Hi new to group, looking for some advice. I have a 1968 289. Purchased car stock, apart from some kind of mild cam upgrade, original cast heads etc, went ok I guess, but didn't think it was imo fast, so I thought to get a head upgrade, so purchased a pair of pro comp heads, now I know they have had some bad reviews, but on inspection I can't see anything wrong with them, all valves seating and lapped in nice, no leakage. New heads: 2.020in intake valve, 1.600 ex valve running off edelbrock performer 289 manifold, 4 barrel edelbrock carb, which were already on engine. Set all valve preload all new gaskets, fired up first time, now hears the BUT, it ticks over lumpy, and is now worse than original cast heads, re performance, racking my brain as to what's going on, only thing I can see is head intake ports are bigger than manifold ports, but with it being small to large, would this cause a problem? Any thoughts advice, please throw my way, stripped top off twice now, costing fortune in head gaskets. Thanks.

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