of problem, Tack reading vs engine cutout. My tach was off by about 1K rpm, tried a different tach same make(SW) I borrowed from a friend...his unit read dead on, 56-5800 rpm it would cut out, the limit of the chip. My tach showed 4200-4600...hmmm
My friend tried my tach in his '65 mustang R clone..1K off when he hit the limiter.
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Old 10-09-2006, 10:47 PM
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This does not explain how you can sneak up to the 6200 limit on a lighter throttle opening, I like Rick & Ray think you might find your problem in the fuel supply, eg -line size, filter, tank vent,pump relief valve stuck partly open, small line fitting restricting flow etc.

Just had a thought,Is the MSD wired correctly, there was a problem where if the wires were reversed in the connector by people who thought they new better than MSD which plays havoc with the advance curve due to triggering off the back of the wheel, would have to read the article again.[ Circle Track ].

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Old 10-10-2006, 09:18 AM
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Thanks for the replies...

I changed the filter and the problem still exist. It does not feel like a fuel problem (to me) though, it feels like ignition to me. The MSD wiring has not been touched and the problem just started on it's own.

I was thinking it might have something to do with the spark advance Like Jac Mac said. I have a mechanic that is going to look at it, but all your help is appreciated and gives us some more ideas.

Thanks for the help.
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