MGB rocker cover pressure
Discussion
Hi,
About a month ago I bought a standard 1978 MGB, I have noticed that it uses a lot of oil and blows smoke under heavy acceleration but not when cruising at steady speeds. I should mention the engine was rebuilt about 500 miles ago and produces 94bhp on a rolling road. This evening I noticed that if I remove the oil filler cap with the engine running the tick over increased and the engine runs much smoother and if you place your hand on the filler you can feel the engine sucking your hand to the rocker cover. At this point I started to rev the engine and notice that without the cap the engine was not smoking when revved. Replace the cap and the tick over drops engine runs rough and starts to smoke when revved. question is does this point to worn valve guides ? is the engine sucking oil into the cylinders due to the increased negative pressure with the oil filler cap in place ?
Any thoughts or advise ?
Many Thanks
About a month ago I bought a standard 1978 MGB, I have noticed that it uses a lot of oil and blows smoke under heavy acceleration but not when cruising at steady speeds. I should mention the engine was rebuilt about 500 miles ago and produces 94bhp on a rolling road. This evening I noticed that if I remove the oil filler cap with the engine running the tick over increased and the engine runs much smoother and if you place your hand on the filler you can feel the engine sucking your hand to the rocker cover. At this point I started to rev the engine and notice that without the cap the engine was not smoking when revved. Replace the cap and the tick over drops engine runs rough and starts to smoke when revved. question is does this point to worn valve guides ? is the engine sucking oil into the cylinders due to the increased negative pressure with the oil filler cap in place ?
Any thoughts or advise ?
Many Thanks
possibly - change the oil filler cap to the black plastic filtered and vented £4 from MGOC Spares £11 from some other suppliers for the same cap - MGOC Spares - Oil filler cap (vented) - Black GFE6003
lesson one bling's usually for show not go!
also check that the breather hoses aren't blocked or collapsed but it doesn't sound like they would be, there's a John Twist video telling you how to check this
you need to put more miles on the engine and do an oil and filter change to whatever are the engine builder's requirements
if you've got a bright red painted MGB, especially if it has chrome wire wheels, then you might need to check a lot on it as they're usually for show rather than go
anyway, should you really be driving a MGB this late in the year, no wonder you have problems!
soon be SORN time
ETA: check any plates or seals that the breather pipe comes from for security and sealing
lesson one bling's usually for show not go!
also check that the breather hoses aren't blocked or collapsed but it doesn't sound like they would be, there's a John Twist video telling you how to check this
you need to put more miles on the engine and do an oil and filter change to whatever are the engine builder's requirements
if you've got a bright red painted MGB, especially if it has chrome wire wheels, then you might need to check a lot on it as they're usually for show rather than go
anyway, should you really be driving a MGB this late in the year, no wonder you have problems!
soon be SORN time
ETA: check any plates or seals that the breather pipe comes from for security and sealing
Edited by nta16 on Friday 29th August 09:41
Had a similar issue on my 'C' earlier in the year. Coincidentally it also has a fancy alloy rocker cover and cap. On investigation it was found that the crankcase breather had been cobbled up and was not releasing pressure fully. My solution was to vent to catch tank and filter. All's well now. Good luck and enjoy it.
if you've got a bright red painted MGB, especially if it has chrome wire wheels, then you might need to check a lot on it as they're usually for show rather than go
anyway, should you really be driving a MGB this late in the year, no wonder you have problems!
soon be SORN time
ETA: check any plates or seals that the breather pipe comes from for security and sealing
Edited by nta16 on Friday 29th August 09:41
[/quote]
very funny ha ha
woodytype S said:
nta16 said:
if you've got a bright red painted MGB, especially if it has chrome wire wheels, then you might need to check a lot on it as they're usually for show rather than go
anyway, should you really be driving a MGB this late in the year, no wonder you have problems!
soon be SORN time
ETA: check any plates or seals that the breather pipe comes from for security and sealing
very funny ha haanyway, should you really be driving a MGB this late in the year, no wonder you have problems!
soon be SORN time
ETA: check any plates or seals that the breather pipe comes from for security and sealing
woodytype S said:
if you've got a bright red painted MGB, especially if it has chrome wire wheels, then you might need to check a lot on it as they're usually for show rather than go
anyway, should you really be driving a MGB this late in the year, no wonder you have problems!
soon be SORN time
ETA: check any plates or seals that the breather pipe comes from for security and sealing
very funny ha haanyway, should you really be driving a MGB this late in the year, no wonder you have problems!
soon be SORN time
ETA: check any plates or seals that the breather pipe comes from for security and sealing
Edited by nta16 on Friday 29th August 09:41
Shaun,
glad to help, and thanks for reporting back
most owners won't believe that a plastic part can be as good as a shiny bling part or make such a difference but I was told it many years ago
that plastic part could last you decades, if towards the time the engine starts to need another rebuild you can even clean the plastic cap - or buy another
glad to help, and thanks for reporting back
most owners won't believe that a plastic part can be as good as a shiny bling part or make such a difference but I was told it many years ago
that plastic part could last you decades, if towards the time the engine starts to need another rebuild you can even clean the plastic cap - or buy another
Edited by nta16 on Tuesday 2nd September 21:34
some bling caps might be better than others but the black plastic filtered and vented oil filler cap seems the best to fit most often
checking covers and pipes was suggested
OP changed to the black plastic filtered and vented oil filler cap and felt that this resolved the problem, in this case black plastic filtered and vented oil filler cap 1, bling cap 0
checking covers and pipes was suggested
OP changed to the black plastic filtered and vented oil filler cap and felt that this resolved the problem, in this case black plastic filtered and vented oil filler cap 1, bling cap 0
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