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1977 MGB

Last post 04-20-2010, 5:23 AM by PHIL WILKINS. 5 replies.
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  •  04-17-2010, 8:55 PM 23443

    1977 MGB

    Guys and Gals:

    I have a 77 MGB Roadster.  I did a complete restoration and when we started her up, ofcourse, she started first time.  I have a weber on her attached pictures.  Unfortunately, she is blowing blue at acceleration.  Nothing at idle.  Idle oil pressujre is 57 and at 2500 RPM 68-70.  That being said, she has only 30 miles on the engine, 20 over, new rings, new pistons, reground crank and cam, new water pump, new plugs, new leads all new bearings, new wiring harness and complete electrical (has anyone seen the movie the Madness of King George?).  Preliminary compression test gave me an average of 87 a little low I believe.  On removal of plugs they are dry, a little sooty. We took her out for 15 minute spins but still on gear change a puff of smoke blue not white.  The smoking has been greatly reduced from the first horrific notice, however, I am concerned it could be:

    A. Rings - hopefully not

    B. Valve guides - let's hope  

    Anyone have the answers or suggestions. The exhaust header is new and we fitted the stainless system from Moss.  The pipe does look a little black now.  I need someone to assist with the diagnosis if possible and ofcourse, the last thin we want is engine out.


    Paul G.

    Filed under:
  •  04-18-2010, 10:09 AM 23447 in reply to 23443

    Re: 1977 MGB

    hi.paul,from what you have written,i find it hard to comprehend why you would do all that hard work replacing everything,but not restoring the cylinder head as well.if all the bottom of the engine was so worn it needed replacing,how come the head  had no wear also.

    from my experiance,if you have replaced the rings/pistons then it will take a good few hundred miles on the clock before the engine beds in.during this time it will burn a bit of oil,getting less and less .i assume you are keeping the revs down a bit,to allow it to bed in.

    the valve guides will not suddenly start letting oil past,if its these at fault or the oil seals,they will have been worn like the bottom end and should have been replaced.

    the oil pressure is spot on.


    phil wilkins
  •  04-18-2010, 10:13 AM 23448 in reply to 23443

    Re: 1977 MGB

    Well, the compression might sound a bit low. Maybe Motorbill will come along to speak about that. With only 30 miles on a rebuild, I think you are way too early to start worrying about a little smoke or even compression until the rings get a chance to seat properly. Particularly since you said the smoking is "greatly reduced" I would suggest waiting for a few more miles to see if it continues to improve. What you have described seems pretty normal for a new break-in. Of course, we always want to pay closer attention with a new rebuild but watch more for sudden anomalies or gradual worsenings. As long as all seems to be getting better, you are probably on the right track.


    Never express yourself more clearly than you can think
    '48 Prefect
    '67 Sprite (project)
  •  04-19-2010, 7:35 PM 23475 in reply to 23447

    Re: 1977 MGB


     Thanks and you are probably correct.  Yes I ahve kept the revs under 3500 and I think we will drive her a littel more.  I would say teh smoke is down by 45% from teh orignal horror show.  My firs complete rebuild I have never even taken out a sparkplug, so I got teh book and went at it.  How do we post pictures do you know? I will drive her a little more and see what happens.

    I may take the head in also and get it checkcked through.  

    Thanka gain I will keep you posted.



  •  04-19-2010, 7:36 PM 23476 in reply to 23448

    Re: 1977 MGB

    Thanks for the re-assurance my first ever attempt or even build. I will keep you guys posted.



  •  04-20-2010, 5:23 AM 23477 in reply to 23475

    Re: 1977 MGB

    Hi.paul,I have been told a few times how to post pictures,but still cannot get the hang of it.your best bet is someone Like poolboy who's an expert at it,or christine at moss will help you. You did well with rebuild if you had not done much before. Good luck Phil
    phil wilkins