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MGB 79 MGB Head Gasket Screwup


Freshman Member
All Input Welcome:

Problem: Water consumption 220 miles after engine “freshening”
New bearings, camshaft, rings. Block only cleaned and honed. New exhaust valves. Carb rebuild, New hoses. That’s about it. Project rebuild on a budget.

What I am proud of:
It ran pretty well for 220 miles. It had a very smooth idle and ran as strong as can be expected. I followed rebuild instructions and re-torqued head after 100 miles. It was a good fun car project with my daughters.

What I am not so proud of:
I did not have the block machined.
I did not have the head machined.
I did not replace Head Studs.
I coated the head gasket with Copper Spray-A-Gasket as recommended by somebody. During this process the gasket got dirt on it when the spray gasket was wet. I was not sure how to clean the dang thing so I decided to put it on anyway.

What it looks like now:
It was apparent after the head was removal that water is getting into the #2 and #3 pistons. The attached pictures show the story.


As a side note, the pistons look awfully sooty to me for only 200 miles. It did not seem to be running rich and the plugs looked good.

So who among those more experienced then I, can chirp in with a guess at the most likely source of my problem. Can the recommended path forward not include an engine removal? Should I just buy another gasket and try not to drop the @%$# thing on the floor when it is wet with the spray gasket stuff? Should I even use that stuff? I am thinking of taking the head to a machine shop to check for flatness. Any helpful advice is welcome.


Jedi Knight
I do not use any spray sealers just a good quality gasket. The thing to check is if the head is cracked and then if its true and flat. If thats good then get another gasket and see what happens. Be sure to clean the head and top of the block good so there is no sign of that spray on sealer. Bob


Great Pumpkin
Country flag

On the later heads, there was a propensity for #3 to develop a crack twixt water galley and intake runner. A pressure test will find that. If no crack, have it checked for warp. Most likely is that the gasket didn't seal well, from your narrative about the spray and the "FOD".


Freshman Member
Thanks for the feedback guys, that was just what I was hoping to hear. What do you think on the block cleanup? Scotch-bright and some solvent? I guess I need to be super careful about what might end up in the crankcase.


Country flag
Put grease around the edges of the pistons between piston and liner, that way if anything falls in the cylinders it will catch in the grease rather than between the piston and top ring, vaccum the loose debris from the top of the pistons and you can scrape most of the grease out with a plastic spatula or other appropriate tool before you refit the head. The debris that goes to the edge of the cylinders will of course be trapped in the top of the grease


Freshman Member
As it turns out, it was not as much my bad assembly technique as it was a bad cracked head. What is puzzling is that it seemed fine before I freshened up the rest of the engine. So I have found another used head that turned up to have cracks also. Are all old cast heads this fragile? There is another guy ready to sell me a used head for under $400 that is guaranteed not to be cracked but I am wondering if it is worthwhile to drop the $950-$1300 for a new alloy head. This project was supposed to be low budget but I really want to be done with the head stuff. If an old cast head is good and I keep it from overheating will it not crack?
The last MGB heads, the CAM1106 was prone to crack, worse one fo the bunch, if you go for the new head, i would go for the cast iron head, it a little better quility than aluminum head, I installed several of them and never had issue with them.


Jedi Knight
I have a extra late MGB head that has been crack tested and is a good core. Let me know if you still are in the hunt for one. Bob
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