If i was to put a squarebore edelbrock performer series carb (ex. 600cfm) on a spreadbore manifold, should it run like crap or not make a difference? The spreadbore has the bolt holes so it bolts right up. Theoretically, lets say i already tried this, and the plugs foul out. Did the difference cause this?

 

Not sure if it would cause your plugs to foul...I suppose it could. They sell a squarebore to spreadbore adapter you can use to mount the carb to that intake...not real expensive either. You may want to look into that.

 

It will work fine if you remove the divider holes O O { | }
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This way the the throttle blades can acutually open up if you dont they will not open and foul the plugs. I did this to my lg4 manifold. It basicly makes it like any other replacment manifold minus 4 extra mounting holes.

 

By this, I assume you mean "the spreadbore manifold", meaning it's an aftermarket manifold.

I'm running a squarebore Holley on an Action+ manifold that has both the spreadbore and squarebore patterns drilled/tapped in it. I had an adapter on it for the last half of last season, took it off this spring and don't regret it. The extra height did nothing for me.