Good news and bad news for the MGB idle problem
Posted By RichC on September 28, 2011
So much for the carburetor tuning and electrical issues that have frustrated me lately (posted yesterday) … it wasn’t the problem. Can you tell what the problem is from this photo?
I’ve been struggling to figure out why the 1975 MGB would not run smoothly at idle … now I know … the problem is the #2 cylinder’s intake valve. The sticky valve didn’t show up immediately after I took the engine apart and installed a new cam … or when I adjusted the rockers and tweaked them for a second time. I just so happened that the valve spring returned the valve back to a resting closed position each time I worked or looked at it. The initial compression test showed all cylinders with compression and #3 and #4 slightly higher at about 110 psi. BUT after rechecking tonight, I noticed something odd … zero compression in the number 2 cylinder? Hmm … a stuck valve?
After popping the valve cover off I didn’t immediately see the problem; the spring returned the valve to it’s closed position again. It wasn’t until I cranked the engine a couple revolutions that the intake valve on #2 opened and eased S-L-O-W-L-Y closed again. After a quick crank again, it stuck open for a few more seconds, enough for me to snap the above photo. AHHH … the culprit!
Unfortunately the MG will be sitting for a week or so before I pull the head. The next few days are travel oriented and then we have my nephews wedding this weekend. (Congratulations Ben and Emily … a happy time)
To be continued.
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