On my '93 318, cylinders 1 and 7 were not firing. I removed the valve cover and cylinder 1 and 7 intake rockers were completely broken off! Now these are the stock stamped rockers being driven by a .512 lift cam and held back by stiff RT springs. Perhaps these rockers simply couldn't can the pressure? Any other ideas why these would fail?
Also, a compression test showed zero compression on those two cylinders. Since the valves where the broken rockers are located are always closed, shouldn't I have seen full compression on those two cylinders? Or is zero compression normal for broken rockers? Can a stuck closed intake valve cause it to burn and have no compression? However there was no fuel entering the cylinder with the intake valve stuck closed so it couldn't burn, right?

I have already have a set of roller rockers on hand that I was going to use for my 408 but not sure if I should install them and call it good or completely remove the head (lot more work...).

Thanks for any suggestions!

James

 

First of all, with that cam you shouldnt have even used those rockers period. Second the cylinder will not fire at all if the intake valve doesnt open for fuel and air. As for the compression in those 2 cylinders,since the rockers are not working then you wont have air to compress because there is nothing being drawn in by atmospheric pressure do to mechnical failure. Thus -no compression. Take the head off and look at everything, and be smarter next time you run performance parts with performance parts &not stock parts.