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Its a 1973 351C in my mustang..........got a new carb because the old one wouldnt respond to the mixture screw adjustment........anyways.........i took off the egr plate and put a spacer in its place.........now the engine wont rev and stay running...........if i rev it high enough........it dies when it comes back down.........could it be the carb?(which is about 2 years old now).......maybe a bad power valve perhaps?..........or could it be a vacuum leak somewhere?.........any suggestions would be greatly appreciated..THANKS
 

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Sounds like a leak. Get out the carb cleaner and see if you can locate one.
 

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EGR Plate

Doc here:pimp:

Why did you put a spacer plate on the EGR? Are you still running an EGR Valve?

If so, It Sounds like it has a BIG leak, or it's holding wide open at idle.

Try Disconnecting the Vacuum line to it and plugging it. Then see if it idles.

If you are no longer running an EGR, take the spacer plate out, install a new gasket and sealer, and put the block plate back on without the spacer.

Doc :pimp:
 

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aka Duke of URL
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The OEM intake manifold and EGR spacer are a matched set on the 73 351C. The manifold has to have that matching spacer. The 4300 MOTORCRAFT was a spreadbore, correct? Either you need to find a pre-1973 intake (squarebore) or go aftermarket (or if you are short of funds...TRANS-DAPT makes a carb adaptor that will allow you to use a squarebore on the EGR spacer).

If you look at the bottom of the spacer and the inlet in the carburetor pad, you will see the source of the massive vacuum leak.
 
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