Jul 112019
 

1973-ford-mustang

I have a 1973 302 V8 with an updated 4bbl intake manifold and carburetor. I was hearing a knocking sound in the engine and took the valve cover off. The number 2 exhaust valve retaining rings were in shambles and the rocker was loose as well. I found and removed all the broken pieces and ordered a new valve seal and retaining clips. Was able to compress the spring with a tool and seat the new clips however I am unsure if I got them on the the lip of the valve shaft but they held so I assume that they caught. Next I checked the pushrod and isn’t bent and put the rocker assembly back on the way I took it off. There was a little play in the rocker arm but my dad manually turned the engine and as it cycled through the stroke it tightened.

Knocking sound in the engine

Then I put the valve cover back on and turned the engine over but was hearing a clunk clunk and just all sorts of rough noise coming from the passenger side ( the side I was working on.) I’m wondering what the heck is the problem. I think it might be because that cylinder wasn’t being used for so long that there is just crud in there? Next I removed the spark plug wire and tried again but the same noise came. Then I didn’t attempt to start it further. Is the timing off now that there is another valve in play? Could I not have set the lash correctly on the valve stem? The spring didn’t shoot off lol although it did hit me in the junk when I had it in the spring compressor. Sorry lol if these are basic questions. Anybody got any advice?



You can remove the spark plug and spin the engine over to clear the cylinder if you deem it full of oil. You would want to perform a compression test to confirm no internal damage was done when the valve dropped. The valve may be bent if it was hit by the piston. This will show up as low to zero compression on the gauge.

On stock ford engines you just tighten the rocker so no worries about valve lash. This would be different if aftermarket heads were installed. That being said, having loose rocker on stock head would also point to a bent valve. This would create a loud popping out the exhaust as the exhaust valve would be stuck open when the engine fired that cylinder.

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