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MG MGB Technical - Engine Rebuild

Hi Everyone,

To update anyone who remembers my previous post, my '69 MGB-GT which I recently put back on the road after sitting in a field for 8 years is still burning oil fairly bad. The two center plugs were very black for a while, after I got it on the road, like I may have had stuck oil rings. Now about 1000 miles later, all the plugs are caramel colored and it doesn't burn oil as bad but the plugs get a buildup on them. Its not black, its crusty and caramel colored. I assume it is still a function of the burning oil. Compression on all cylinders is between 135 psi and 145 psi. Is it time for a rebuild or is there something else I'm missing? Crankcase ventilation is through the carbs. Hoses look good but I haven't checked operation of this system closely. To check it should I just pull the hose loose from pushrod cover on the side of the engine and see if there is suction on the carb. side?
Paul S. Canup

Try this: with the engine at idle remove the oil filler cap and place a small piece of paper over the opening. The paper should be just big enough to fit, but not get sucked in. With a properly functioning PCV system the paper should be held against the opening by vacuum and the engine rpm will drop. If you have piston blow-by it will push the paper off, although dont confuse it with the fan wash.
The caramel color sounds OK, but perhaps the "crusties" are from fuel additives. Try another brand (say Sunoco 94). Is your air pump still working or installed? I also have a 69MGB and the PCV system is pretty simple, as long as the hoses are in good condition.
Andrew Blackley

Hi Andrew and everyone,

Thanks for the good information. I'll try that process with the paper in the next few days. I'm hoping it my be as simple as putting on new hoses but I'm not getting my hopes up.

I've had the car since '73 and the air pump system was not working then, and I have never repaired it. We do not have emissions checks here yet so I havn't repaired it but would like to at some point.

If I decide to rebuild the engine it seems the pistons and rings are one of the critical components of a rebuild. Is there any particular ones to stay away from in doing a rebuild? You are welcome to email me if there is a specific brand you've had bad experiences with. How about rebuild kits? Are they a good way to go?I just want to make sure I use something reliable.

Thanks,
Paul
Paul S. Canup

Paul, sounds like things are ok with the engine. the compression is good and close enough that I would say the rings are ok and if plugs are not oiling up you are not getting oil past them. I would not worry about a rebuild yet.
On the subject of the air pump and PCV valve. I have a '69 also and took off the air pump and plugged the injector holes and have been running the car with out air injection since about 1978. I found the cam shaft is the same as the earlier cars and thus did not have to change any timing of the distributor. The car at the time continued to pass our smog inspections. I was relieved two years ago, after rebuilding the engine that my car became exempt from the current regulation. Though here in California that may change again! California requires a visiual inspection to varify equipment is in place so I was glad I didn't have to reinstall the pump and injectors.
By all means hang on to that air pump and if you can, get it serviced just in case. Replacing the rotor vains may be all it needs. They are a rare item to have to find when in need.
Cheers
Geoff Kimler

This thread was discussed between 28/01/2003 and 29/01/2003

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