I just replaced my Edelbrock carb with a 650 DP Holley carb. I'm using a 2" open plenum between the intake and the carb. I'm getting a stumble, especially with the engine cold. A friend told me that Holley's are more sensitive and the increase volume of intake will cause the stumble? I was advised to increase the discharge nozzles from .28 to .31. or remove the 2" spacer and go with a 1" spacer. Any recommendations? I've already adjusted the carb, accelerator linkage, cam, etc. It's on my 289. I'm also running an Edelbrock aluminum intake.
I would remove the open spacer and bolt on a 4 hole or super sucker spacer. Open spacers are for high RPM power at a sacrafice of low end torque. So when you add a 2 inch spacer you need more fuel discharge to get the stumble out so to use it, you`d have to go up on the shooter size until it`s gone. I would also check the accelerator pump, it must shoot fuel the instant you move the throttle, if it don`t it`ll stumble.
I removed the 2" spacer which was open and replaced it with a 1" spacer which has the holes (super sucker). Very big improvement on the stumble and hardly any at all. I may have to check the float levels again and it appears the rear linkage has some play in it for the secondaries. I retarded the timing slightly and it appears I may have to advance it a few degrees again. It's odd, the edelbrock actually drove nicer with the 2 inch spacer on it. I always had a flat spot on the highway which the spacer got rid of. I had the 1" already, so it made it convenient to change the two out. Thanks for the helpful advice. Maybe this will help someone else as well. :thumbup:
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