Blue Smoke

I have a problem with my 76 MGB. I've had it about a month - we were driving a week ago, and it started running really rough. When I got it home, I tested for bad gas. and for vacuum leaks. It was still running rough - I thought the engine was going to jump out. I finally decided to change spark plugs ( I had changed them just after I bought it) and it smoothed out. I took it down the street, and everything seemed fine for about half a mile, and then I started loosing power, and spewing blue smoke behind.

Now, I can't get it much over 35 mph, or 2500 rpm. Oil pressure is still fine, and it runs cool. I'm going to do a compression test this weekend, but I was hoping someone could give me some hope - I'm afraid I'm looking at a complete engine rebuild, which will cause me to park it for several months, just as the weather is clearing.

Thank you for your help!

Does your car still have the emissions equipment and the ZS carburetor? If you are running a Weber downdraft carburetor how is the crankcase vent hooked up? Go ahead and run the compression check, you need that information but it sounds like your crankcase vent may be hooked into the intake manifold. That could cause the problem you have.

Thank you! I'll check. I still have the Zenith carb, and I think all the emmisions stuff is there. It was running fine, but I'll get my Bently manual out and make sure how everything is suppose to be hooked up while I'm running the compression test.

I wanted to give the resolution of my problem here - I actually received the answer at the MGOC bulletin board.

It turned out to be the diaphragm on my Zenith carburator - a $5 fix. You can see the full post at http://www.mgcars.org.uk, under their bulletin board - its posted under in the MGB Technical section, under the title "76 MGB - Very Rough Idle"

Thank you for all your suggestions!