MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - correct valve cover

I'd like to replace the valve cover on my 79 engine wih an alluminum style cover to decrease the valve clatter and also since the old one is a bit beat up. My question is: do I have the original cover and should the replacement be the exact same? The current one is painted black, has no MG sticker on it, is vented with a hose to the charcoal cannister and has a vented oil filler cap. If I go to a new cover must it be vented? Am I supposed to have a vented filler cap also, it appears in the Moss catalog that I'm not, instead I should have the tight fitting cap. Thanks for the advice!
David Favero

Dave,

To be "correct", you need to have a valve cover that has a elbow pipe vent to the charcoal cannister and a non-vented cap. Your crankcase ventilation then runs from you foward side cover vent to the carb.

With that said, I'm using the polished alloy valve cover with the shiny, vented cap (has a hole in the center). With my last rebuild, things got a bit oily when she was being run in, however, they cleared up. I run the crankcase vent to the carb and then vent my carb float bowl down to the street (won't pass emissions like this, so what you do depends upon your requirements). Everything breathes pretty well...the charcoal cannister probably doesn't do all that much now (two out of three ports are capped, with only the port to the gas tank remaining), but the valve cover LOOKS great.

Now to my point...the alloy valve cover will not quiet your valve clatter noticeably. It does, however, look great. One could reasonably ask...why not just paint the old cover and save the $70.00? Save your plumbing (to the extent it still exists), as it doesn't hurt performance. No, I'm sure you'll do as I did, buy the shiny new cover...someday they'll come up with some sort of intervention program for those of us that just can't leave well enough alone...maybe not ;-)

FWIW,

Barry
Barry Kindig

When they come up with that "intervention program" for us incorrigible tinkerers, let me know, so that I can avoid it. ;-)
Bob Muenchausen

My engine vents from both the valve cover and the forward side (tappet) cover. Is both necessary? Could you eliminate one or the other and what are the effects if any? Thanks.
Brian

Depending on the year the carb applies vacuum to the valve cover vent and this is filled by air entering the vent on the tappet chest. Other years vent differently by the objective is still to get air flow through the crankcase. Blocking off either vent will stop that flow and cause condensation inside the engine, plus possible problems with fumes.
Paul Hunt

My guess is that you probably have an original valve cover, but that the stickers fell off when engine
heat took it's toll on the adhesive. The only way to confirm is to look at an illustration in a parts catalog
(ie: Moss, Victoria British, etc.).

I agree with Barry that an alloy valve cover does not reduce the valve clatter all that much - but it does
have some "...ohhh...ahhhh..." visual appeal whenever the hood is lifted.

Most alloy valve covers come with a vented cap and no ready provision to hook up to the charcoal canister.

Any vented cap has to be blanked-off for cars with closed crankcase venting systems. This method
will vary according to each model cap supplied with the valve cover.

A hole must then be drilled and tapped somewhere on the valve cover to accept a hose barb to hook
up the hose that routes to the charcoal canister. Some alloy valve covers have a thick boss cast
somewhere inside the sidewall, or on the top, just for this purpose.

Note on the original valve cover that the hose fitting has a restrictor brazed on it's end. It's there to:
a) control crankcase vacuum. b) act as a spark arrestor in the extremely rare (but disasterous) event
that there is a flashover inside the crankcase (basically, it prevents any flame front from traveling up
into the charcoal canister - which is filled with raw fumes). Also, without the restrictor, you'll upset the
carburettor mixture strength (towards lean). You can reproduce a similar restrictor in the new hose
barb by brazing a plug in the hose barb and drilling a new hole of the same size that's on the stock cover.

My advice: If the stock valve cover is badly beat - get another one at a wrecker, or eBay. Throw on a
fresh coat of paint and new stickers.

Save the big money for a spare alternator, fuel pump, clutch & brake cylinders, etc...as you'll be
needing them more vitally than any expensive decorative accessory.
Daniel Wong

This thread was discussed between 17/12/2001 and 19/12/2001

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.