Symtom of rev limiter malfunction?

Old 05-31-2016, 03:25 PM
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Default Symtom of rev limiter malfunction?

I have a weird just off idle stumble on my 509 BBC with 750 double pumper. Starts fine, idles fine. As I start giving it throttle, it stumbles and farts a bit. Once past 3/8th throttle, it goes away and runs fine. Almost like it was getting too much fuel as the accelerator pump squirted fuel. Thought it was mis-cammed or mis-adjusted accelerator pump. Still there despite messing with it (changed from pink cam to orange cam). Am thinking I may be barking up the wrong tree and thought it may be ignition instead. Have a very old MSD 6A that MSD converted to a 6T 30 years ago. This conversion added a second box, which plugs into the 6T with a short cord. Into this second box is plugged the chips to limit the RPM. As the engine is brand new, I have not taken it to the 6000 RPM that is the current rev limiter chip to see if it cuts out. Thoughts? Thanks!
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Old 06-01-2016, 03:58 AM
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If it truly is getting too much fuel it will have a black puff. Does it do it rolling into the throttle slow or a quick hit? It's hard to tell by your description. My opinion would be that the problem wouldn't be at a point like you describe if it was a rev limit problem, but you could check by just pulling the limit chip I would think.

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Old 06-01-2016, 03:22 PM
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Most of the time a stumble is not enough fuel.
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