i have a 66 coupe .. when i bought it, it had a 2bbl carb and intake on it however i changed it to a 4bbl intake and carb. the problem is, ever since i made the conversion my engine has been missing terribly. i pulled one of the spark plugs out and it had carbon all over it so it was definitly not firing but could the 600 cfm carb be to much and if so what 4bbl carb should i put on it...is it running a to rich of a fuel/air mixture. thanks for all replies

 

it could be,,,,spark plugs,,,,wires,,,,or carb..change plugs first and see thats the cheapest way ,,unless you need wires anyway are they old???could be carb,,blown power valve???just work your way up to the carb..let us know your results...

 

Did you install a bigger cam? If not you are over carbed. Also check firing order.</P>


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I would double check the torque on the intake manifold bolts as you may have a vacuum leak, causing the miss. Also check the carb to manifold for a vacuum leak in that area.

 

I'm looking at a 670CFM for my 65. The street avenger Holley carb. thats for 300-400 HP. I have mods and stuff so I know i'm over 300. But I think that 600 you have would be okay..

 

just wondering what mods you have other than what you have listed in your signature? because with a cam and headers you're not going to be getting 300hp out of a 289 without it being a serious cam and not streetable or with fuel injection or something. we've got a 4bbl carb, headers, cam and true duals and it's probably putting out 250hp on regular pump gas, the rear gears really limit it though, but with the 3 speed auto we should probably keep the gears...

 

Carbon buildup does not necessarily mean it is not firing. An easy way to check that is to remove the plug. Put the spark plug wire back on the plug and hold it with an insulated pair of pliers. Then roll the motor over..look for the spark. If you have no spark or a weak spark, do the same thing with the wire coming off the coil to the center post on the distributor cap. Grab it with an insulated pair of pliers, and hold it about an inch above the center post. of the distributor. You should see a spark (be careful not to get to close to a ground cause it will ZAP you). If again you see a weak spark your coil may be going away.

Ron