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September 29th, 2008

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Q & A: MGB Engine Restoration

Thursday January 08th, 2009
Q & A, MGA, MGB, MGC, MG T-Type, Midget
I have a ’71 MGB with 18GK engine that was put away in a shed for about 25 years. The engine was overhauled to some degree sometime before it was parked in the shed. No special preparation for storage, other than draining the cooling system, appears to have been done. The owner had considered restoring it himself and did replace rotors, pads, drums, shoes, wheel cylinders, clutch cylinders, and a few sundry parts before deciding to let the project go to the highest bidder …….. namely me.



The engine had not been run for 25 years, so I did a compression check and found #4 cylinder near 0 psi. I decided that it would be best to pull the engine/transmission and thoroughly examine the internals since it was likely parked for 25 years with old, dirty oil in the crankcase. I found the cam and crank in very good condition, but the bearings show what I believe is deterioration from acids in the old oil (flaky, spotty, blotchy appearance).



My main concern at this time is whether I should rebore the block since the piston skirt to cylinder wall clearance is about .004 inch. I think the spec is more like .001 to .002 inch. Is that correct? Do I need to have the cylinders bored out and install new pistons? I’ll probably never drive the car more than a few thousand miles a year, if that much.



The low compression on #4 cylinder was due to a rusty exhaust valve and seat. The exhaust valves in particular show wear from the valve seats. Is it best to have hardened seats and stellite exhaust valves put in now or would a simple regrind be sufficient for a car that will only be driven a couple thousand miles a year?



In the end, I still want a dependable engine, so I’m not afraid to invest what’s necessary. What’s the best way to go here?

All engine work is expensive, so my approach is to make the engine run first, take it on a long drive and then rate the engine by these four considerations: compression; oil pressure; oil consumption; camshaft condition. Had you started it up, y... read more