QuestionQUESTION: I have a 1978 MGB, USA model. The previous owner took a rolling chassis and installed an engine he bought. He said it had a tag indicating late model MGB. After purchase I put it on a lift and noticed oil all over the bottom of the chassis from the engine to the transmission. After cleaning I noticed the hose to the breather on the front push rod access panel was pointing straight down toward the ground. I rerouted it up next to the valve cover and added a breather filter. The breather tube is blowing oil inside the engine compartment after long drives. A compression test shows 110, 105, 120 and 120 psi. This tells me I have pressure building up in the crankcase. For this reason I feel a rebuild is in order. Could this diagnosis be incorrect?
The plate on the passenger side under the head on the block is missing (although they were kind enough to leave the screws). The head has screws in the emission holes so I know it is late model but have no idea about the engine. It has 1800 on the drivers side and some numbers on the passenger side (12H3503) adjacent to the starter.
Is there a way to tell what I have without tearing down the engine? If not, what do I look for once I disassemble the engine?
Thanks in advance,
Peter
ANSWER: Hi Peter. All 1800 blocks are interchangeable, so stripping it down will not tell you much.
The compressions are all a bit low, but they are within 10% of each other, so there is nothing much wrong with the block, pistons, cylinder head or head gasket. Possibly you have an engine with a low compression head.
I really need more information to answer this question. Is there one carburetter or two? Has the car still got all its anti-smog equipment?
The Moss Motors website has a diagram showing what your engine compartment should look like.
http://www.mossmotors.com/Browse/PlateMenuProducts.aspx?WebCatalogID=8&PlateType
As you can see, there were 5 different layouts. If the engine has been changed it could be any one of them. Which one have you got?
Originally the breather on the front tappett chest went to a suction pipe on the side of the carburetter. If these have been changed, then it may need to be re-routed, but it should not go to the rocker cover without a gulp valve in line, and it should certainly not go down to the ground. If the carb has a pipe which is open, this will produce a very weak mixture and the engine will probably not want to start.
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QUESTION: Thanks for you reply. The car has a Weber downdraft, Pierce manifold and a header. All of the anti-smog equipment has been removed. There is a hole in the bottom of the air filter (which I assume is for the breather hose). If I was to put it in the bottom of the air filter wouldn't that channel oil into the carb causing gunking, etc.?
AnswerJoin the two together with an oil-tolerant rubber hose, but cut the hose in two and join the halves together with a rod through which you have drilled a 3mm (1/8) hole. Not wide enough to cause gunking, but enough to suck out some of the nasties.
By the way, remove the oil filler cap and wash it in a jar full of gasolene. The cap incorporates a small mesh filter that has a secondary breather function, so it must not get blocked.
