High RPM stumble
08-31-2010, 10:45 PM
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High RPM stumble so.. after rebuilding the engine and finishing my break-in miles i got in the throttle to see what it was gonna do. It pulled dang hard and then got up in the rpm's and started stumbling. It does it anywhere in the rpm's over 4k.
It was bored .020 over. Mild head work. cc503 cam w/1.6 rr's.
I still have the stock injectors and the tune is still mostly stock as far as the timing and a/f tables go. (Have not had a chance to get it re-tuned)
My opti is not a factory ac delco. yes it was an ebay purchase a long time ago to keep on the shelf if my old one ever quit. In looks it is very similar to my friends chandler opti.
Before rebuilding the engine entirely I had done just the cam swap. I used the same opti that is on it now and still with stock injectors and it did not do this.
It has new 8.5mm plug wires, new autolite plugs gapped at .035.
So.. could it be that the stock injectors could handle just the cam swap but not the 3 more cubic inches and head work?
Could it be the opti even though i ran it previously and it worked fine?
Someone also mentioned my valve adjustment being too tight. (I used the ECIO method and set them to 1/2 turn past zero lash according to machine shop.)
I'm waiting on a new cable so I can datalog and hopefully help pinpoint the problem.
But until then..Any other ideas before dropping $300 on new opti or injectors?
It was bored .020 over. Mild head work. cc503 cam w/1.6 rr's.
I still have the stock injectors and the tune is still mostly stock as far as the timing and a/f tables go. (Have not had a chance to get it re-tuned)
My opti is not a factory ac delco. yes it was an ebay purchase a long time ago to keep on the shelf if my old one ever quit. In looks it is very similar to my friends chandler opti.
Before rebuilding the engine entirely I had done just the cam swap. I used the same opti that is on it now and still with stock injectors and it did not do this.
It has new 8.5mm plug wires, new autolite plugs gapped at .035.
So.. could it be that the stock injectors could handle just the cam swap but not the 3 more cubic inches and head work?
Could it be the opti even though i ran it previously and it worked fine?
Someone also mentioned my valve adjustment being too tight. (I used the ECIO method and set them to 1/2 turn past zero lash according to machine shop.)
I'm waiting on a new cable so I can datalog and hopefully help pinpoint the problem.
But until then..Any other ideas before dropping $300 on new opti or injectors?
09-01-2010, 10:15 PM
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I forgot to mention that my compression is pretty much stock 10.5:1
could my plug gap be too tight (.035) as blackbird87 suggested?
*when it was just the cam swap i had them gapped at .045
could my plug gap be too tight (.035) as blackbird87 suggested?
*when it was just the cam swap i had them gapped at .045
